Eric walks through the impact that pool covers have on pool chemistry throughout the season. In short, they block dilution and the off-gassing of CO2.
00:00 - Introduction
01:29 - Why pool covers change pool chemistry
03:09 - Rain and snow dilution
03:48 - Auto-covers and plaster issues
05:00 - Salt chlorine generators and covered pools
09:11 - Breathable pool covers?
10:08 - Trichlor feeders on pools with autocovers
12:55 - Creative ways to off-gas CO2 from a covered pool
14:43 - Closing
[00:00:00] Eric Knight: Hi, everybody. Welcome back to the Rule Your Pool podcast. I'm your host Eric Knight. And I'm doing this one alone. And I'm doing this one by the request of multiple customers in the last three or four weeks. It seems to be, you know, it's like questions that we get tend to come in waves. I don't know why that is.
[00:00:18] One week we'll just get hammered with questions about flakes in saltwater pools, or plaster discolorations, or green pools or whatever. Well, this wave was about auto covers. I'm going to go back 112 episodes, as absurd as that is, to episode 40, where we talked about pool covers and how they affect winterization chemistry.
[00:00:39] That episode stopped short of what we're going to talk about today, but it's a pretty good preface. If you want to go back and listen to episode 40. That's going to give you a little bit more context for what we're talking about here. In this episode, we're not just talking about winterization. We're going to focus instead on weekly service.
[00:00:56] And if you're a homeowner and you have an auto cover, what does that do? Why is that different from having a pool that does not have a cover? So with that in mind, this is episode 152 of the Rule Your Pool podcast.
[00:01:29] Eric Knight: I don't see a reason for this to be a very long episode. The fundamentals of this, in my mind anyway, are fairly straightforward. Two concepts I want you to walk away with from this episode. A pool cover blocks the loss of CO2, and it blocks dilution.
[00:01:49] Now we talked about this in episode 40, certainly over the winter, when you have a lot more time for rain and snow dilution, if you're in a cold area. That matters a lot more because we're talking five or six months of being closed. But what about the ongoing customers that have auto covers that may not winterize?
[00:02:05] We get a ton of these questions from areas like Northern California, the Northeast, especially, has a lot of these auto cover pools. And they can't necessarily be treated the exact same way as any other pool.
[00:02:18] I know we've said this before, but I'm going to say it again. The type of pool surface you have matters less than whether or not you have a cover on. And if you're winterizing, it matters less than the type of cover you're using, whether it be mesh or solid.
[00:02:33] The reason is exactly what I just said. Covers block the loss of CO2. At least solid auto covers block the loss of CO2. And they blocked dilution from getting in. Those are huge deals. They're going to affect your chemistry in bigger ways than whatever pool surface you have.
[00:02:51] Because if you have your pool balanced to the Langelier Saturation Index, the water shouldn't really be interacting with the surface at all. So it doesn't matter if it's in a vinyl liner, fiberglass, or plaster pool. That water should be in harmony with itself. Therefore it's not interacting in a negative way with what's around it.
[00:03:09] Eric Knight: But what it will affect is how that water interacts with the air above it. Or I should say the sky. If rain and snow get in there, which have zero parts per million calcium, that's going to dilute those factors down. It's going to dilute cyanuric acid, TDS, and everything else down because rain is basically distilled water. So is snow.
[00:03:29] But the loss of CO2 is really the crux of this episode. I think we can all wrap our heads around dilution not being there if the pool's covered. Hell, what's the point of having an auto cover? It's to keep things out. Leaves, pine needles, whatever. And it effectively keeps water out too. Whether that's the intention or not.
[00:03:48] Eric Knight: If you have been listening to this podcast for any amount of time, you're probably aware that people don't call us about their good pools. They call us with troubleshooting questions or help. Unfortunately, a lot of people call us to try to get them out of responsibility for problems that they caused, but that's not our role. We don't like that position. We don't want to be involved with that. Especially not plaster issues. Because we're not in the plaster business. We have a startup process, but people call us with cement questions all the time.
[00:04:14] And a lot of these cement questions, certainly enough that it's worth talking about on an episode, they happen to be on pools with automatic covers. The moment that I hear there's an automatic cover on the pool, my entire mindset of troubleshooting changes. Because now I want to know what is the chemistry going on under that cover? And how often is that cover being opened and being exposed to the air so that that pool can respirate?
[00:04:38] Yes I want to know the chemistry, but what is going on under that cover that's being held under that cover? There needs to be interaction between the water and air. It's physics. It's supposed to happen.
[00:04:49] Auto covers can be great. I'm not saying they're bad products. They are very effective at what they do. You just have to be aware of what they do. They change your chemistry game. I'll give you a few examples.
