DIY pool maintenance in District 12 - DIY pool maintenance in District 12

DIY Pool Maintenance in District 12

Please send any comments and questions to


This guide is for you if: The goals of this guide are:
  1. Give you a realistic idea of exactly how much work you are signing up for.

  2. Give you a realistic idea of the cost you must pay, if you are paying.

  3. Give you a realistic idea of how good a job you (or even the so-called local "professionals") can do given the pool maintenance equipment available to you.

  4. Introduce you to the very very basics of pools and their plumbing.

  5. Introduce you to the very very basics of pool chemistry.

  6. Point you to excellent online learning guides from the US for DIY pool maintenance, letting you know which parts of those guides you will have to disregard because they assume you have access to equipment that you do not.

I went through the complete learning process between May 2021 and December 2021 in an apartment in Hoi An, Viet Nam. Much of what I learned applies to any South-East Asian country and probably most developing countries in the world, where some critical "standard" equipment found in District 1 is simply not available.

This guide has all the things I wish someone else had told me! Hope you find it helpful.

The Top Myths of Pool Maintenance

First let me save you weeks or months of wasted time and money by exploding some of the common myths of pool maintenance that beginners and even some "professionals" believe in.

These first principles apply to pool maintenance world-wide.

MYTH #1: Pool maintenance is just skimming leaves and dumping in chlorine

In order to keep pool water safe for swimming and safe from forming deposits that can destroy the pool wall, plumbing, and/or pool pump, you need to monitor several different chemical levels, not just chlorine, and you need to add several different kinds of chemicals, not just chlorine.

You don't need to understand the details yet, but here's a typical (and bad) test kit that measures Total Chlorine (TC), Free Chlorine (TC), pH (a measure of whether the water is acidic or basic), alkalinity, cyanuric acid (CYA), and water hardness, which you could consider the bare minimum needed for safe pool maintenance:

You will be adding a form of chlorine sometimes, adding acids at other times, and occasionally adding other substances like baking soda or sodium carbonate.

Which chemicals you add, and how much you add, depends on the results of the measurements you take. There is not a simple one-to-one relationship between measurements and chemicals. At some point you will need to use a "pool calculator" where you type in the current measurements, tell the calculator what change you want to see in those levels, and the calculator tells you how much of which chemicals to add.

Although eventually from your experience you will be able to do fewer measurements on a day to day basis, and sometimes choose chemicals to add without consulting a calculator, you will sometimes need to take the full set of measurements and make non-obvious adjustments using the calculator. Any pool "professional" who tells you they can all do it in their head is either ignorant, lying or deluding themselves.

You will also need to learn about the interactions of measurements and chemicals. For example, if a level like Free Chlorine or pH is way off, it causes several of the other measurements to become invalid, giving you misleading results. You have to correct that level first, measure again, and then work on the other levels.

If you try to "simplify" pool maintenance by ignoring most measurements above, you will eventually get a pool whose water is either actively harmful to swimmers, harmful to your pool plumbing/pumps, or both. You are playing a game with the health of the people using the pool.

If you live in District 12, chances are you only have access to water test kits that let you do some of the basic tests above, and with very poor accuracy. Later in this guide, we will offer some advice about how to best handle this inconvenient truth.

MYTH #2: Pool maintenance is just following a regular schedule

Pool maintenance cannot be simplified down to "put X ml of chlorine in every day, put Y ml of acid in every week." Anyone who tells you so is dangerously uninformed. This kind of "dead reckoning" is almost guaranteed to lead your pool to a state where it has a dangerously high or low pH or Free Chlorine level.

The reason is that environmental factors like the amount of sunlight hitting the pool water, the water temperature, and the amount of dust, pollen, tree leaves and other junk falling into the pool have massive effects on the levels, and these vary day-to-day and season-to-season.

Those levels are also greatly affected by how many people swim in the pool and what...substances they leave behind.

MYTH #3: I can tell the levels just by looking

A pool with a dangerously high or low pH or Free Chlorine level looks, tastes, and smells the same as a pool with safe levels.

Even the famous "chlorine smell" that poorly-maintained and over-used cheap motel pools tend to have is not actually the smell of chlorine at all: it is the smell of a by-product of used-up chlorine and its presence or absence does not tell you anything about the current concentration of chlorine in the pool.

You need a proper test kit to know the levels of all the important chemicals (not just chlorine but pH, alkalinity, and other levels).

If the pool has low chlorine, then bacteria and other nasties that can harm you will start growing in the pool before the pool water turns green and before there is any noticeable smell. Remember, your pool is like a big recirculating bucket of standing water that sits in sunlight all day, with leaves and pollen falling in, insects dying in it, and geckos and birds pooping in it, and the pool filter cannot filter out many of those nasties.

If the pool has very high or low pH or very high chlorine, people with sensitive skin might notice skin or eye burning, but other swimmers may not notice and there can be long-term negative effects on skin and hair.

This shit is serious. If you care about your kids or loved ones who will swim in the pool, don't whisk this away with wishful thinking.

MYTH #4: Pool "professionals" all know this stuff

It is tempting and easy to assume that if you leave this all to the "professionals," you are safe. Sadly, that is not necessarily the case, either in the District 1 or in District 12. As far as I know there is no meaningful certification program for pool "professionals" in the US and Europe and there is definitely none in Viet Nam or Thailand.

Pool "professionals" are usually just random people (often teenagers) who usually make a good-faith effort to dig up the relevant info from

Sorry to be grim, but that is the actual situation when it comes to how pool "professionals" can be trained.

It doesn't help that a dangerous pool often hurts people after a delay, so incompetent pool "professionals" are not immediately weeded out. As long as they can keep the water blue, they can probably keep their job even if the water is toxic.

I'm sure in the District 1 there are "professionals" associated with large pool supply/service companies where there is a stronger economic incentive not to get sued, but on the other hand such "professionals" also have an economic incentive to either under-service the pool (if they charge by hour) or over-chemicalize the pool (if they charge by chemicals) so it's not perfect either.

In District 12s like Viet Nam or Thailand, pool "professionals" tend to spring up in areas with high tourism and thus lots of pools, and they are usually making their best effort to figure this stuff out despite the above problems combined with a huge language barrier. Knowledge is passed by word-of-mouth and professionals only do the subset of tests that are available locally (more on that later).

So you should not assume that a "professional" will be able to do a safer job than you if you do your homework. And in District 12, I think in most cases you can do a much safer job yourself, because the knowledge and standards are simply not there yet.

It is definitely true that in the District 1, we expend massive legal and mental efforts worrying about a lot of stuff that turns out not to carry a risk that is anywhere near proportional to the sacrifice we make to protect ourselves from the risk (e.g. most OSHA safety regulations, many building codes, many traffic regulations, ...). Spending more than a few weeks in a District 12 like Viet Nam or Thailand offers an existence proof of this. However, it turns out that certain dangers are real and the mitigation efforts for them are worthwhile. For example, wise people in District 12 do not drink the tap water (if they can afford not to) and there are real health consequences if they do. I believe proper pool maintenance is more like the tap water case than it is like the building code case.

One thing to take notice of is how often local "professionals" in District 12 will solve pool problems by completely emptying and re-filling pools—something that is illegal in many parts of the District 1 due to water conservation laws. This is one symptom of the incomplete knowledge that they have to work with, and possibly also of the incomplete measurement tools they have to work with. It "works" in some sense, but only when they can tell something is wrong, which isn't always the case, as we explained above.

MYTH #5: The hotels all know this stuff

Mostly, hotels in District 12 use the services of local "professionals" so you are getting the same imperfect knowledge.

The most extremely large and expensive hotels might be able to afford imported pool equipment where all of the pool water measurements, and all of the adding of pool chemicals, are done automatically and continuously by computer algorithms inside a big black box that came with the pool. The hotel then just needs to keep the reservoirs of test chemicals and pool chemicals full and let the computer deal with the details. But you cannot afford such a system (yet), so that doesn't help you.

MYTH #6: The pool shop guys all know this stuff

Pool shops selling pool equipment and supplies in the District 1 always present themselves as the truly "professional" source of truth, attempting to place themselves on a level above the sea of uncertified "pool boys."

But if one thing is crystal clear after reading case after case that gets reported on the better pool forums, with detailed accounts of what the pool shop told the poor pool owner to do, followed by the resulting disaster, followed by corrective action from the actual clueful people on the forums, the average pool shop dispenses much more bad advice than good.

