Eric takes a question from a customer who emailed in, regarding disappearing CYA and chlorine in a covered pool. The suspicion is that some sort of bacteria could be breaking down CYA, and indeed, that is plausible. If that's the case, Eric discusses what to do.
[00:00] - Intro
[02:51] - Research on Nitrogen Compounds in Water
[07:02] - Bacteria vs. Nitrogen Compounds
[10:36] - Case Study: Covered Pool in Southern California
[14:36] - What can be done?
[20:48] - Closing
202. Bacterial Breakdown of CYA
===
Eric Knight: Welcome back to the Rule Your Pool podcast. I'm your host, Eric Knight. This is episode 202, and we're going back old school on this one. And what I mean by old school is this topic came in from a listener and a customer of ours who wrote into the email, and you can do the same if you have good questions for the show. It's ruleyourpool@gmail.com.
And I want to thank this customer for doing this because this one got me to scratch my head. A lot of the answers I could just simply respond in email. This one I'm like, "Ooh, ooh, that's going to take some homework. I like this." And it kind of wraps up cyanuric acid and breakpoint chlorination and ammonia and chloramines and all sorts of stuff that we love talking about.
So I went into my cabinet and I got my old classic PR 10,000 Orenda hat, and I'm going to put that Orenda hat on. Obviously, I'm with Pool Brain now, but the reason I'm putting this hat on is because this reminds me of the kind of research I was doing when I was still writing blogs and doing this podcast behind the microphone as Orenda.
This is right up our alley, and I wish I had been asked this question many years ago. But at the same time, now with the power of AI to help find the research so much faster, I still read all of it, but it can identify a lot of things a lot faster. And so I was able to do this research in a fraction of the time that it probably would have taken back then.
So let me just ask the question and then we'll get into this episode. So here's the question. It's from Aqua Docs Pool Service. Thank you for writing this. And they said, "Hey, Eric, do you have any write-ups or episodes about cyanuric acid bacteria that causes ammonia in the water and how to treat it?
My brother-in-law has a pool here in Southern California that he is having issues with. It's a plaster pool, and it's covered, and it's covered all the time unless it's being used. The pH drops down to 7.0 to 7.2 on its own. Last week it was 7.6, but today it's 7.0. Total alkalinity is 180. CYA is basically zero, maybe a five, and that's with adding eight pounds of conditioner.
Still zero. Customer added one gallon of liquid conditioner and that seemed to hold for a while, but two weeks later it was back to zero. So this pool is not holding conditioner. There are no leaks that they know of.
They don't have to add water like crazy or anything like that. It's been hot here constantly for the last couple of months, and that pool being covered means the water is pretty hot. I'm trying to figure out why it won't hold conditioner, and we are leaning towards a cyanuric bacteria that's possibly eating away at it.
Could you provide any insights on this if you don't mind? Wish we could have a phone conversation because we're kind of stumped. Anyway, thanks for always providing advice. We appreciate what you do."
Hey, thank you for writing into the show. This is a great topic, so we are going to talk about, uh, disappearing conditioner.
What could cause that on a covered pool in a hot climate? Especially when you're chlorinating as regularly as you are on your... I guess this is your brother-in-law's pool. So let's get into it, episode 202.
[00:02:51] Research on Nitrogen Compounds in Water
---
Eric Knight: I should start out by saying I still haven't called the person because they didn't leave a phone number for me, and it just says AquaDocs. So I actually don't have a contact number. But I did respond via email, and I said, um, "I don't actually know the answer to that, but I'm going to look into it." I said, "That's a great idea for an episode.
Let me do some research." Well, I have now done that research, and I'm excited to share it with you.
So let's start with the first topic. They're not able to hold cyanuric acid, at least that's what they're bringing up here, and the chlorine is going to zero as well.
