Eric challenges "pH dogma" by showing that pH does NOT control chlorine strength when cyanuric acid (CYA) is in the water. The free chlorine to cyanuric acid ratio (FC:CYA) determines chlorine strength.
00:00 - An extra-long intro, complete with Jarred's new microphone and some housekeeping topics.
01:24 - Housekeeping: We're teaching with Watershapes University. WU C3611, November 12 and 13 in Las Vegas: Essential Plaster Workshop. And we're participating in Swim Across America, September 24 in Dallas. You can contribute to our team at swimacrossamerica.org/goto/orenda.
03:38 - Check out the chlorine and CYA chart here: https://blog.orendatech.com/chlorine-ph-and-cya-relationships
04:55 - When you introduce CYA into the water, pH no longer controls the strength of chlorine (%HOCl)!!
08:23 - Chlorine strength is determined by the FC:CYA ratio. It's only a matter of time until health departments recognize this.
10:58 - At a high enough pH, OCl- will break away from CYA and can be destroyed by sunlight. Focus on your pH ceiling to avoid this fate.
13:50 - Simplifying the complex
15:36 - The Orenda program takes these overlapping factors into account, so you do not need to understand all of the chemistry. We've taken things into consideration for you. Just follow the plan and the chemistry will behave.
18:05 - Paradigm shifts are never comfortable
18:42 - Summary. Thanks for listening!
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79. CYA, pH and Chlorine Strength
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[00:00:00] Eric Knight: I have a question. Have you ever been taught something in life that you believed to be true? And it has always been true in your mind? You just don't doubt it, right? It's just, it is what it is. Two plus two is four, something like that. And you just know that that is not arguable, we accept it as fact, we move on. And then later in your life, you find out that that whole thing was wrong.
[00:00:29] The paradigm is broken. And all that time, you were believing something that you believed to be true, but it wasn't. It's not an easy thing to comprehend. And that is actually the subject of today's episode. This is episode 79 of the Rule Your Pool podcast. I'm your host, Eric Knight doing this one alone.
[00:00:52] That's why I said host, not co-host. Jarred is not on this. And there's a high likelihood that Jarred's not even going to listen to this so we can talk about him behind his back. In today's episode, I'm going to talk to you about how cyanuric acid affects chlorine's strength. Specifically, I'm going to address the dogma, perhaps the myth that pH always controls the strength of chlorine. So let's get right into it.
Housekeeping
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[00:01:24] Eric Knight: As a quick reminder, we have two housekeeping items. We are teaching with Watershapes University this November 12th and 13th, before the international show in Las Vegas. That class number is WU C3611, essential plaster workshop. We have a small part in that class. It's not our class, it's a Watershapes University class, but we will be teaching the water chemistry portion of it. And we're very excited for it. There's only 60 seats. So if you are in the trade and you want to take that class, book it now before it's sold out.
[00:02:17] And the other item: Swim Across America. September 24th, we are swimming across a lake in Dallas to honor our employee Kelly. We lost her to cancer this year. Um, it was just tragic. And so we are going to participate in a charity, and that charity is Swim Across America.
[00:02:34] They invest money in experimental treatments with pretty high degrees of success. I don't know if you heard about it in the news. We talked about this a couple episodes ago, that there was a cancer treatment done with a hundred percent remission in the clinical studies. That's never been done before. And the first people who funded that study was Swim Across America.
[00:02:57] So we don't make a penny on it, but if you want to support our team, all of the proceeds go to Swim Across America. It is all tax deductable, and it can be anonymous. There's no pressure. We won't know if you did, unless you want to put your name on it and tell us who to swim for. We will write their names on our back, and if we raise enough money, Jarred is going to swim too. That event is going to be September 24th in Dallas and our team page, if you would like to contribute is swimacrossamerica.org/goto/orenda. That's swimacrossamerica.org/goto/orenda. We will put the link below.
%HOCl
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[00:03:38] Eric Knight: Okay. There is a chart in the Orenda blog. You can find it going to blog.orendatech.com, or if you have the app go to the main menu, blog, and you're just going to search CYA. And you're going to find an article, Chlorine pH and cyanuric acid relationships. That's what you're looking for. And there's a graphic in there, two charts next to each other. And that's what we're going to talk about. For those of you listening on YouTube, just because I'm not being recorded on video, we will put this up on the screen right now.
pH, chlorine and CYA chart
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[00:04:10] Eric Knight: Magic. Take a look at that chart. If you're listening to this while you're driving, uh, just check it out after the episode, it'll make a lot more sense, but that's what we're going to talk about. All right. Here's the premise of this episode. Everybody seems to believe and has always believed that the pH controls the strength of your chlorine.