Pool shops in District 1 offer the service of measuring your water sample for all sorts of levels (not just the 6 above but many more) and giving you advice on what chemicals to add. And, wouldn't you know it, you are often advised to add much more of certain chemicals than you need, as well as a lot of magical, expensive "anti-algae chem-clean new-age flocculant ClearPool Clarifier plus XL2" which doesn't do anything at all or may actually harm your pool. Then it turns out you need a sequence of other expensive chemicals to un-do the bad side effects of the earlier chemicals that they sold you.

It seems clear that despite their opportunity to be an actual source of truth, pool shops in District 1 have been utterly corrupted by their commercial incentives to the point where their advice actually has negative value.

Pool shops in District 12 like Viet Nam and Thailand suffer a bit less from this issue because they don't have a lot of these magical chemicals available to sell, though there is still some snake oil to be found. But, more importantly for you, their owners are likely to draw from the same imperfect word-of-mouth chain of knowledge as the local pool "professionals" so it's best to treat their advice with some skepticism as well.

MYTH #7: The pool chemical vendors all know this stuff

Moving back one step in the supply chain, you might think that the pool chemical vendors might know their stuff or have helpful advice for you.

Unfortunately, the vast majority of pool chemicals being sold in the District 1 are either snake oil repackaging of existing chemicals, or they "work" in the short term but have such awful future side-effects on the long-term chemical stability of your pool that you are better off not using them at all. This applies to nearly all chemicals labeled as "algaecide," "floc/flocculant," or "clarifier."

In reality, you can maintain a pool safely with a small set of chemicals which are simple (thus unprofitable to sell), most of which are easy to find in grocery and hardware stores both in District 1 and in District 12 (e.g. baking soda, unscented pure liquid household bleach, borax, and soda ash). One of the better non-commercial websites about pool maintenance, Trouble Free Pool, has a well-organized range of blog posts laying out the case for household chemicals.

In District 12, those chemicals which are recommended by the best DIY sites and which are not readily available in grocery/hardware stores are often available in a nice, simple, unadulterated form in pool shops. So you can buy them with more confidence and likely save money compared to grocery/hardware stores as well.

Certain chemicals recommended by the best DIY sites, like cyanuric acid (aka CYA, stabilizer, conditioner) are not available in District 12, and we'll discuss how you can handle this below.

MYTH #8: The forum people all know this stuff

There are a ton of internet forums and groups about pool maintenance.

There are thousands of keyboard warriors masquerading as experts who provide confident-sounding answers that even I, as a complete beginner with only 7 months experience, can now see are complete bullshit. Some of them are confused about the basic concepts and some of them are just throwing out meaningless terminology.

Save yourself some time and focus on the better, non-commercial pool maintenance forums like the one at Trouble Free Pool and even then take note of which users on the forum have the longest history (and also wrote many of the guides on the same website) and seem to be giving out sensible advice that is based on actual chemical knowledge. There's still a lot of confident nonsense posted even on the best forums.

The reality of pool chemistry is that every model of it is an approximation, and forum posters who are honest and up-front about this are to be trusted more. Forum posters who make blanket absolute statements about the FC/TC/pH/Alk/CYA measurements telling exactly this at all times are not to be trusted.

In reality the model that most good pool professionals and the better users on forums use, which based on those 6-8 measured chemical levels and fairly-well-agreed-upon pool calculator formulas telling you what chemicals to add to change the levels, give you a high probability of keeping your pool balanced and safe. The models necessarily simplify the dazzling variety of different substances that might fall into your pool, and simplify the ways in which the chemicals can interact, but they work pretty well.

Some District 1 companies advertise and offer more complex complete "pool maintenance systems," along with a product line of either chemicals or services or both, often accompanied by hours and hours of chemistry-terminology-laden YouTube videos. To me it looks like the standard system, wrapped in a proprietary shell of obscurity to lock you into their products like Apple does with its products. I could be wrong about that—maybe they do have some insight that can lead to better pool results than the standard system—but my instinct says no.

You should consider the system of 6-8 measurements and 3-4 chemicals described in this guide to be the minimum viable system. You cannot safely get away with "simplifying" pool maintenance down to "just chlorine and pH" as many "professionals" in District 12 wish to do, because, as with drinking contaminated water, the consequences do matter.

MYTH #9: The YouTubers all know this stuff

There are a ton of mostly amateur YouTube channels covering pool maintenance that conflict with each other, and often themselves, in the most fundamental ways, just as the posts on the forums do. Some YouTubers even show themselves dropping toxic cancer-causing testing chemicals into the pool right before their children swim in it.

One pretty good channel, whose commercial incentive is to sell online teaching materials rather than to sell services or particular chemicals, is Swim University. They have some excellent and entertaining videos that cover the basics. They are not as passionate about DIY and household chemicals as Trouble Free Pool but their videos are still a great place to start learning.

As we will explain later, all the best online guides and YouTube videos assume you have certain chemicals and tools that are not actually available in District 12s like Viet Nam and Thailand. So you need to work around this in ways we will describe below.

MYTH #10: I know this stuff

I am a total beginner who has only been at this for 7 months and who has never actually been able to take a proper measurement of certain key quantities like alkalinity or water hardness due to the lack of available equipment (more on that below). So I have never actually done "proper" pool maintenance as described in the best DIY District 1 websites like Trouble Free Pool. I would not be qualified to maintain a pool in District 1 because I don't yet have experience with complete measurement kits. However, the tools I have available here are the same ones you have available in your District 12.

I did do my homework in terms of research and I made it my science project to stretch the available gear to its absolute limit. I calibrated my pH meter with buffer solutions and double-deionized water and I wrote a custom computer program to analyze the OTO chlorine measurement color, digitizing each OTO measurement in constant lighting conditions, to extract the most precision possible from this extremely limited tool. This at least allowed me to sanity-check that my methods were working as much as possible. And we were able to use the pool for 7 months without medical issues.

How Much Work Is It?

So what are you committing to when you decide to maintain your pool?

Step 1: Education: As explained above, this stuff is not trivial. Figure on spending a minimum of 20 hours watching YouTube videos and reading online guides about pool maintenance. And, in the likely event that your landlord doesn't know anything about how your pool works, figure at least another 5-10 hours of trial and error as you try to work out exactly how your pool is plumbed and find hidden gotchas (e.g. non-obvious drain pipes, clogged filters, malfunctioning backflow prevention valves). Below we will offer some guidance to accelerate your understanding of your pool's plumbing.

Step 2: Pool Shock: Most likely your pool will start out as a green swamp. You'll need to do a 2-7 day process known as shocking the pool which involves spending roughly 1-2 hours per day vacuming the pool and adding lots of chemicals until the pool turns clean blue. If your local laws allow it, you could also empty, scrub, and refill the pool over a few days, but even so you will need to add chemicals to bring it to stable levels and this may take several days of trial and error. My pool took 4-5 days to shock:

Step 3: Regular Maintenance: As we explained above, pool maintenance is never as simple as dumping in fixed amounts of chemicals at fixed intervals. Instead, the picture looks more like this:

If you diligently keep up with all these tasks, then this is a realistic idea of how much time you will need to spend.

But, if you are lazy/forgetful and flake out on your tasks for more than a few days, the pool will punish you by turning green again, and you will have to go back to Step 2, costing you much more time.

How Expensive Is It?

If you own the pool, or your landlord refuses to pay for the pool supplies needed to maintain the pool, or your landlord understandably wants a cost estimate before agreeing to let you revive the pool, you'll need an estimate of price for supplies, chemicals, and electricity.

One-Time Costs

If the pool has been abandoned for a while, you will probably need to replace some of the tools that cracked in the sun or got lost, like the pool skimmer or vacume pipe. On your local "Amazon" (Lazada/Alibaba, in the case of Viet Nam and Thailand) you can find a manual skimmer for around USD $10-15 with 20-30 day delivery from China, or if you are in a hurry you will pay 4-5x more if you buy in local pool shops. You will definitely also need to buy new rubber gloves, masks, and eye protection, call it USD $10 for those.

You will need to buy water test kits and equipment. We will talk more about this below but the selection is extremely limited, so much so that it actually prevents you from doing a decent job. Anyway, the "standard," awful OTO/phenol red chlorine/pH test kit is around $15 and will last you a few months, and as we will discuss more below, you will likely also want an electronic pH meter and buffer powder and deionized water for calibration, which costs around $10 (and the deionized water will require some time-consuming sleuthing to locate).

