Warmer weather means chlorine does not last as long in the pool. But is it because more chlorine is lost to sunlight? Do you need more CYA? Or is something else at play? Eric and Jarred dive in deep on the truth about Cyanuric Acid and where chlorine is really going.
00:00 - Intro
01:03 - There's a difference between using chlorine and losing chlorine
02:11 - Chlorinate and cross your fingers
03:59 - Does warmer weather really mean you need more CYA to protect chlorine from more intense sunlight?
08:49 - CYA's other impacts
09:43 - High pH actually does increase chlorine loss, because OCl- dissociates from CYA in higher pH water
12:07 - Jarred did not read all five bullet points in our extensive show notes
13:53 - Low-energy Jarred summarizes for the fans
14:32 - Summary - Thanks for listening! And check out our brand new Help Center: ask.orendatech.com
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70. CYA, Water Temperature, and Chlorine Loss
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[00:00:00] Eric Knight: Welcome back everybody to the Rule Your Pool Podcast. This is episode number 70. Kind of hard to believe. And with me again, two times in a row, Jarred Morgan. Jarred, thanks for being back on the show.
[00:00:13] Jarred Morgan: Happy to be here of course. And it's summertime, so, the kids are out of the house. It's great.
[00:00:17] Eric Knight: They're out of the house. That's why we're taking advantage of this moment. Right now.
[00:00:21] Jarred Morgan: It's quiet.
[00:00:22] Eric Knight: We have to be quick. We don't know how much time we have. But this is an important topic today because we've been getting a lot of questions about it. Temperatures are heating up. We're gonna talk about water temperature today. Specifically because we've been getting a lot of phone calls about "I can't hold chlorine in my pool."
[00:00:36] "My chlorine! I'll add chlorine, it's not there in a week. I don't know how, I don't know why it's disappearing." And for some reason, most people think that they need more cyanuric acid if that's the case. So in today's episode, we're gonna talk about the relationship between water temperature, cyanuric acid, and pH. You ready to get into it Jarred?
[00:00:54] Jarred Morgan: Cannot wait.
[00:00:55] Eric Knight: Oh, I can tell. I can just hear it in your voice. All right. Let's get into it. Episode 70.
[00:01:03] Okay I guess I could summarize what I want to say here in one sentence, but we're gonna have to kind of explain that sentence. There is a difference between using chlorine and losing chlorine. Jarred, what do you think I mean by that?
[00:01:38] Jarred Morgan: Losing chlorine?
[00:01:40] Eric Knight: Using versus losing. Yeah.
[00:01:42] Jarred Morgan: Uh, using, in my opinion would be bather load driven, leaves falling in, organic loading that is consuming, quote unquote, the chlorine in the water and making it oxidized and sanitized as it should.
[00:01:56] Right. And mm-hmm, losing, in my opinion, would come from UV degradation and leaks. Dilution... rain diluting it out. Uh, that would be losing it in my book.
[00:02:11] Eric Knight: I think he nailed it. What do you think, audience? When chlorine is gone, let's say you're on a weekly route, like most pool professionals are. When you come back, if it's zero chlorine, you don't know when that actually ran out. You were in the service business. Do you think it lasted six and a half days? Five days? Two days? You have no idea, right?
[00:02:33] Jarred Morgan: No. We throw a bunch of chlorine in there, on your trip and cross fingers that you have something left.
[00:02:39] Eric Knight: Right. Now, the perfect amount of chlorine when you come back or, you know, just the dream is just like around one or even just less than one, just so you know that you're close to zero, but you actually made it through the week. Because if it's zero, you don't know when you hit zero, but if you have some, you're like, "all right. I had chlorine all week. That's pretty good."
[00:02:58] Jarred Morgan: And then repeat the process again, even though you might be adding way too much chlorine and oh yeah, it happens.
[00:03:03] Eric Knight: Yeah. Well, this is why overstabilization with cyanuric acid is such an issue. Because you have to put so much in. You know, we're aiming for that 7.5% of our CYA in free chlorine. And that's a huge amount if you're not taking care of phosphates, et cetera.