[00:04:32] And that's true if there's no cyanuric acid present. And this is what I would refer to as pH dogma. Everyone has been chasing pH to keep it low because they want strong chlorine, because that is what we have always been taught. That's what we've always believed. And how dare you question it? It just is what it is.
[00:04:55] But the truth is when you introduce cyanuric acid to this equation, you put CYA in your water, which is like most outdoor pools in America, for sure, that chemistry goes out the window. It's totally different. Look at the graph. The chart we're all used to is on the left, and you can see that the lower your pH, the stronger the percentage.
[00:05:19] Let me back up. When you put any chlorine in the water, any type of chlorine, when Cl, chlorine Cl2 goes into the water and it dissolves, it interacts with water, H2O, you get two different species. You get hypochlorous acid, HOCl, which is the strong, powerful, killing form of chlorine.
[00:05:39] And then you get the hypochlorite ion, OCl-. That is over a hundred times weaker, slower. It's the yin and yang of chlorine. And they are in equilibrium. The pH determines that equilibrium. That's what that chart shows you. So the lower the pH, the hydrogen stays on that's why it's H OCL and then the higher, the pH the hydrogen leaves. And you get OCL with a minus, which is where that hydrogen jumped off.
[00:06:07] So that's the two types of chlorine. And this is the chart that we've always used. But look at the chart on the right now, and compare it to the chart on the left. The only difference between these two charts is 30 parts per million of CYA.
[00:06:21] And wow, what a difference! Where is the red line now?
[00:06:28] Oh yeah, it's at the floor. At just 30 parts per million, between, you know, the pH of 7.0 and 8.5, you're less than 3% hypochlorous acid. Contrast that with the other chart. If you're at, say a 7.4 pH on the other chart, that's looking like, Hmm. I don't know. Almost 60% hypochlorous acid. You're telling me that that's now less than 3%? Well, yeah, actually. But that's not all bad news because if you look up at the top, there's a new line that was not present in the other one. It's that purple line that says Cl-CYA, and this is chlorine bound to CYA.
[00:07:09] And so what this is telling us is at just 30 ppm CYA, approximately 97% of your chlorine is protected from sunlight because it's bound to CYA. 97%! Which means the other 3% or less is going to be the hypochlorous acid. That's the red line at the bottom.
[00:07:31] Circle back into our fourth pillar of proactive pool care. Minimal CYA. You don't need a lot. Orenda recommends below 50. 30 to 50 is pretty optimal for residential pools. You could be lower than 30 on a commercial pool, especially if you have a chlorine feeder, you don't need over 30. You get a lot more sunlight protection than you might think.
[00:07:52] So what is this telling us? Well, if you look at it, there's not really that big of a difference between 7.0, 7.5, 8.0 and 8.5 on the red line. It's pretty flat. It's all below 3%. So there's not really a difference in chlorine strength as we're used to referring to it. Because chlorine strength has always been the percentage of hypochlorous acid. Well, that's the red line. And now it's flat at the bottom of the screen. So you have to look at it in a different context.
Chlorine strength, with CYA in the water, is no longer %HOCl. It's the FC:CYA ratio.
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[00:08:23] Eric Knight: The strength of chlorine is actually the ratio of free chlorine to cyanuric acid. That is what you need to be paying attention to. And before you commercial operators go, whoa, well the health department still care about pH.
[00:08:38] Yes, they do. For now. And they probably will for many years because health codes change at the pace of government. And we all know that that takes a long time.
Contact Time (CT)
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[00:08:47] Eric Knight: If you look at the article, you'll see a chart that comes from the CDC. And it shows something called contact time for various germs, like E coli, Giardia, uh, this virus, that virus. Contact time is what health departments care about. How much time does a germ in contact with chlorine take to be killed?
[00:09:11] So the contact time, the CT value, is very important. And that's why commercial codes have this pH requirement that you cannot go over, in most cases, 7.8 pH. They're caring about contact time. Now, contact time is more profoundly going to be impacted by the free chlorine to cyanuric acid ratio than pH.