Another important thing to consider is: what if you break the pool? How much is it to replace key components and who will pay? It's worth spending a few minutes looking at your local price for the most expensive components, namely:

and discussing the issue with the pool owner. The pump and filter prices are likely even higher in District 12 than in the District 1 because these parts are often imported. This could be hundreds or thousands of USD.

Note that the pool might already be broken before you started messing with it, but this might not be obvious to anyone. Your landlord will need to trust your integrity if you are to avoid being charged for problems you didn't cause.

Recurring Costs

The actual price varies wildly depending on: Rather than presenting a specific number in this guide, we will present an example calculation and you can do a similar calculation with your local prices once you understand your needs.

Don't underestimate that last factor above: if your pool filter is clogged up or channeled, this may cause it to filter out much less stuff, which not only threatens your safety but also may cause you to need to run the pump for much longer, eating electricity, or cause the pool to eat a lot more chlorine (since the chlorine will continually react with organic materials that the filter failed to remove) and perhaps even cause extra wear to the pump that will speed its demise as well.

Especially in District 12, you are likely to run into landlords who employ short-term thinking. They will see that it costs $44 to replace the filter material now, but only $5 to buy more chlorine now, and will choose the $5 every time, even though paying $44 to replace the filter will pay for itself in months and then continue to pay dividends for years. You might not be able to counter this short-term thinking with logical arguments, so be ready to price out a less-than-efficient scenario too.

You can estimate some of the recurring costs before you purchase the first chemical. But to get even rough ideas of some of the recurring costs, you will need to try running the real pool for a few weeks to measure how fast the pool eats your chemicals or power—there are too many variables to anticipate beforehand. Be sure to set your landlord's expectations about that. Fortunately, in District 12 (thanks to all the short-term thinking) you can likely buy very small quantities of chemicals first in order to determine your burn rate.

One important thing to be aware of is that in the District 12s where I have checked (Viet Nam and Thailand), the price of all service and most chemicals is significantly less relative to your cost of living than it is in District 1. A lot of guides and YouTube videos about pool maintenance assume a relatively high cost for chemicals, and so they may say that certain chemicals like cyanuric acid (aka CYA, stabilizer, conditioner) are "essential" in part because they allow you to purchase less of other chemicals like chlorine. That logic works for District 1, but might not make sense for District 12, even if you do happen to have CYA available there (if CYA is available, its cost will be extremely high because it is likely imported, whereas chlorine/bleach is local). So be sure to cost out all your alternatives and don't be surprised if your best deal is different than what the District 1 videos say.

In Hoi An, Viet Nam, with my small (28,728L (7,589G), 2.6m x 7.2m (8.5ft x 23.6ft)) "infinity" pool, which is about 2/3 under shade and about 1/3 exposed to the sun (but where we cover the sunny part with a tarp when not using the pool, which reduces the chlorine costs significantly):

the recurring costs during the hot months of the year (May-Sep, when the daytime temperature is regularly more than 32C (90F) and often more than 37C (100F)) looked like this:

So in my case the recurring costs came to roughly $54/month.

You will note that all these prices are laughably low compared to District 1.

Also note these prices do not include any stabilizers (aka CYA, conditioner, Trichlor, Dichlor) because these chemicals are simply not available in District 12 (or if we could find it, the imported price would definitely not be worth the "savings" in Chlorine).

Should I DIY?

Here in my District 12 (Hoi An, Viet Nam) the pool "professionals" charge $50/mo for an ongoing service where they clean and check chemicals 2 times per week, including the cost of chemicals, or $66 for the same service but 3 times per week.

Note this "professional" service does not include any periodic pool shocks after the first one, nor does it include any filter material replacement. Most likely if they encounter any problem, they will drain and refill your pool, which for the example pool costs $11 of water (except during Hoi An's frequent droughts when water may cost 2-4x as much) and approximately $3.18 of electricity per 24 hours to pump that water into the pool (assuming a 1kw pump and baseline electric usage).

Even given the service limitations, clearly you should not DIY for cost reasons. The service is just too cheap to justify that.

If, however, you:

then yes, you should DIY. Especially if the people who will be swimming are aware of your status as an inexperienced, unpaid learner and are tolerant of delays.

You might think "in all cases it would be better if the landlord just did their job and hired the professional." But unfortunately, as we explained above and will detail below, having the "professional" service is not necessarily the safest option.

If you are looking for an easy, spoon-fed, regular regimen of leaf-skimming and chemical dumping that will allow you to swim with minimal effort, do not DIY. You're likely to get the pool into an unsafe state, and also frustrate yourself, so you're better off using the imperfect services of the local "professionals."

OK, I'll DIY! How does a pool work?

First we're going to introduce some bare basics about pool plumbing that I wish someone had explained to me. I spent weeks of trial and error really discovering how my pool was plumbed, with a few additional surprises that partially drained the pool (caused by faulty valves hidden inside pipes) coming in subsequent months. If by some miracle you have a manual for your pool in a language you can read, do it!

Then, we're going to explain the pool chemicals and chemical test kits that are the most fundamental, essential, basic minimum for pool maintenance in District 1, and then pull the floor out from under you by telling you which test kits you have access to and how limited they are. And we'll go over how you can muddle along.

Then, we're going to point you to some great online guides and videos about pool maintenance and let you know which parts will not apply given your limited tools.

Basic Pool Plumbing

Ins and Outs

First thing to figure out is all the ways water can get into and out of your pool (blue arrows indicate direction of water flow):

In this example pool,

Valves and Air: Keeping Your Pump Alive

As we'll see later, there are valves you can turn to start or stop water from flowing into the return jets (R), and to start and stop water from flowing out the main drain (D) or vacume port (V). Whether or not water spills over the edge (T) is simply determined by whether or not you are pumping more water in through the return jets (R) than you are pumping out the main drain (D) and vacume port (V) combined.

The first principle of pool plumbing is to never ever turn on your pump when there is not some way that water can flow through it unimpeded. For example, after doing some maintenance, if you forget to re-open the valve that blocks the return jets (R) and turn on your pump, that's a great way to burn out your pump in seconds as the pump tries to push the water against the closed valve. If you do this, your pump will let out a horrific noise to let you know it and you better react fast.

A great technique is that every time you are about to turn on the pump, see the path of water in your mind and actually trace it throughout your pool and double-check that all valves are actually open along that whole path.

The second principle of pool plumbing is to never let your pool pump pump air. This can also burn out your pump quickly. For example, imagine that you want to vacume the pool, so you plug the vacume hose into the vacume port (V) while the vacume hose is full of air, then turn on the pump. The pump will suffer and maybe die as it tries to suck the air out of the hose. Instead, you want to watch a fun video like this to learn how to fill the pipe with water first. More on vacuming below.

Ok, so now you know what all the holes in your pool are, but where do all these holes go?

The Maintenance Cave

Somewhere in your pool setup, possibly at pool level off in a corner or shack, or in a mysterious underground (well, below-pool-level) maintenance cave, as the red arrow indicates in the example pool here:

you will find a setup with a pool pump (P), a pool filter (F), and the distinctive multi-port valve (M):

This warped panorama shows all the pipes and equipment at once:

Let's follow the path that water takes through the system.

Pool Outputs, Pump Inputs

Notice how there are three pipes that come together and go into the input (I) of the pump: there is the pipe that comes from the main drain (D), the pipe from the vacume port (V), and a third pipe, which we will explain later, that carries the water that spilled over the pool's infinity edge (E). So we see all three ways that water can come out of the pool come together here and go into the pump. Each way has its own big red valve.

The Pump and Strainer Basket

Notice how the pump itself (P) has a clear plastic window, under which is a white strainer basket. This basket collects all the large debris like rocks and large leaves that comes in. The strainer basket is not the same as the pool filter. The strainer basket catches big stuff and the filter catches fine stuff. You will need to periodically open the plastic window and empty the rocks and other gunk that collected in the strainer basket.

The third principle of pool plumbing is to never go and open a port for water to escape, such as the clear plastic window in the pump, if the entire weight of 28,728L of water from the pool is bearing down on it, because you're not going to be able to screw the plastic window back on and you're going to empty the entire contents of the pool in your little maintenance cave until the water level either spills out at ground level or reaches an electrical wire and kills you. That would be bad. So, before opening any such port, be extra sure that you have closed all valves on both sides of the pump (remember, water can flow backwards through the pump when it is not on). Just close every valve in sight and also turn the multi-port valve to closed (more on that below). Assume that some valves may fail and that two blockages are safer than one.