[00:03:19] If you're not following the four pillars, you need a lot of chlorine in that pool. And it's very hard to maintain that amount. And the more CYA you have, the slower chlorine will work, but the more you need. So it's kind of this catch 22, where you have to, uh, walk a fine line between how much CYA do you need and how much free chlorine do you need. So that, that ratio is optimal throughout the week. That's a tough thing to do.
[00:03:44] Jarred Morgan: Yeah. And CYA is a topic that, everybody has a different opinion. But we really don't have a bone in that game as far as we don't produce CYA. We don't have any products that contain CYA. But we do get a lot of calls on it. It's it's a, a lot of calls.
[00:03:59] Eric Knight: Oh yeah. Well, see, warmer water tends to mean that chlorine doesn't last in the pool as long in general. And so the conventional wisdom in the industry is "Okay it's summertime. I can't hold chlorine. I must need more cyanuric acid. I must be losing it to the sun because it's a hotter day."
[00:04:17] I hear it all the time. "Oh, it's so hot. I just can't hold chlorine. I need more CYA." But that's not really about water temperature. Is it Jarred?
[00:04:26] Jarred Morgan: What, CYA?
[00:04:28] Eric Knight: The loss of chlorine.
[00:04:31] Jarred Morgan: What do you mean?
[00:04:32] Eric Knight: Well, it's not really a trick question here. I guess I should rephrase the question.
[00:04:35] Jarred Morgan: Yeah. Cause water temperature is a pretty important factor here.
[00:04:39] Eric Knight: Well, it, it is, but not for CYA performance.
[00:04:44] Jarred Morgan: Correct.
[00:04:44] Eric Knight: It's a very important factor in just about every chemistry. It has almost nothing to do with how cyanuric acid protects chlorine from sunlight.
[00:04:51] Jarred Morgan: No.
[00:04:52] Eric Knight: Now maybe some negligible amount at much colder temperatures, because it's slower to bind. But when you put chlorine into a pool that has CYA, the binding is really quick. At colder temperatures, maybe it's longer, but still it's kind of negligible. It's not like chelation, which takes hours or even days. The binding to CYA is very, very fast. And the water temperature really has nothing to do with how well it's protected from sunlight.
[00:05:19] It's a coincidental relationship. So people see the result and they equate it to "the temperature's higher. I can't hold chlorine. That must mean that I'm losing it to sunlight." That's not what's happening.
[00:05:32] Jarred Morgan: They also see the direct relationship between having a higher cyanuric acid and continually having a chlorine residual when they come back. Right. So there's this false perception that gives people a nice, warm and fuzzy feeling.
[00:05:47] Eric Knight: That is absolutely correct. Expand upon that. Why are they seeing that?
[00:05:52] Jarred Morgan: Because when you are...
[00:05:53] Eric Knight: you got this, Jarred, I believe in you.
[00:05:54] Jarred Morgan: In chemistry, water temperature, as it increases, speeds up chemical reactions.
[00:06:00] So you're gonna have a faster reaction as your water warms up. And that also includes faster reactions with chlorine.
[00:06:07] Eric Knight: Mm-hmm. So, in other words, if I can distill what you're saying, CYA is allowing you to hold chlorine in the hot summer because it's slowing chlorine down.
[00:06:16] It's putting the brakes on. Now, it's not killing as effectively. This is the risk you run because it is slowing down the kill rate. But you will, at high enough CYA levels of course, you will be able to hold a free chlorine residual that you can test for.
[00:06:32] Now was it effective? Was it faster than the growth and reproduction rate of algae?
[00:06:36] Jarred Morgan: Yeah. Do you wanna make that trade?
[00:06:38] Eric Knight: That's the fine line that you have to walk. You have to sort of weigh the options of deliberately slowing down chlorine's performance and protecting it from sunlight so that you can get it to last seven days.
[00:06:50] Now what Jarred is saying is absolutely correct. Because water temperature does accelerate reactions. Chlorine is being used up. It is working better. It is working faster. It is doing its job. That's why you're not seeing it at the end of the week, but you're not losing it to direct sunlight. If you've got appropriate CYA levels.