Now, to me, the bigger problem is you're not holding chlorine, especially in a covered pool, and perhaps not having CYA is part of that, except that most of the time this pool is covered. So it's not like a sunlight breakdown, but it could be maybe temperature related or something like that. So let's dig a little bit deeper in here.
What could cause CYA that they know for a fact they added, both in granular form and in liquid form, according to the email, and yet nothing? Well, the first thing that comes to mind is what if it's a distorted test? Maybe there's something wrong with the reagent. Maybe the melamine isn't reacting or something like that.
And, and anybody listening to this show who's been testing water knows tests are not always 100% accurate. Um, they usually are, at least we, we hope so. But things can go wrong. Maybe there's some interfering factor that we're not thinking about. But for the purpose of this episode, let's just assume that it is an accurate test, and they're just not reading CYA because CYA is going somewhere.
What could cause that? Well, the first answer to that is CYA is a nitrogen compound. And if we want to understand nitrogen compounds, the main source that I've used over the past few years, you can look it up yourself. Is John Wojtowicz's article, which is in the Journal of the Swimming Pool and Spa Industry, JSPSI. You can find this on poolhelp.com. It's also linked to on the Orenda website as well. And the article was written in 2001, volume 4, number 1, pages 30 to 40, and it is called Chemistry of Nitrogen Compounds in Swimming Pool Water by John Wojtowicz.
Now, in here it goes pretty deep chemistry, and it talks about the various types of nitrogen compounds that can get into a swimming pool. And it starts by talking about things that people introduce, mainly urea and creatinine. This is stuff that's in your urine and in your sweat. And it goes through the chemistry required to actually break it down.
And what happens is when these breakdowns happen, they consume a certain amount of chlorine, and they create a pretty defined layer of byproducts. And rule of thumb here, the more complicated the compound that chlorine has to break down, the more byproducts and the more chlorine it's going to take.
That's common sense, right? If it's just simple ammonia, you're going to break that down using breakpoint chlorination. You're going to use a defined amount of chlorine. And, I mean, I think it's a pretty sizable amount of chlorine.
But when you start getting into organic nitrogen compounds like urea, or in this case cyanuric acid, the complexity goes way up. There's a lot more letters in the formula, so to speak, and I'm not going to dwell on all of that, but you can read the article on your own time. But the main thing that you need to realize is what chlorine is doing is only within its own toolbox of what it can do.
Chlorine can oxidize and it can do substitution reactions. It is really hard for chlorine to break a carbon bond. It's just not very good at that, especially in the levels that we're using in swimming pools.
Now, if you had a huge concentration of chlorine that was unsafe for swimming pools? Yeah, it can do it. But we're not doing that, right? Even if you shock the pool, it's not enough to really break that carbon bond.
So he goes through, and, and that's Wojtowicz I'm talking about. He goes through the oxidation of nitrogen compounds by chlorine, breakpoint chlorination of ammonia. He goes through all these formulas, and what we glean from this is it takes a lot of chlorine to get rid of some of these compounds.
[00:07:02] Bacteria vs. Nitrogen Compounds
---
Eric Knight: Now, Let's go back to this. The question then becomes, okay, if chlorine can break down nitrogen compounds, to some degree it can, why doesn't it break down cyanuric acid immediately?
Right? I mean, we're-- even if we shock the pool, we have CYA. We don't see our CYA go down very often. And the reason for that is they actually have an affinity for each other in terms of becoming an isocyanurate. So chlorine is not actually trying to break it down in that form. What actually breaks down cyanuric acid is a little bit different. You need a bacteria. And that bacteria, we're just going to simplify this, and we're going to call it a nitrifying bacteria. The way I learned this many years ago is most of the air that we breathe is N2, nitrogen.
It's nitrogen gas. We breathe it in. Roughly 80% of that is nitrogen in the ambient air around us. About 18 or 19% of that is oxygen, and the rest is everything else, including carbon dioxide. So CO2 is a very small amount. Well The thing is nitrogen gas, N2, is a pretty strong nitrogen bond, and not a lot of things can break it.