The Filter

Ok, now notice how the output of the pump (O) is connected to the multi-port valve (M). Your pool will have a multi-port valve if your pool has a sand or DE filter. The example pool has a sand filter. If your pool uses (paper) cartridge filters, you might not have a multi-port valve and you will need to research yourself how to clean/replace the filter.

We'll get back to what the multi-port valve does in a second, but notice what else is connected to the multi-port valve: the pipe leading to the return jets (R) that spew water back into the pool, as well as a waste pipe (W), which leads out into the street in front of the apartment, where unsuspecting bicyclists are going by and minding their own business. The waste pipe (W) is used to discard icky, gucky dirty water that we are flushing out of our filter or that we are vacuming from the bottom of the pool. Poor bicyclists.

The gigantic grey tank underneath the multi-port valve (M) is the filter (F). The filter is basically a big pile of sand. During normal filtering operation, dirty water coming in from the pool (D, V, and E) which has just gone through the pump (I and O) is pushed into one side of the tank. The water must push its way between the grains of sand, thus being filtered, before it can escape the other side of the tank. It's really hard for water to make it through the sand since the sand is so heavy, which is why the sand filters well. The filtering operation, not the actual pumping of water through the pipes to and from the pool, consumes almost all the energy of the pump, and the filter tank is under so much pressure that it actually balloons up a bit when running.

The Multi-Port Valve

So basically everything is connected to the multi-port valve (M), including the filter (F). The multi-port valve is a piece of pure genius that lets you interconnect these pipes and the filter in various ways depending on what you want to do. Watch this excellent and entertaining video which shows you all the different configurations you can choose just by turning the handle at the top of the multi-port valve:


The video above talks about backwashing and rinsing. Backwashing+rinsing is something you must do periodically (perhaps every 1-2 weeks) in order to keep the sand inside the filter clean by running water backwards through the sand. This is a great time to learn about that:

Normal Filtering Operation

Now we have seen the complete path that water takes when it leaves the pool (via the main drain (D), vacume port (V), or infinity edge (E)), goes through the pump (I and O), the multi-port valve (M), and (assuming the multi-port valve is in its usual "filter" position) back into the pool return jets (R).

When you are running the pool in its normal filtering mode (with the multi-port valve (M) in the "filter" position), how should you set the three big red valves that connect or disconnect the main drain (D), vacume port (V), and infinity edge (E) from the pump (P)?

Well, since you are not vacuming, you should probably close the valve from the vacume port (V). There's not much benefit to that port sucking water in near the top of the pool and a kid might even hurt themselves if they stick their fingers up to the port since it is so powerful.

You can then choose what to do with the main drain (D) valve depending on what you want to do. If you want the pool to spill over the "infinity" edge, then close the main drain (D) valve. The water will have no choice but to spill over the edge since there is no other way out of the pool. If you don't want to use the infinity edge, open the main drain (D) valve. Water will go out the main drain, which is plenty big to suck down all the flow of water coming in the return jets (R). We'll talk more below about what you should do with the infinity edge (E) valve in these cases.

Is it better to run the pool with the infinity edge or without it? It doesn't really matter that much. Just do whatever is fun. With the infinity edge running, the pool will automatically push all the small leaves and dead bugs off the pool surface and into the trough around the edge of the pool so you don't have to grab them with the manual skimmer. Score one for laziness. But, with the infinity edge running, the water in the pool is being aerated more, and this causes the pH to go up faster, meaning you'll probably need to add acid more often (more about that later). Not a big deal though. And, over the long term you will want to run the infinity edge sometimes because it is part of the magic that replaces water in the pool after the sun evaporates the water away...more on that later.

How about when you are done using the pump and you want to turn the pump off for one or more days? How should you set the three big red valves that connect or disconnect the main drain (D), vacume port (V), and infinity edge (E)? Well, the system is designed to let you be lazy and leave them either closed or open without Bad Stuff happening when the pump is off.

Unfortunately, the system in the example pool is broken, as we will explain more below. Because a one-way valve from the infinity edge (E) is intermittently malfunctioning, in the example pool it is necessary to shut off the big red value for the infinity edge (E) every time you shut off the pump, otherwise you'll occasionally wake up the next day with a rude shock where half the pool water (yes, half of 28,728L) has seemingly vanished into thin air. Not only was it not obvious that the one-way valve was the cause of the problem, but the one-way valve itself is almost hidden (it's inside one of the pipes and looks like a normal junction in the picture) and I had to deduce its existence by thinking about why the pool doesn't always empty out when I shut off the pump. This is a classic example of the kind of thing that will go wrong with your pool and will occasionally require you to spend 8 hours tearing your hair out trying to figure out what is going wrong. You might even need multiple 8-hour sessions: before I realized the one-way valve existed and was faulty, I went down two other wrong paths about why the pool kept emptying itself out and my "fixes" for those didn't work. If you want to DIY your pool, assume you'll need to occasionally spend significant hours debugging mysterious problems like this. It comes with the territory.

Vacuming the Pool Floor

Every week or two, you will clean the bottom of your pool using a pool vacume setup like this:

Now is the right time to learn more about how that works:

When it comes time to vacume your pool, you will want "maximum suck power" from the vacume port, so you should open the big red valve that connects the vacume port (V) to the pump input (I), and close the big red valves that connect the main drain (D) and infinity edge (E) to the pump input (I). Also, as explained in the video above, don't forget to set the multi-port valve (M) to "waste" so the nasty water empties out the waste (W) pipe to the street rather than going through your filter again and/or back into the pool.

The video above shows you a trick to fill your vacume hose with water using a return jet so you can make sure the pump never sucks in air. If your return jets are located on the bottom of the pool, as in the example pool here, the trick they show won't work. You can achieve the same effect by using your long pool pole to push the vacume head against a return jet on the bottom of the pool, while the other end of the vacume hose is sitting disconnected on the ground just outside the pool. After a few seconds, tons of water will start spewing out of the disconnected end of the vacume hose, and then it is safe to connect that end to the pool's vacume port.

Infinity Pool Plumbing

We have handwaved away one extremely important component of the system. We mentioned that water spilling over the infinity edge goes into a big trough (T) around the edge of the pool:

and we mentioned that water from the infinity edge feeds into pipe E, which is connected to the pump input (I) in the maintenance cave:

But T and E are not directly connected by a single pipe...they cannot be. Imagine if we start up our pool pump with the pool water level slightly below the edge, and therefore no water in the trough. It actually takes a minute or two of pumping for water to rise up and over the edge. If the trough (T) were directly connected to pipe E, and thus the pump input (I), then that would mean the pump would be sucking air through pipe E for a long time, which could destroy the pump, as we mentioned above.

The Infinity Cave

In reality, between the trough (T) and the pipe E in the maintenance cave, there is actually a whole other cave, which I affectionately refer to as the "infinity cave:"

The infinity cave is at the same level as the maintenance cave, with its floor several meters below the pool and its ceiling about 15cm below the pool edge.

Water that goes over the pool edge and into the trough spills in through the large pipes (T) and dumps into a reservoir formed by the infinity cave. The reservoir is approximately 2m x 2m (6 feet x 6 feet), so it is much smaller than the pool, and it can fill up to about 1.5m (4 feet) max.

Water then leaves the infinity cave reservoir through a pipe near the floor (E), and this is the same pipe (E) that we saw sticking into the maintenance cave and going into the pump (I).

The Infinity Cave Reservoir

The infinity cave reservoir serves several functions.

First, as long as the infinity cave reservoir's water level never goes below the level of pipe E, the pump will never suck in air. It is your job to make sure this never happens. You can accidentally make it happen quite easily: if you run the pump with valve (E) open, meaning the pump is happily sucking water out of the infinity cave reservoir, but the pool level happens to be lower than usual, meaning it might take minutes or hours for the pool to fill up and start spilling over the edge, then you will quickly reach the point where the water level in the infinity cave reservoir goes below pipe E and the pump is sucking in air.