[00:07:14] Jarred Morgan: Which, just to clarify here, what is cyanuric acid's main job in a swimming pool?
[00:07:20] Eric Knight: Is that a serious question?
[00:07:21] Jarred Morgan: I'm asking you. Yeah. It is to protect the...
[00:07:25] Eric Knight: Oh are you answering it now? You didn't even give me a chance to answer. I was confused.
[00:07:28] Jarred Morgan: You asked me the question as if...
[00:07:29] Eric Knight: I thought you were kidding. Was it not a rhetorical question to the audience, Jarred?
[00:07:33] Jarred Morgan: I'm not good at talking to the audience. So yeah. What is cyanuric acid's main job in the pool?
[00:07:42] Eric Knight: It is to protect free chlorine from degradation from sunlight.
[00:07:46] Jarred Morgan: UV. That's it.
[00:07:47] Eric Knight: Nailed it.
[00:07:49] Jarred Morgan: There you go, everybody. Adding more is just gonna give it more protection from sunlight. Which it doesn't really require a whole lot to do that.
[00:07:58] Eric Knight: Yeah. I mean, after 50 parts per million, talk about diminishing returns. You get very little benefit over 50. That's why we recommend 30 to 50 in residential pools.
[00:08:07] Or we just say 50 or less is pillar four. Cause you really don't need to go over that. You could, but everything over 50, uh, it's really just slowing your chlorine down, but maybe that's what you need to do. Like I was saying earlier, maybe that's your goal so that you can get through the week.
[00:08:22] But if you're gonna do that, we strongly advise keeping your phosphates as low as possible. We strongly advise getting organics out of the pool. Minimizing your oxidant demand. Minimize chlorine's job so that you have it in residual to stay, uh, present so that it can fight reproducing living things that only chlorine can kill. That's what you really need chlorine in there for. So, anyway, I don't want to get too far down in those weeds.
[00:08:49] Jarred Morgan: Well, there are a few things that I do wanna touch on. Everybody needs to understand that whether they purposely add more cyanuric acid to hold onto their chlorine longer, right, they need to understand that there's trade offs with that. Like you just discussed on the chlorine speed and so forth.
[00:09:04] But there's also an impact on the LSI. The higher your cyanuric acid goes, the farther it's gonna push your LSI down. So make sure you're taking that into consideration. Also, you need to understand that the higher the sin acid goes, this is a cumulative number. It builds and it builds and it builds and it builds.
[00:09:22] So if you purposely go in and add more, thinking you're gonna keep the chlorine around longer. You're also gonna accumulate more for later in the season. Or early part of next year. Or the year after. So this impact can be detrimental down the road. So long term byproducts and effects. Keep that in mind.
[00:09:43] Eric Knight: There is one more thing that we need to talk about. This is a little bit more complex, but if you look at our blog, uh, blog.orendatech.com. Search CYA. Find this article about water temperature and CYA. It's explained in there with a graph that should make a little bit more sense.
[00:09:59] Basically, there are two types of chlorine. Once chlorine gets into water, there's the strong, killing form, hypochlorous acid (HOCl). And there's the much weaker form called hypochlorite ion, which is (OCl-).
[00:10:12] Jarred Morgan: Which still does something.
[00:10:14] Eric Knight: Yeah, it does. And it it'll read, it'll read on a test kit for sure. So when you're testing free chlorine, both show up.
[00:10:21] But one is just like a hundred-some times slower than the other. Here's why that matters. When we talk about chlorine's strength, we're talking about the percentage of hypochlorous acid. Of HOCl. That's the killing form. That's the strong, badass form of chlorine. That's what you want.
[00:10:40] Nobody really talks about hypochlorite ion because it's so much weaker and yet it does read on a test kit. We talked in many previous episodes that if you have cyanuric acid in your pool, the strength of your chlorine is not really pH-driven. And that's true because if you look at that chart, the percentage of hypochlorous acid is already below 3% anyway.
[00:11:05] It's so low because HOCl is bound to CYA. It's a totally different chemistry. Now, what I'm saying is, as the pH gets higher, Specifically over 8.0, you really start to notice it around 8.5 and up. If your pH gets that high, the hypochlorite ion will actually break apart from CYA. It's gonna leave it.