[00:09:34] Now an indoor pool, yeah, pH controls it because there's no CYA. But contact time is always relevant.
[00:09:41] There's a lot of research that shows what the free chlorine to cyanuric acid ratio does to contact time. And it is my belief that in the future, the health codes will be adapted to show the free chlorine to CYA relationship instead of just pH. I think that's where it's going. I hope that's where it's going. Because that's what really matters.
[00:10:01] It's impractical to try to force pH somewhere. When what really matters is something else.
pH Dogma
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[00:10:06] Eric Knight: But the reason that they have a pH threshold, like most of them I think is 7.8 or less, is because of this old dogma. Which is why I'm doing this episode in the first place.
[00:10:18] Everyone has believed this forever. And I'm not here to say that they're all wrong. It's that they didn't have all the information when those codes were written. Now there is. The research exists. It's been presented to the model aquatic health code. I'm not making it up. Look it up. We cite this all over our website. You could read it yourself.
[00:10:38] It's very obvious that the free chlorine to cyanuric acid ratio is what is determining the strength of your chlorine. Now pH will impact it a little bit, but I would argue it's negligible. That's my opinion. But pH will start to matter as the pH gets over, I don't know, 8.0, 8.1, 8.2 ish.
[00:10:58] If you look at the chart, it starts curving up at the bottom and the purple line at the top starts curving down. And what that means is at that point, you start having hypochlorite ion (OCl-) break away from cyanuric acid, and it could get fried by the sun. A couple episodes ago, Jarred and I were talking about using chlorine versus losing chlorine.
OCl- leaving CYA is different from losing chlorine strength
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[00:11:25] Eric Knight: And in this circumstance, if your pH gets too high, then you will be losing chlorine to sunlight because it's breaking away from its protection. That has nothing to do with chlorine's strength. That has everything to do with its binding to CYA and releasing from CYA. Two different things.
[00:11:44] But the point I'm trying to make here is, if you still are chasing pH every day because you are trying to make sure your chlorine is more effective, I've got news for you. Look at the chart. You could lower your pH down to 7.0, and you're not going to make that big of a difference... I would argue a negligible difference in chlorine strength. What you really should be managing is your cyanuric acid level.
[00:12:11] And this ties into what we talk about. Think of all the other episodes we've done. We've talked about standardizing your pool chemistry. What's the first step? Well, you test your water and you dilute to get your CYA where it needs to be. If dilution is necessary there. You might already be there. But you always start with your CYA.
[00:12:29] Why? Because it impacts just about everything. And in order to get it down, you have to dilute or use reverse osmosis filtration. At least now. Technology just isn't there to successfully remove it easily. If it existed, trust me, we would know about it. And we would talk about it. CYA is, is a real problem in these pools.
[00:12:49] High CYA, a little bit of CYA is great. Too much causes over stabilization, and that's a really bad thing. Cyanuric acid doesn't just impact your chlorination. It impacts your LSI. It impacts your carbonate alkalinity. It impacts your pH ceiling. It just impacts everything. Kind of like pH impacts everything. Everything's kind of interrelated. There's a lot of crosspollination.
[00:13:16] If this is starting to sound familiar, that's a good thing because we talk about this at Orenda a lot. Our philosophy is to look at the holistic balance of water, not focusing on one discipline.
[00:13:28] Oh, chlorine. We're focusing on chlorination. Oh, we're focusing on calcium hardness or alkalinity levels. No, that's not how we teach. We teach the LSI. We teach Henry's law. We teach containing pH. We do these things for a reason because all of them are interrelated.
Simplifying the complex
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[00:13:50] Eric Knight: And I realize this is all very complex. Try doing the research, reading the white papers and distilling it all down and making sense of it in your head, and then applying it, then publishing it, then talking about it on a podcast.
[00:14:01] Trust me, we are trying to make this as applicable to you as possible so that you don't have to do the research. That's the point of this podcast. We want you to be able to Rule Your Pool and not have to think about it too much.
[00:14:15] So let's follow a plan that actually takes in all of these other things that you're not going to think about, most of us won't anyway, so that they're just taken into account. They're taken care of. Don't worry about it.