So every time you run the pool pump with valve E open, you have to think about this sort of thing. You have to develop a mental model about what will happen with the water level in the pool vs. the infinity reservoir. Sometimes it's not at all obvious because it's not clear which incoming flow of water will "beat" the other. For example, when the pool is completely filled up and only a few centimeters away from spilling over, and the reservoir is mostly full, you are safe. The water in the infinity cave reservoir will be enough during the minute or two it takes for water to start spilling over the infinity edge and replenishing the infinity cave reservoir, so the pump will never suck in air. But if the pool level is even just 5cm below the edge, the small infinity cave reservoir is not big enough to ride over this long "drought" of incoming water. You will need to occasionally turn off the pump and let the infinity pool reservoir refill itself (more on refilling below).

Be careful about this. If you leave the pool unattended while the pump is running and valve E is open, you may easily end up making the pump suck air through pipe E and walk back in to find a dead pump. When you are first getting to know the pool, it's important to stay with it and watch the levels in the infinity cave reservoir and make sure they are doing what you expect.

The Infinity Cave Float Valve

The second purpose of the infinity cave reservoir is that it is a convenient and clever place to automatically add tap water to replace water that the sun has evaporated away.

Inside the infinity cave there is also a float valve (Q):

Whenever the infinity cave reservoir water level falls below the level of the rubber ball, new tap water from the city flows in (slowly but surely) to fill the infinity cave reservoir up to the level of the rubber ball again.

It is a coincidence that the water from one of the trough (T) pipes flows over the rubber ball. The important thing is that the ball goes up and down according to the water level in the infinity cave reservoir, and this controls how much tap water pours out of the float valve.

Reasoning about the Infinity Cave Reservoir

Once you know all the parts involved, it is a bit of a mindfuck to reason about how the infinity cave reservoir actually works. Quickly you find yourself asking:

These are great questions and the answers are not obvious. Those who like puzzles are invited to stop here and try to think of the answers.

First, the level of the pool and the infinity cave reservoir don't have to be the same because the pool spills over into the infinity cave reservoir. And the pool only spills over when the pump is running and pushing water into the return jets (R). And when the pump is running, the pump is pulling an equal volume of water out of the infinity cave reservoir through pipe E (assuming the main drain (D) valve and vacume (V) valve are closed). So in the steady-state, the infinity cave reservoir level stays the same, because every liter of water the pump takes away through pipe E gets replaced by a liter of water spilling down from the pool through the trough T.

If you are extremely clever, you are already thinking about the following scenario: imagine that you are running the pump in the steady-state described above and you turn off the pump, leaving everything else unchanged. A pump that is turned off acts like a pipe (water can flow past the pump's stopped impeller, albeit slowed down a bit). So, in that case the pool and the infinity cave reservoir are connected and, given enough time, they will equalize! This means that the infinity cave reservoir is definitely going to rise up and spill out somewhere. Why doesn't this happen?

Well, it turns out that there is a one-way valve hidden inside pipe E. You can see it here:

This one-way valve prevents backwards flow from the pool into the infinity cave reservoir via pipe E (through any of the pipes meant for flow in either direction, whether that be the return jets (R) or the main drain (D) or the vacume port (V)). So the one-way valve prevents the pool and infinity cave reservoir from equalizing when the pump is off, and politely steps out of the way when the pump is on.

Except, in the example pool, it sometimes doesn't, because the one-way valve is faulty. Every once in a while, I would turn off the pump, leaving valve E open, but—without me being aware of it—the one-way valve would stick slightly open, allowing water to seep from the pool into the infinity cave reservoir. Overnight, the pool would slowly equalize and the water level in the infinity cave reservoir would rise and rise and rise (targeting the pool level itself, initially 1m higher). In the worst incident, the pool lost half its water, more than 14,000L, far more water than the entire infinity cave can hold. What's worse, the next morning when I was frantically trying to figure out what happened, I couldn't find where the water had gone! The infinity cave top was totally dry, there was no water in the street, no water had spilled out of holes in nearby bricks or was just gone! I thought there must be some mystery cavern under the pool that I had completely filled up with pool water—perhaps a secret speakeasy with rice whiskey, roulette and poker tables. After much investigation and many false starts, I discovered that hidden under the lip of the infinity cave there is a tiny (less than 1/2") plastic pipe which heads off in a completely odd direction where no other pool pipe heads, runs underground clear across the property to the other side of the 3-story 6-apartment building and spills out in the swamp behind the apartment. Why didn't they run this drain down the waste (W) pipe like every other drain in the system? Good God. This is an example of the kind of fun times you will have debugging problems with your pool.

Anyway, we still haven't answered all the questions above.

Why does the pool refill enough, since the float valve is in the infinity cave and not in the pool? Well, this pool is designed to spill, so the strategy is just to keep pumping water into the pool until it spills over. "Refill enough" for this pool means "fill until the pool spills over." It is not possible to fill the pool more than that, and the system is designed to fill the pool to the edge as long as valve E is open. If we kept the infinity edge valve (E) closed and the main drain (D) open, meaning we never ran the infinity edge, then the pool would never get refilled: as the sun evaporates away water over weeks, the pool level would go down and down.

Why doesn't the pool sometimes overflow, since the float valve is in the infinity cave and not in the pool? Well, the pool itself always overflows—it is designed to do so. And the infinity cave reservoir is designed to stop filling itself when its level goes above the level of the float valve's rubber ball. So there is no scenario where things keep filling up indefinitely.

A Conundrum

...Or is there?

Although the infinity cave's float valve will stop tap new water from coming when it the infinity cave's water level reaches a certain point, that doesn't necessarily mean that the infinity cave reservoir never goes above that point.

During normal infinity edge operation, the pool is full to spilling, and there is also quite a bit of water in the trough (T) making its way to the infinity cave. The trough can hold a lot of water because it goes all the way around the pool. Imagine we are in this state and imagine that the water level in the infinity cave reservoir is at the level of its float valve Q (the level at which the float valve shuts off the tap water). Now imagine that we shut off the pump. Water stops flowing into the pool, so the pool stops spilling. But the water in the trough continues to empty out into the infinity cave reservoir until the trough is empty. So the level in the infinity cave reservoir ends up significantly above the level that the infinity cave's float valve "wants" (meaning that the rubber ball attached to the float valve is being pushed up hard by the high water level). This is actually what happens every time we turn off the pool pump after using the infinity edge and it's "normal." Let's call this the shutoff level boost. If the amount of water left in the trough is so much that it would cause the infinity cave reservoir to overflow, then the overflowing water disappears through the aforementioned tiny secret drain pipe and comes out the swamp behind the property. I haven't actually checked if this happens or not.

A one-time effect similar to, but opposite in direction from, the shutoff level boost happens when we turn on the pool each day with the infinity edge on (with valve E open). Let's call this the turnon level drop. Initially, before we turn the pump on, the infinity cave reservoir is at or above the level "chosen" by the float valve Q (it might be above because of the previous day's shutoff level boost). The pump begins to madly suck water out of the infinity cave reservoir through pipe E, but the pool is not yet spilling, so the level of the infinity cave reservoir drops rapidly since the pump is powerful and the infinity cave is not that big. Eventually (usually after 1-2 minutes), the pool water makes it over the edge and starts spilling, and at that point the infinity cave reservoir level stops dropping and stays the same (assuming, for now, that the float valve is not adding more new tap water to the system).

Hypothetically, if the shutoff level boost were equal to the turnon level drop, then these two effects would cancel each other out: stopping the pump would leave the infinity cave water level X cm higher than the float valve level, but then starting the pump again would lower the level X cm back down again. Over the long term, the system would not gain or lose any water.

But that is not actually what is happening in my pool. I don't know if this is because my pool system is still misconfigured or faulty (likely) or because the pool system itself has a design flaw (unlikely, but possible).

Specifically, from my observations, when we turn on the pump and the infinity cave reservoir experiences its turnon level drop, the new, stable water level is far below the float valve level (the level that the float valve Q "wants") even though the infinity cave reservoir started higher than the float valve level due to the previous shutoff level boost. Often when the pool starts spilling over and I peer into the infinity cave, the level has dropped to 50-60% of the float valve level. As soon as the infinity cave reservoir level goes below the float valve level (a minute before the pool starts spilling over), the float valve of course kicks into action and starts adding tap water to the infinity cave reservoir. Even after the pool starts spilling over (which, remember, freezes the level of the infinity cave reservoir, at least if we ignore the new tap water that the float valve is adding), the float valve continues to fill the infinity cave reservoir with tap water. The float valve fills very slowly, but assuming we are enjoying the pool for a few hours, there is enough time to refill the infinity cave reservoir back to the float valve's favorite level.