[00:11:31] It's gonna say, Nope, I don't need you anymore. And it's gonna be exposed to the sun and it's gonna get burned out by the UV rays of the sun. That is free chlorine that you are losing if the pH gets high enough. Now it wasn't the good killing form of chlorine either. So it's not like it's HOCl letting go of CYA to kill something real quick.
[00:11:50] It's hypochlorite ion that takes forever to kill something. And so if your pH, in summary, gets too high, specifically over, I'd say about 8.5 if you look at the graph, if it gets over 8.5, you're gonna lose it to sunlight. If it happens during the day.
[00:12:07] Jarred Morgan: So my first opening statement was not completely accurate.
[00:12:13] Eric Knight: Oh, it was, it was accurate. Except you didn't read the show notes all the way to the end there. Jarred, because we discussed in the last episode that you got through college by watching the YouTubes instead of reading.
[00:12:22] Jarred Morgan: True.
[00:12:23] Eric Knight: But let's be honest. I only wrote five bullet points on this one. Which was a lot more than last episode. I'll give you credit where it's due. You didn't get to number five.
[00:12:31] Jarred Morgan: Well then good. I'm glad you clarified that on the pH as a factor with the, uh, chlorine strength and how it interacts with cyanuric acid, because. I'm just, uh,
[00:12:42] Eric Knight: poor boy. I need no sympathy.
[00:12:44] Jarred Morgan: Well, no, I maintained pools and this was just, you're right.
[00:12:46] The chart was, the higher, the pH goes is gonna have a relationship with losing chlorine, because technically you will lose, but
[00:12:54] Eric Knight: you will at higher pH's.
[00:12:56] Jarred Morgan: Let's just hope nobody's pool is hanging out at 8.5 pH because you're gonna have a bunch of other problems that go with that.
[00:13:03] Eric Knight: Yeah. Your LSI is gonna be really high and that's exactly right. So what I'm saying is water temperature isn't controlling the rate of loss. Because water temperature isn't a part of how well CYA binds to chlorine.
[00:13:15] The pH will be because the weak form of chlorine is gonna break off and leave CYA and it's gonna see sunlight and disappear. That's what you need to be aware of. So it's not water temperature, it is a high pH. But again, that's not about chlorine's strength. All right? Keep that in mind.
[00:13:32] Um, but again, look at the chart. I know that's thoroughly confusing, but you know, we could have probably done that better, Jarred. We, uh, we try to simplify chemistry here, but we tried.
[00:13:43] Jarred Morgan: Sometimes chemistry is just complicated.
[00:13:46] Eric Knight: Yeah, it is a dry subject even though it's water chemistry. All right. Can you summarize this episode for the fans?
[00:13:53] Jarred Morgan: Well, fans, cyanuric acid, chlorine,
[00:13:58] Eric Knight: ...a little more energy. There's more than 10 of them now.
[00:14:00] Jarred Morgan: Oh, pH, are the main factors here that we're dealing with when it comes to chlorine strength, whether it's gonna hang around or not. And then as that water temperature goes up or down, it is not having an impact on how much protection the cyanuric acid gives your chlorine. Period. Right?
[00:14:16] It's just as things in chemistry happen, the higher the water temperature, the more things speed up. And as that water temperature goes down, the slower things get. So that is the reaction that you're seeing when we get into the summer and we start burning through chlorine. It's because that water is getting hotter.
[00:14:32] Eric Knight: Mm-hmm it is getting hotter and chlorine is working better. So yeah, I think you summarized it very well.
[00:14:38] Uh, this has been episode 70 of talking about water temperature, CYA performance, and pH. If you have further questions on this, feel free to reach out: podcast@orendatech.com. You can also go to our new help center. Jarred, we should probably do an entire episode on our help center. ask.orendatech.com.
[00:14:57] A lot of good information in there. It will soon be on our website. We're doing this whole website overhaul right now. An app overhaul right now. We're doing so many different projects trying to get a ton of information out all at once. So it's a little chaotic on our end, but thank you for listening and we hope to hear you on the next one. Take care everyone.