Lightning can, and then there's these nitrifying bacteria. And in my class when I talk about water returning to its natural state, part of that is the ecosystem of our earth requires breaking that nitrogen bond specifically in soil. And the way you do that is certain types of bacteria, certain types of, um, I don't think it's, it's specifically algae like what you would find in a pool, but certain types of bacteria that you would have in wet soil in particular, they can break that down.
For instance, legumes like, uh, certain types of peas and peanuts and things like that that grow in the soil, those species have the ability to break down nitrogen into a more usable form that can be absorbed by other plants. So it's super important if you notice, um, how nature is, it's not monoculture like humans have done.
You know, nature doesn't have massive fields of just corn or just fescue grass or just one type of tree. No, it's always this smorgasbord of like a bunch of different plants, and the reason for that is different plants process nitrogen differently. They need different nutrients. They also shed different nutrients, and so it's a symbiotic relationship all throughout nature.
This happens in water. It happens in soil, everywhere, right? So these nitrifying bacteria are super important to break down certain types of nitrogen bond. Again, this is an oversimplification. I'm just trying to make the point here that if you had a type of bacteria that did this, uh, according to this, it's a type of Pseudomonas.
I hope I'm saying that, yeah, Pseudomonas species, uh, and anaerobes. I'm not a biochemist. Maybe I need Dr. Vore on here again to tell me what those are. But apparently, there are certain types of those that can break that nitrogen bond. Now, if you have heard of cyanuric acid remover products, some of those, um, one in particular in my mind is a type of nitrifying bacteria, and the instructions on it say you have to dechlorinate your pool for this to work, and it has to be the right temperature and all these other things.
And the reason for that is chlorine easily kills this type of bacteria. So if you had chlorine, this bacteria dies, and you know, it, it doesn't do its job to break down CYA. But if you dechlorinate it and you give it time at the right temperature and the right conditions, it can start to break down CYA.
[00:10:36] Case Study: Covered Pool in Southern California
---
Eric Knight: So in this case, the question that we're getting here is we have a covered pool. It's covered most of the time. I get the impression it's probably 90% of the time it's covered. It's in Southern California. Gets a lot of sunshine. It's hot. Underneath that cover that's not getting opened much, that water's getting warm, and in the darkness, that's a really nice place for bacteria to grow and reproduce.
Even though it's getting chlorinated every week, for some reason, the chlorine is dropping to zero very, very quickly, and the CYA is also going away. So in my mind, the first thing that comes to mind is there probably is a bacteria in there that is effectively breaking down that, um, cyanuric acid.
But what does it become? So I did some homework here, and when you break down CYA, uh, let's see here. Yes.
When these bacteria break down CYA, one of the byproducts is ammonia, and another one is carbon dioxide. Well, as we know, carbon dioxide likes to off-gas, and if you have a covered pool, it doesn't. So if it doesn't off-gas, it gets redissolved, or at least a portion of it will, which drives the pH down further.
This is why they said in their email, I think, uh, part of the reason why they noticed that their pH goes down each week. Like sometimes it's 7.6, sometimes it's 7.0, and they're not having to add acid to it. Well, it's probably because that CO2 could be coming out of the CYA that is breaking down, theoretically.
Let's find out. So let's play through the scenario. You add CYA, whether it's granular or liquid. It goes in, everything's fine. You could even chlorinate at that time. And in this case, they cover the pool shortly after because they're not using it, and it gets really, really hot. Well, if that bacteria was in the pool and it can break down that CYA and you don't have enough chlorine, for instance, if it's breaking down that CYA, it's converting it into ammonia, which takes a lot of chlorine to break down and, and CO2 separately, right?
That's going to drive the pH down. But what I'm getting at is if you have that happening, especially if the CYA is near zero, driving the pH down is going to increase HOCl, right? Because in a non-stabilized pool, pH directly controls the strength of chlorine because the hydrogen is going to stay bound to the HOCl, which is the active killing form of chlorine, which means it's turbocharged.