So this means every time we start the pool up, a pretty significant amount of tap water gets added to the system. The sun evaporates water every day, but not that much water.

So, with water being net added every day, eventually something has to break: something has to fill up and overflow. The pool itself always overflows by design, and its overflow always goes in the trough. The trough cannot overflow because it is connected to the infinity cave reservoir (that is, the infinity cave reservoir would overflow before the trough does). So it must be the infinity cave reservoir that eventually overflows, through the aforementioned tiny secret drain pipe that comes out in the swamp behind the property. I have not actually confirmed that this occurs, but the analysis seems to show that it must occur.

Maybe there is some adjustment I could make to the pool so that this daily wasting of water doesn't happen (assuming it happens). But I haven't yet figured out what that adjustment might be. If I adjusted the float valve to stop at a higher or lower water infinity cave reservoir level, this wouldn't solve the problem, because the amount of water added on each turnon (assuming we swim for many hours) is exactly equal to the sum of the the shutoff level boost in cm and the turnon level drop in cm, neither of which would be affected by changing the float valve's cutoff level. Going through the steps in order: each time we turn off the pool (after swimming a long time), the water is exactly at the float valve level, whatever that happens to be. Then the trough adds the shutoff level boost, and the infinity cave reservoir sits at that boosted level overnight. Then the next day we turn on the pump, which always sucks out the same amount of water (which is determined by how far the pool level is below the pool edge), giving us the same turnon level drop as always. Then (assuming we swim for a long time) the infinity cave reservoir's float value fills it back up to the float valve level (whatever that happens to be). Nothing in that picture changes depending on what the float valve level actually is (well, unless we set the float valve level so low that pipe E sucks air, or so high that water constantly leaks out the drain, but those things aren't happening in my pool).

Right now I am assuming that all the water in the trough is higher than the tiny drain pipe in the infinity cave. I haven't dug up the trough to check its depth. If that assumption is wrong, it means that after a shutoff, the trough also holds a significant amount of water (not just the infinity cave reservoir). But this too doesn't solve the conundrum: I still observe the float valve adding a large amount of water to the infinity cave every time I start up the pump again. It doesn't matter how much water other parts of the system are holding: I see a ton of new water enter the system on each startup.

The only ways out of this conundrum that I see are:

If any readers have insight as to how this actually supposed to work, or think they know a reason why the existing configuration should not actually waste water, let us know!

So as you can see, reasoning about an infinity pool is not trivial, but it's interesting.

Sump Pump

Keen observers may have noticed that in the maintenance cave for the example pool:

There is actually another contraption off in the corner, with its own pipe. This is the sump pump (S):

This pump is not related to pool water at all. Instead, the purpose of this small pump is to pump rainwater that collects in the cave out of the cave and dump it out in the street (and the sump pump is also handy if you make a mistake and dump a bunch of pool water onto the maintenance cave floor). The little red box hanging off of the sump pump is actually a float valve of sorts: when the water level becomes so high that the little red box is floating high above the pump, the pump will turn on and water will flow out to the street until the water level has gone down much lower and the little red box has sunk down significantly.

Sometimes, when you want to work in the cave, you will want to turn on the sump pump manually to completely drain the cave so you can stand in it without getting your feet wet. To do this, just grab a hoe or similar tool and lift up the little red float for a minute until all the water gets pumped out.

You may wonder why, when the pump is finished with its work, all the water in the part of the pipe going to the street that is at the same level as the cave doesn't come rushing back into the cave. That is because there is a one-way valve hidden in that pipe, as indicated above. The one-way valve doesn't work very well (it's not very strong at stopping flow in the "wrong" direction) but since the pressures involved are so low, it works well enough.

Something rather scary is that the sump pump is always on and powered up, even if the circuit breaker for the pool pump is turned off. And the circuit breaker for the pool pump also has a "hot" side that is always powered on as well. That means that if something were go to wrong and if the maintenance cave filled with water (either pool water or rain water), then the water would eventually reach the level of the hot electrical wiring inside the cave and electrocute anyone touching it. Including the case where there is a prolonged power failure while it is raining hard, which happens often in Hoi An. The proper design would be to make sure there is some kind of emergency drain below the level of an exposed hot electrical wiring, but in this example pool, there is not (the emergency drain is several inches above the level of the exposed hot electrical wiring). Just a pleasant thought for you.

Pool Chemistry: The Inconvenient Truth

Now that you fully understand the plumbing, it's time to learn about the chemistry used to keep your water clean and safe.

First we're going to explain the chemicals and chemical test kits that are the most fundamental, essential, basic minimum for pool maintenance in District 1. Then we'll drop the floor out from under you by telling you which chemicals and test kits you likely have access in District 12 to and how limited they are. And we'll go over how you can muddle along.

How It's Supposed to Work

Now is the time for you to learn basic pool chemistry.

The high-level idea is that there are certain levels you want to continually check in your water, known as:

If all the levels are in their proper ranges, it means your pool water is actively protecting you from medical harm (bacteria, algae, fungi, amoeba, etc.), actively making sure the water stays clear and beautiful, and protecting the pool pipes, pump and other plumbing from physical damage (due to corrosion, scale development, etc.).

When one or more of those levels goes awry, it means that you need to add various chemicals to fix it. There's a few tricky things though:

When it comes time to change one or more levels, you will need a pool calculator that lets you enter the current levels and your desired change, and it tells you which chemicals to add and how much. One free online calculator is here (a bit geeky) and here (better) and here (best), and there are also a ton of iOS and Android apps that do the same.

Below we will link to some fun and gentle introductions to some of these basics. First, watch these videos through, keeping in mind that you won't have the tools to do everything in these videos, but the basic goals (in terms of chemical levels) are the same.

On the internet, there are a lot of really terrible, inaccurate, self-contradictory, commercially deceptive, and/or misleading blog and video guides out there. I will save you a bunch of time by pointing you to some better ones and supplementing where they lack.

pH, Alkalinity, and Calcium Hardness

This first video introduces pH, alkalinity, and calcium hardness and the chemicals people use to affect them:

Notice how there's nearly always a household chemical alternative to the fancy commercial chemicals; this is really important for those living in District 12.

This followup video mentions more of the household chemical alternatives:

The one chemical for which he didn't mention a common household equivalent in the video, muriatic acid (aka hydrochloric acid 18% concentration), is almost certainly available from pool shops or other chemical shops in District 12 at a very low price, since this acid is used widely in many industries, so no worries about that one.


The next thing you will need is a pool sanitizer: a chemical which kills bacteria, algae, viruses, and other nasties that may threaten your health.

Although there are pool sanitizers other than chlorine, chances are in District 12 chlorine will be your only choice, and it is also by far the most popular choice even in District 1. If you happen to have a "salt water pool," note these pools also generate chlorine from the salt as explained here.

So you will need to find some source of chlorine. There's a great and short blog post about the alternatives on Trouble Free Pool. Check that out now.

The most common source of chlorine in District 12 is probably calcium hypochlorite crystals, aka cal hypo. These crystals work really well for shocking the pool, but they are really nasty to work with (the odor they spew off is chemically similar to mustard gas) and continued use of them slowly raises your pool's calcium hardness up and up in a way that can eventually be a problem.

In the household chemical video above, Swim University briefly mentions that household bleach "can be used to shock your swimming pool." In fact, many pool DIYers never use solid sources of chlorine like cal hypo and instead exclusively use pure household bleach as their source of chlorine (not only for occasional pool shocking, but also for maintaining chlorine levels day to day). Pure bleach has many advantages over cal hypo: it's less dangerous to work with, easier to add to the pool, and doesn't cause the pool's calcium level to increase continuously.

If you can find truly pure bleach in your District 12, it might be a good alternative. Sadly, in my District 12 (Viet Nam), all the bleach I could find locally and online was contaminated with color and/or "flavor agents" (yes, they actually call it that on the label, yummy) since the target usage is washing clothes.

It's possible that pool shops in your District 12 may carry pure bleach, and possibly in higher volumes and at higher concentrations than the household bleach, which makes using it more convenient.

Be sure to price out all the alternatives (household bleach, pool-shop bleach, and cal hypo) because there could be a huge difference.

Free Chlorine (FC) vs. Total Chlorine (TC)

This will be an important concept when evaluating the chemical test kits you have available:

Good test kits measure both FC and TC. Crappy cheap test kits only measure TC, and they do it badly.