[00:05:00] Eric Knight: I tell customers this all the time. I'm going to say it again. This is my opinion, based on a lot of troubleshooting with a lot of you customers out there, many of you listening to this, thank you. Many of the problems that we see are on pools with auto covers that have salt systems on them. Let's talk about that just for a second. What does a salt system do?
[00:05:22] We talk about this in episode 57, the title of that episode is how salt chlorine generators actually work. And we also talk about it in 34 when we talk about calcium flakes. Just a quick summary of it, you're running salt water through a device that has metal blades on it that transfer electricity from blade to blade. And that's called a salt cell. And when you run electrical current through it, there's a process called electrolysis creates chlorine gas, a byproduct of hydrogen gas and a byproduct of sodium hydroxide.
[00:05:58] Now the sodium hydroxide has a very high pH, and the chlorine gas is a pure acid, so it has a very low pH. Those two neutralize each other. And a lot of people don't realize this, but salt systems are technically the most pH-neutral type of chlorine you can have.
[00:06:14] But that byproduct of hydrogen gas, which is not very soluble, creates a lot of bubbles. You've probably seen this if you've ever looked at a salt cell producing. A lot of bubbles come up. Those bubbles create turbulence which forces the loss of CO2. And when you lose that carbon dioxide, the pH goes up.
[00:06:33] The pH rises because of physics. It's rising because you are losing CO2 thanks to the turbulence created by the hydrogen gas bubbles.
[00:06:42] Now let's apply that to an auto cover pool. Where do those bubbles go? Oh, yeah, they blow into the pool. They're supposed to off-gas. But if you have an auto cover on it, the CO2 can't leave. So, what does it do?
[00:06:58] Dissolved CO2, in its aqueous form, a portion of that is going to be something called carbonic acid. We have talked about this in many episodes about alkalinity and buffering systems. We just talked about it with a pulmonologist and episode 149. Carbonic acid is essentially dissolved CO2, but not all of the CO2 in the water is carbonic acid. In fact, a very small amount of it is carbonic acid.
[00:07:26] If that CO2, that is oversaturated relative to the air above the pool, is unable to leave, you basically have a new equilibrium under that cover. Henry's Law takes effect, but it's under the cover. So that concentration is different. And it basically suppresses your pH. I don't want to get too technical.
[00:07:43] If the CO2 can't leave the pH doesn't go up. You're putting a cap on the beer and the beer will not go any flatter while you have it capped. If you remember the lesson from Henry's Law, we're talking about the CO2 in the liquid, meaning in the pool, equalizing with the CO2 above the liquid. Just like a beer goes flat, your pool was trying to go flat. But you just put a cover on it. So it can't go flat.
[00:08:09] And what will happen is that pH stay suppressed, but you keep generating more of this CO2 out of the water. How much depends on your carbonate alkalinity, and we can talk about that another day. But my point is that CO2 doesn't go anywhere. So it either suppresses the pH at best, or it drives the pH down.
[00:08:30] In any event, it's very hard to maintain LSI balance without that LSI going below -0.3 or on the Orenda calculator, red. And if you have a plaster type surface, the water is going to etch. We see this all the time.
[00:08:44] What gets me is how many people call us and show pictures of these otherwise pretty new pools under a year old, and they're just destroyed. It breaks my heart. Customers spent a lot of money on a really nice investment. You know, beautiful pool finish, and nice tile and all this stuff, and it just looks trashed. I hate seeing that. But yet we see it a lot. It's not a good look.
[00:09:11] Eric Knight: Of course the ideal is to have a mesh auto cover. That keeps the debris and stuff out and it's a safety cover, but it allows dilution in and it allows CO2 out. That doesn't exist as of right now. I have talked to some cover manufacturers. In fact, there is one who reached out to us who said, Hey, we do have these holes along the side. Which is great. Um, so if you have one of those covers that has the holes on the side, that's a cool little innovation.
[00:09:35] I don't know how effective it is, I've never seen any measurements on it, but it's certainly better than nothing. It's the best thing I've seen. And I think that's a great little feature. Hopefully it expands. I imagine we probably need more, but certainly some is better than none. Getting that CO2 out is very important. If you want to align your water with physics.
[00:09:55] If you interrupt physics with an auto cover, it's going to push back. That water is going to push back because, as I've said before, water is always trying to return to its natural state.
[00:10:08] Eric Knight: Disinfection is not natural either. And we want that. So it's not to say we can't have a cover. It's to say that we need to understand what a cover does, and then we need to act accordingly.
[00:10:18] Let's move on to trichlor because if you thought salt systems are complicated for auto cover pools, ohh boy. Trichlor feeders are way worse. And the reason for that is they're not just releasing CO2 that already was in the water. Trichlor is creating more CO2 because it's acidic, and it's neutralizing alkalinity in the water.