It's going to oxidize more stuff. Well, it's going to go after these nitrogen compounds. And so right here, uh, the CYA seems to, you know, air quotes, "vanish" within a week, certainly. And, and it probably happens over the course of a couple of days. So if you have this, the bacteria in there are going to consume CYA because it's food.
Bacteria need to feed on these nitrogen compounds, at least this type of bacteria that might be involved, and it sounds like it is. The pH keeps crashing because this massive buildup of ammonia then undergoes breakpoint chlorination, and that reaction is two ammonia plus three hypochlorous acid becomes nitrogen gas, five hydrogen protons, and three water molecules. Well, five hydrogens drops the pH, right? Hydrogen protons are acids, right? If HOCl splits, you got Van Gogh over here, that's the base, and that hydrogen, Van Gogh's ear, is the acid, so it drops the pH.
Again, this continues to drive the pH down because it's covered. If it was not covered, the pH would rise quite quickly because you have 180 alkalinity in this pool. So there's plenty of carbonate. Henry's Law is going to take over. But you're covering it. You're capping the beer. So it doesn't have the ability to off-gas, therefore the pH is suppressed.
And with the CYA so low, you got pretty active chlorine in that case. That chlorine is going to get used up very, very quickly. And it's going to be used up attacking this nitrogen. Specifically ammonia. And those byproducts continue to... It, it becomes a vicious cycle is I guess what I'm getting at.
[00:14:36] What can be done?
---
Eric Knight: Now, before talking about what we can do about this, let's talk about how we got here. The pool is covered, high alkalinity, yet the pH keeps being pushed down, which should tell you something right there, and it just seems to not be able to hold chlorine or cyanuric acid.
It is most likely a bacteria, nitrifying bacteria getting in there. You know, that's the assumption we're having to make for all of this. The question is, where did it come from? Could be coming from soil. It could be coming from certain fertilizers. It could be coming from, you know, uh, city water.
I don't know. It, it could be coming from the environment. But anyway, if it's in there, and it's thriving, because this bacteria does not do well in direct sunlight, so if it's covered most of the time, it's probably in the pipes. It could be in a biofilm. I don't know. It could be in the filter. I have no idea.
But if it's in there, then indeed it will start to break down CYA. Chlorine is then going to get used up going after the ammonia, which releases byproducts like hydrogen, which will continue to drive the pH down. And since there's almost no CYA, most of that chlorine is going to be in HOCl form, which is the active killing form, which is going to more rapidly get used up, which is why you get the appearance of chlorine vanishing.
Again, all of this is contingent on the assumption here, based on what I'm being told, that there might be this bacteria in the water. If there wasn't this bacteria in the water, I don't think any of this would be happening, so I think it's the most likely thing. But here's how we can find out.
The first thing you can do is you can test for combined chlorine. If there is a high combined chlorine, right off the bat you know that there's a source of nitrogen. Is it coming from CYA? I don't know. CYA is going somewhere, and if CYA is indeed breaking down, then that is likely a case. But you can do some homework, and you can try to find any other sources of nitrogen.
Find out what might be getting into that pool. Test your tap water. Is it chloraminated? And if so, how much? You know, the chloramines here at my house in Charlotte, and I just got a carbon filter to stop it, was 0.25 parts per million. That's a lot. I don't want that in my drinking water. Well, you may have the same thing wherever you live.
But in something like this, I would imagine the number would probably be over a full part per million, um, probably even higher than that. Just because this pool is not breathing, you don't get sunshine, you don't get off-gassing. And if you're off-gassing chloramines, you know, they're, they're out in trichloramine form. Trust me, I know this. I've spent a lot of time with indoor pools and air quality.
But what if your pool is capped? If it's covered like 90% of the time, where's it going to go? Well, it's not. It's going to stay in the water, and then there's other byproducts that can happen.