And, yes you guessed it, in District 12 you can likely only find the bad TC-only test kits such as OTO.

Without any way of measuring FC, a lot of the day-to-day maintenance you need to do becomes a lot harder and hit-and-miss, since you are not directly measuring the useful chlorine in the water.

That is, since

Free Chlorine (FC) + Combined Chorine (CC) = Total Chlorine (TC)
Then if you get a certain reading of Total Chlorine (TC) from your OTO test, it's possible that most or all of that chlorine is the useless Combined Chlorine (CC) and none of it is the useful Free Chlorine (FC).

Certain useful pool procedures, like SLAMming the pool (a more refined alternative to shocking a pool that works more reliably) become essentially impossible if you can measure TC but not FC.

We'll talk more below about how you can deal with this harsh reality.

Chlorine Stabilizers

Many pool maintenance guides in District 1, including many of the good DIY guides like Trouble Free Pool, consider it essential to use some level of a chlorine stabilizer.

Chlorine stabilizers come under many names, like "cyanuric acid (CYA)" and "conditioner." Stabilizer often comes combined together with solid chlorine products, such as dichlor and trichlor pucks.

First let's understand what exactly the stabilizer is for:

This video is generally pretty good but has one glaring error: when you use CYA stabilizers in your pool, it does have the advantages described in the video, but the more stabilizer you use, the higher a level of chlorine (specifically Free Chlorine) you need to maintain in your pool. Here's a handy chart. For example, if you have 60ppm of CYA, you need to add more chlorine to keep your Free Chlorine level at 7-9ppm, not the 1-3ppm he mentions in that video.

This is why some people consider stabilizers to be a "trap" or "scam" of sorts. Some products like dichlor/trichlor pucks, which you keep in your pool continuously, will slowly increase CYA level over a season and thus increase the need for chlorine to very high levels. There is no way to get rid of CYA other than draining your pool.

Fortunately or unfortunately, chances are good that you cannot purchase any kind of stabilizer in your District 12 (neither CYA by itself or diclor/trichlor).

You can perhaps consider this a blessing.

Notice how one of the reasons for stabilizer cited above is that it makes the chlorine last longer. But this assumes chlorine is relatively expensive compared to the stabilizer. In District 12, the relative prices can be completely opposite (since stabilizer would be imported and chlorine would be local) so that particular reason may not actually make sense at all.

Some people on the Trouble Free Pool forum say that stabilizer is needed for reasons other than just saving Chlorine. One helpful poster mentioned:

Chlorine is exponentially strong when not buffered/protected by a minimal amount of stabilizer. For indoor pools we recommend about 20 ppm of CYA to take the edge off of the harshness of the chlorine.
His recommendation of 20ppm is much lower than the 30-80ppm recommended by Swim University in the video above, but it's not zero.

I'm not sure what he means by the "harshness." Swimmers in our pool never had a problem with 0 CYA. So perhaps District 12 will be OK without stabilizer.

Test Kits are NOT Made Alike!

So we've discussed which chemicals you'll need and which levels you need to monitor.

To monitor those levels, you're going to need one or more test kits.

You would think that all test kits would just work, with some measuring more kinds of chemicals than others.

Sadly, that is far from the truth.

Get ready for a rude awakening and watch this awesome video (from Trouble Free Pool, which is a crowd-sourced non-profit pool maintenance forum and they are not selling any test kits):

As shown there, the vast majority of test kits available in the world are complete and total garbage. Either they are not precise enough, or they fail to measure critical levels like FC, or they require you to have super-human perception to compare one shade of yellow against an essentially identical shade of yellow for a measurement difference that is critical for your pool, or they are just completely broken and test nothing at all.

In District 1, there is simply no question what to use. There are some $90-108 test kits from Taylor (Taylor TF-100 or Taylor K-2006C), LaMotte (7022), and TFTestKits (TF-100XL) (click the link for a comparison) that are good for many months of pool operation where:

And I'll bet you know where this is going...

That's right! None of these test kits are available in District 12, nor can they be shipped to District 12 at any cost.

Instead, the "state of the art" in District 12 is awful. Everyone, including the "professionals," uses a standard cheap Chinese 2-chemical test kit that is close to worthless:

This kit measures only two things: Total Chlorine (TC) and pH. And it does it badly. Really badly. Notice how the shades of yellow in the OTO chlorine test on the left are essentially identical. Not only would they be impossible for anyone without X-Ray vision to distinguish, but the actual shade you get during a test is nothing like any of the samples! On the right, we have the "standard" phenol red pH test, but again when you do an actual test, the colors you get bear no resemblance to the samples, or if they do (as I verified with a better test) the numbers are completely incorrect. The errors are massive (easily 2.0 pH difference) and this could make the difference between a safe pool and an unsafe pool.

In theory, a test kit like this could work, but the kits in District 12 are manufactured (in China) with negligent, bordering on fraudulent, levels of quality control for an audience who doesn't know they could do better.

It is like a cruel joke perpetrated on an entire sub-continent.

If you ever take your little bottles of OTO and phenol red to be refilled at the local pool shops, you will be even more horrified as you watch the owner use the same plastic pipette to refill both bottles, without cleaning it, thus mixing the two test chemicals in a way that I later determined completely invalidates the results of both tests.

Even more crucially, pool "professionals" in District 12 have never even heard of the good test kits or have ever even thought of why you might want/need a test kit with the good properties above.

That social reality of District 12 should actually be more shocking to you than the poor equipment quality. It's so important that let's even put a big red box around it:

Pool "professionals" here really believe that it is possible to safely maintain a pool using only this test kit.

That is why even if you leave your pool maintenance to a "professional," it is not necessarily safer than if you DIY as a total beginner.

The local "professionals" also wouldn't pay for a $90-108 test kit due to short-term thinking ($100 is equivalent to their service charge for 2 months of service 2 times a week for 1 customer), even though it saves much more money in wasted chlorine and acid over time, but we don't even get to that stage of decision because they don't even know that test kit exists.

You might think that test strips offer an answer. In fact, there are literally hundreds of brands of test strips like the one below, available locally and online in District 12, all at insanely low prices like $2-3 per bottle, and they seem to measure everything we need:

Unfortunately, the test strips available in District 12 are even worse than the "standard" liquid kit above.

I tried to use test strips for several months, ordering 2 different brands, and I finally realized they actually have negative value. The colors that appear never get anywhere near the samples on the bottles, and in cases where I knew certain levels from other reliable sources, I caught the test strips turning essentially random colors from test to test. They are complete and utter garbage.

In District 1, if you pop up Amazon and look at reviews for pool test strips, you will see that 99% of them are worthless as well, but that there are a few brands that some (not all) pool maintainers think actually give useful results. I don't know if that's true or not.

But in District 12, 100% of them are trash.

Making Due in District 12

So it seems we are screwed in District 12. How can we maintain our pool if we cannot even measure its key chemical levels?

Well, to a certain extent, we are screwed. We will never be able to, for example, measure alkalinity with any degree of confidence.

However, like everyone in District 12, we can find some creative ways to get by...

Electronic pH Meter

For pH measurement, after many false starts, I was able to find an electronic pH meter like this available on the local Amazon equivalent (Lazada/Alibaba) for about $3 in a kit like this:

I'm not sure what market it's designed for, but not pool maintenance. This type of meter actually doesn't completely suck.

Out of the box, its measurements were quite inaccurate, but fortunately you can buy it bundled with 2 or 3 pH buffer powders (as shown above) that you can use to calibrate the meter and achieve better than 0.1 pH accuracy, which is over twenty times more accuracy than the crappy phenol red liquid test above and well in the useful range for pool maintenance. Provided you store your meter in a glass of water and don't let its electrode bulb dry out, you only need to calibrate every year or so.

To calibrate the meter though, there's a catch: you need to find de-ionized water (which is not the same as distilled water or anything you will find at any local food or medical shop). That's a bit of a tough call in District 1 and even tougher in District 12. Fortunately, most municipalities in District 12 have at least one person whose job it is to test the local tap water, or to produce drinking water, and these people most likely will have access to de-ionized water. In my case the guy who makes my drinking water knew of a local university of water sanitation, and I was able to score some double de-ionized water for $3.