[00:14:27] That's what the four pillars are about. You know, LSI balance year round. You don't have to understand the LSI, just use the calculator. Keep the numbers green and yellow. Predict the temperature is getting colder. That kind of thing. You don't have to understand what it means. Just follow it and the water will behave in your favor.
[00:14:45] Supplement chlorine. You don't have to know why. We teach you why, but you don't have to know it. Keep your phosphates low. You don't have to understand why. But if you do it's to your advantage. And then of course, pillar four, keep your CYA 50 or less. There's a lot of reasons to keep your CYA minimal.
[00:15:02] You want some. Some is great. Too much is bad. So we just say 50 or less. Simplify it. Don't go over 50. And if you do, it's a two edge sword, you could do that intentionally and slow down your chlorine so that you can hold it for a week, but you are deliberately slowing down your chlorine.
[00:15:25] So be thinking about that and supplement your chlorine. Act accordingly. Protect against the downside. That's all I'm trying to say.
Follow the program that takes these factors into account for you
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[00:15:36] Eric Knight: So to summarize this, we need to get out of the mindset of thinking that pH alone is controlling the strength of our chlorine. Because when cyanuric acid is in there, a wrench is thrown into that equation. It is not the same chemistry.
[00:15:49] Look at the chart. Look at our references, we cite it. Read the research for yourself. If the pH gets high enough. Chlorine will break away from CYA and get burned out by the sun. So you don't want the pH to get high enough, which is why, spinning back into something else we teach, you want to focus on your pH ceiling. Your carbonate alkalinity that drives your pH ceiling.
[00:16:16] All of this is available in the app now. It shows your pH ceiling in real time. We did that on purpose. So, if you have a responsible amount of CYA, you have enough calcium hardness to allow you to have a lower total alkalinity.
[00:16:30] Your pH ceiling is going to be limited, which means your pH is not going to get so high that you lose a lot of chlorine to the sun. Listen, a few episodes ago when we, uh, Jarred and I were talking about chlorine, not lasting a week. Listen to that episode again. We talked about using versus losing.
[00:16:48] Don't let your pH get that high. Well, the best way to do that. Is to limit how high the pH can go and then break your bad habits of pouring acid straight into a pool. Dilute it. Measure it. So that you're not etching the pool and forcing the pH to go too high. We see it all the time. These are the practices that you can put into place to Rule Your Pool so that you don't have to understand everything that's going on.
[00:17:14] Just understand that whether you like it or not, CYA is going to do what it does. pH is going to act the way that it does. All this chemistry, to some degree, is out of your control. All you can do is manipulate chemistry with chemicals. You can't control what it's going to do. But by following a program that takes it into account, you can put your water in a position that its next move is predictable and where you want it to be.
[00:17:43] That's what we're all about. if you want to go back and put more context to this conversation, you can read the blog. It's called chlorine pH and cyanuric acid relationships. You can go back and listen to these other episodes. Episode 8, 24, 30, 47, 59 and 70.
Paradigm shifts are never comfortable
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[00:18:05] Eric Knight: In closing, I realize it's uncomfortable when a paradigm has shifted. If you've believed something for so long, that it is true, right? It's gotta be true. It's always been true. I'm not saying that what we believed about pH controlling the strength of chlorine was wrong. Because it wasn't in non-CYA pools. It's still true.
[00:18:27] We just weren't taught the other part of this equation. We weren't taught the impact that cyanuric acid actually has on chlorination. It's massive. And I hope this episode helps clarify that for you.
[00:18:42] This is episode 79 of the Rule Your Pool podcast. I'm your host Eric Knight. I appreciate your time so much. And your comments, and your questions to podcast@orendatech.com, that's the email. You got questions? Email me: podcast@orendatech.com. We've been getting so much feedback on our help center, ask.orendatech.com.
[00:19:03] Great ideas for episodes, and because of some of the topics that you have suggested and asked for, in the next few episodes, we're going to have some experts on here that are not with Orenda.
[00:19:13] They are subject matter experts. Gurus. And we're going to ask them some of the questions that you have asked us. So thank you for listening. If you find this episode valuable, please share it with your friends, share it with people who might need to hear it, and you don't need to take my word for it. Trust but verify. All the research is out there on your own.
[00:19:30] Until next time. Take care and enjoy ruling your pool.