[00:10:39] Remember it's adding a hydrogen to that bicarbonate. That bicarbonate converts to carbonic acid, which is dissolved CO2. So you're actually creating more CO2. So this doesn't just suppress pH. This pushes the pH down. It forces it down because it's creating more and more carbon dioxide.
[00:10:57] Now there are ways to manage this, but most people don't really understand how to, and that's evidenced by the amount of photos I've seen from customers of just plasters that are completely wrecked because there's a trichlor feeder on an auto cover pool.
[00:11:11] It can be done, but, as they say, you're going to have to crack a few eggs to make an omelet. And I'm going to give you a really good example of this.
[00:11:19] Had a customer from the Northeast call the other day. Thank you, Patrick. And we had a conversation for a good 30 minutes. Very smart guy. He knows what he's talking about. And he called and he said, Hey, I just want to make sure I'm not crazy. Patrick, I'm not trying to put words in your mouth, I'm paraphrasing here.
[00:11:34] He tells me he's got a whole bunch of auto cover pools that have trichlor feeders on them. One in particular is what he was calling me about. He said that he has found that the way to manage the LSI on that pool, because it's hardly ever opened, it's on a trichlor feeder, he doesn't have a choice. He can't switch it to a liquid chlorine feeder or anything like that. It's a trichlor feeder.
[00:11:55] The only way that he's able to maintain this is he has about 150 to 160 alkalinity on that pool. And he also has 400 calcium. Interesting.
[00:12:07] Normally, if you look at the pH ceiling, that would tell you that pH is going to go through the roof. Except it has a cover on it. And so he was explaining his logic behind it. And it's very clear that Patrick understands Henry's Law very well. He can explain it just as well as I can. He understands what trichlor does. That it's acidic and it's going to be neutralizing alkali in the water, creating CO2 that doesn't go anywhere. He gets all that.
[00:12:33] He also knows that the CYA goes up as trichlor dissolves. All of that was taken into account in his strategy for this auto cover pool. And it was working.
[00:12:43] And so I guess my message here is, as long as you understand the processes, you have to do things a little bit different. Do you have to have 150 alkalinity in there? Maybe not. But you also don't have to have trichlor on there either.
[00:12:55] Eric Knight: He's making the best of the situation that is out of his control to regain control of it and kudos to him. Maybe be thinking the same way. You don't necessarily have to go way out of parameters or way out of the norm to make something work. To fit a square peg in a round hole. If you're able to change things, if you are able to make adaptations and talk to your customers about this, you might be able to have a lot of success with it simply by changing the variables.
[00:13:26] If you have a salt water pool, that's not necessarily a bad thing if you have maybe a timer that opens that cover or a signal that says, Hey, the cover is closed. Don't produce chlorine right now. And as soon as that cover opens, fire it up. That could work.
[00:13:41] You could put a degassing chamber in there. You know, those degassing chambers after an ozone system? Like a contact tank? That can help you get some of that CO2 out. One of our customers in Florida does a, it's kind of like one of those swamp coolers where it deliberately rains water through a bunch of baffles to create evaporative cooling and lower the temperature of the pool. But that creates a ton of surface area and a ton of turbulence that allows CO2 to leave.
[00:14:11] So they don't have that problem. They're trying to cool their water intentionally by using this chiller. And that creates the loss of CO2. So just be thinking about how can you overcome this reality that an auto cover, when it's closed, suppresses the loss of CO2?
[00:14:26] As long as you're thinking about that, and you understand that it's going to happen, whether you like it or not. The water is going to lose CO2 to equalize with the air above it. That's a fact. You can suppress it with acid, you can suppress it with trichlor, and you can close the cover. You're just interrupting it.
[00:14:43] Eric Knight: Make decisions based on the reality of what water's trying to do rather than what we hope it will do. And I think you're going to find that managing pools with auto covers is a lot easier than it seems. These problems are preventable. If you have any questions on how to prevent them, reach out to us. The help center is ask.orendatech.com. If you don't see the answer you're looking for there, you can check the website, but you can also go to the top of that help center. And there's a button that says, submit your question. Reach out. Let's talk.
[00:15:15] I appreciate you listening. I really do. I just get so much feedback and it makes my day that you invest your time to get better at this. I love that. I love working with people who are trying to better themselves, further their education and be the best that they can at their trade.
[00:15:29] And for the homeowners listening to this, kudos to you for wanting to be informed and make informed decisions. That's great. We love working with you. Thank you so much for listening. We do have a few more episodes coming up with Terry Arko, which I have not had on the show in quite a while. I'm looking forward to that. If you have any requests for the podcast, the email is podcast@orendatech.com. I'm your host, Eric Knight with Orenda and HASA.
[00:15:52] And I hope you found value in this episode. If you did, and you have not yet subscribed, please subscribe. We are trying to hit a milestone here. Tell your friends. If we do, we'll do a special episode on it. Thank you all so much. Have a great one. Bye.