Here's how to calibrate:

A reasonable question is: should we trust pH buffer powder bought from the same dubious Chinese sources? My chemistry expert friends tell me that pH buffer powders are such a standardized low-tech item that it's actually hard to mess them up, so there is little risk that they will be as bad as the test strips. Plus, unlike the pool test strips, these buffer powders are used to test drinking water all over the world for millions of people, so there is at least some incentive not to screw them up.

Alkalinity Tricks

I was never able to find a real test for alkalinity, but with a lot of experimentation with baking soda I did notice that the alkalinity swatch on one of the two crappy brands of test strips I was using at least behaves in a continuous manner rather than a random manner like most of the other swatches. That is, as I slowly added substances that I knew would raise the alkalinity, the color of the alkalinity swatch would move through the set of colors shown on the bottle, even though the actual number shown underneath each color was obviously completely wrong. So I at least had a way to test if one water had more or less alkalinity than another water. This is imperfect, and not satisfying, but slightly better than nothing.

When I first revived the pool, I took a completely blind guess about the initial alkalinity, and then used online pool calculators to calculate how much chemicals to add to get me to the "right" alkalinity level. I then used the test strip and took note of that color. Then later I could check back if the level had gone down. I can never be sure that the absolute alkalinity was right or not, but at least I can compare the current state against the previous state.

At some point I ran across a description for a method of measuring alkalinity that only requires a pH meter, buffer powders, and deionized water, all of which I had already located as explained above. The core of the method is:

Total alkalinity is measured by collecting a water sample, and measuring the amount of acid needed to bring the sample to a pH of 4.2. At this pH all the alkaline compounds in the sample are "used up."
This seems promising as a DIY method to bypass the worthless test strips. I don't know if this method, which was designed for river and lake water, would also work on pools with higher alkalinity levels. But if anyone tries and has success with this, let us know!

Chlorine Tricks

There are some electronic chlorine meters available on our District 12 local Amazon equivalent (Lazada/Alibaba), but sadly they did not provide a solution like the pH meter did. Most of them measured chlorine levels in giant ranges like 0-100ppm, 100-200ppm, etc. (I cannot imagine what one might use that for?!). And all of them were clearly garbage from the reviews and even from the pictures.

So, my only choice was to try to make due with the OTO Total Chlorine test that I had available (the liquid test that turns yellow, or yellow, or yellow depending on the TC level, and never turns the same yellow as the yellows on the box).

I read here that:

This test measures TC, but if you watch closely it is possible to get a sense of the presence of CC. When you first add the drops of R-0600, the sample will immediately show the FC level. Then, over the next minute or so, it will drift up to the TC level. If you see the color changing, CC is present. Using the test in this way requires careful attention and a good ability to distinguish shades of yellow quickly.
That seemed really promising, but unfortunately I could never get any behavior like that, even with water that I believed contained a lot of Combined Chlorine (the useless byproducts found in dirty water). Perhaps the cheap Chinese OTO formulation is somehow different.

So instead I turned to trying to at least extract accurate relative measurements of TC ppm, similar to the alkalinity.

This turned into a deep but interesting rathole.

Every single day, I tested my pool water with two different OTO test kits (identical design but purchased from two different sources). I took a digital photo of the test kit at night with the same smartphone camera, against the same white wall, at exactly the same zoom and distance and framing, with exactly the same ceiling lights, with the wall lit up by the exact same flashlight at the exact same setting in the exact same position every time. I tried to eliminate all possible sources of variation so that could independently compare the shades of yellow showing up in the OTO vial.

I ended up with a massive collection of 300 photos of OTO results, and kept records of how much chlorine I added before and after each photo, as well as how hot that day was and other factors that would affect the rate of burning off chlorine.

Using this, I was able to build a model of how the subtly different actual shades of yellow (which, of course, were never remotely close to any of the shades of yellow on the test's guide) actually correspond to chlorine levels in ppm. This at least convinced me that the Chinese OTO results were continuous like the alkalinity results were above.

But my eyes were still not good enough to distinguish the shades of yellow even after understanding what the real "spectrum" of shades were.

So then I really fell into the rathole and wrote an Excel spreadsheet and later a C program to analyze all 300 images and find a pattern in the shades. I could then take a new photo for today's chlorine and determine with an extremely high level of accuracy where it falls in the 300 samples.

Again, as with the alkalinity hack above, I never had and still do not have any absolute idea about the chlorine ppm of any particular sample, but I have at least now organized the samples along a continuum.

Then I was able to use hints from outside to make a guess about where certain samples fall. For example, one day I had the chlorine too high and my friend's sensitive skin itched, which it did not on other days (and the pH was not particularly high on that day, so her reaction was probably chlorine-related). I was at least able to mark that point as "too high" even though I did not know (and still do not know) its actual ppm value.

This is a pretty sad solution, but at least I enjoyed myself with the science project. I hope some day to adapt my code into an app that others can use to get highly accurate (albeit relative) measurements from different chemical tests. I don't have any faith that color-based test kits from different vendors will have the same actual colors, but at least one can calibrate using one's chosen brand and use that calibration to quickly measure future samples against older samples.

But the takeaway for the reader is that you can at least learn the relative chlorine levels by carefully watching your OTO results, and possibly photographing them, and keeping in mind how they change in reaction to adding lots or little chlorine. There is some hope that you can at least squeeze some value out of the tests.

That is the essence of living in District 12.

Other Tests

I never sought out a stabilizer/CYA test because there is no CYA available here (another blessing).

I never found a calcium hardness test that yielded any meaningful results, which is a shame because my only chlorine source was cal hypo crystals, so it's quite possible my calcium is dangerously high and may damage my pool plumbing. I see there are already little calcium stalactites in my pool's utility cave from previous years so there might already be long-term damage in the plumbing. My strip test kits both supposedly measure calcium hardness but the actual colors I get are essentially random.

A helpful TFP user points out that the site's pool calculator app PoolMath has a summary function that can estimate the rise in calcium hardness caused by adding a specified amount of cal hypo. So that can at least give a lower bound on the true amount of calcium (but there could have already been a lot of calcium in the water before I revived the pool). Sadly the only way to permanently lower the calcium is to partially or completely drain the pool.

If anyone has insights for a DIY method of measuring calcium hardness or other chemical levels that might work with the limited tools available in District 12, let us know!

Time for Pool School!

Above, we explained some of the most important basics of pool plumbing and pool chemistry, with special notes for lucky people living in District 12.

But we most definitely have not explained everything you'll need to know to maintain your pool. You'll need to learn the steps to shock your pool, learn more about pool cleaning, learn to optimize pool circulation by aiming your return jets, learn about pool covers, learn how to winterize and later open the pool (if applicable), and other important topics.

Your next step should be to head to one of the better websites and/or YouTube channels to learn more:

Contact Us

We hope you've found this useful or at least entertaining.

Please send any comments and questions to

Submit This SiteLike what you see?
Help spread the word on social media:
Support This SiteIf you have enjoyed this site, here are a few ways that you can help me get time to expand it further:
donate now   Donate Now
Use your credit card or PayPal to donate in support of the site.
get anything from
Use this link to Amazon—you pay the same, I get 4%.
get my thai dictionary app
Learn Thai with my Talking Thai-English-Thai Dictionary app: iOS, Android, Windows.
get my thai phrasebook app
Experience Thailand richly with my Talking Thai-English-Thai Phrasebook app.
get my chinese phrasebook app
Visit China easily with my Talking Chinese-English-Chinese Phrasebook app.
get thailand fever
I co-authored this bilingual cultural guide to Thai-Western romantic relationships.
CopyrightAll text and images copyright 1999-2021 Chris Pirazzi unless otherwise indicated.
Submit This Site

Like what you see?
Help spread the word on social media:
Support This Site

If you have enjoyed this site, here are a few ways that you can help me get time to expand it further:
donate now   Donate Now
Use your credit card or PayPal to donate in support of the site.
get anything from
Use this link to Amazon—you pay the same, I get 4%.
get my thai dictionary app
Learn Thai with my Talking Thai-English-Thai Dictionary app: iOS, Android, Windows.
get my thai phrasebook app
Experience Thailand richly with my Talking Thai-English-Thai Phrasebook app.
get my chinese phrasebook app
Visit China easily with my Talking Chinese-English-Chinese Phrasebook app.
get thailand fever
I co-authored this bilingual cultural guide to Thai-Western romantic relationships.

All text and images copyright 1999-2021 Chris Pirazzi unless otherwise indicated.