So, to your question, if you find yourself in this, listeners, in any situation like this, the first thing is test for combined chlorine in both the tap water and the pool.
Number two, instruct the homeowner, or maybe you are the homeowner, leave your pool open for two or three weeks. Let it breathe. Aerate it. Let it do its thing. Let it find its natural state apart from turning green or anything like that. You're still going to chlorinate and all that stuff. But let the CO2 get out.
Let it equalize. Get that alkalinity in line so that you're not driving the pH to, I don't know what the ceiling would be, probably 8.4, 8.5, then you got scale and other things. But what I'm saying is find homeostasis. Let your water relax a little bit, and you will learn a lot more. Because right now there's a lot of forces competing, pushing the pH down, driving the pH up, trying to kill this, creating byproduct that, which consumes more chlorine, which creates another byproduct. There's a lot of confusion in there.
And if you can find that chlorine will hold after you do this, then you know that it's a pretty good start. So what I would do Is I would, again, open the pool. I would test for all these things. I would super chlorinate and leave the pool open, and I would do it in the afternoon when the sun is not directly on the water.
So once the sun is setting, get as much time as you can with no direct sunlight, because your CYA is almost nothing. Shock it. Get that chlorine level up. Now, if you are a pool pro or you have a pool pro, ask them. This might be a good case for non-chlorine shock, like potassium monopersulfate. That is not a cure-all, but it could help in this situation break down some of that nitrogen as well.
You could also, if somebody has a mobile ozone unit, some people put these on carts. They can pull it in the backyard, run it for twenty-four hours. Ozone would destroy this. Ozone would be extremely good for this. Uh, but again, not a lot of pool pros have access to that. Uh, but if they do, that's definitely something that could be done.
You could also call someone like Matt, who was on the podcast several episodes ago, for reverse osmosis filtration. You could get a lot of these nitrogen compounds out that way, specifically if they've been oxidized down to nitrates, because there's really no other way to get nitrates out other than physically draining and replacing water, except RO.
So you could do that. Um, but to verify, just see if you're getting your combined chlorine down. If you are effectively getting that down you know you're also killing that bacteria too. The reason why is because the number would come back up if you were adding CYA and then boom, here we are again, we have more combined chlorine. What we want to do is we want to be able to kill.
The most likely culprit for bacteria to survive are in dark places in the pool that direct sunlight does not hit. Obviously, if the pool is covered most of the time, that's the whole pool. But it's not covered all the time. It's usually going to be in the filter. I would start there. I would purge the filter. I would clean it thoroughly, as thoroughly as you can. If there's any slime in there, that could be a biofilm that's harboring this bacteria. We don't know. But you're going to physically try to clean out as much as you possibly can.
It may require purging the pool with more than just chlorine. I'm incredibly biased. I am wearing my Orenda hat, but you can do an enzyme purge, anything organic in that pool that you could at least loosen up or start breaking down is less organics that chlorine has to get used up trying to fight.
You want chlorine finding bacteria, and you want enough chlorine to make sure it can kill that bacteria effectively. Uh, and then, you know, once the breakpoint chlorination process happens, you got plenty of chlorine demand to begin with. So anything you could do to supplement that, to break that down is going to be a good thing.
[00:20:48] Closing
---
Eric Knight: So that would be my advice. I greatly appreciate the question. Uh, I hope this word salad makes some sense. I think a lot of this is most likely caused by the fact the pool is covered all the time. Let it breathe. Let the air and the sun do its thing and see if that water can calm down and find out where it wants to be.
Then align it that way, and then you can take corrective action. If you have any questions or you have a mystery chemistry issue like this that you would like discussed on the show, again, the email is ruleyourpool@gmail.com. I'm your host, Eric Knight. It has been a pleasure with another episode of this podcast.
So thank you for listening. Tell your friends, and we'll see you in the next one. Thanks.