Bob Lowry: The Truth About Persistent High pH in Pools

Your pool pH isn’t “random” or “stubborn” and once you understand what’s actually driving the rise, you can finally stop the endless acid cycle. We dig into the real reason pH climbs week after week: CO2 off gassing. Total alkalinity controls how much carbon dioxide wants to escape, and when alkalinity is too high, the water is essentially overcarbonated. As CO2 leaves the water to reach equilibrium with the air, pH rises, and the problem repeats.

We also get honest about the pools that fight you the hardest: feature pools with negative edges, spillways, waterfalls, scuppers, rock cascades, spa jets, and blowers. All that aeration and turbulence accelerates CO2 loss, which means faster pH drift no matter how “perfect” your numbers look on paper. You’ll hear a simple spa-style experiment that makes the aeration effect impossible to ignore, plus the hard truth that some extreme designs may require a CO2 injection system if you want truly stable pH.

Saltwater chlorine generator pools add their own twist. We explain how SWGs raise pH through hydroxide production and continuous aeration inside the cell, then talk through practical ways to reduce generator runtime by cutting chlorine demand. That leads into borates, cyanuric acid strategy, and why dialing in free chlorine as a percentage of CYA can work better than a one-size-fits-all target. We also clear up a long-running pool chemistry myth: liquid chlorine and calcium hypochlorite don’t create a lasting pH rise after chlorine is consumed.

If you want fewer corrections, steadier readings, and a repeatable method for controlling rising pool pH, hit play, then subscribe, share this with a pool owner or pool pro who’s fighting pH, and leave a review with your biggest pH question.

We break down why pool pH keeps rising and why the real driver is often CO2 off gassing tied to total alkalinity and aeration. We share practical targets and field-tested fixes for salt pools, feature pools, and new plaster so you can stop chasing pH every week.  
• total alkalinity controlling CO2 off gassing and pH drift  
• why high TA makes pH rise faster and more often  
• setting realistic TA targets and lowering TA to stabilize pH  
• how waterfalls, spillways, negative edges, jets, and turbulence push pH up  
• when a CO2 injector becomes the only realistic path  
• saltwater chlorine generator effects including hydroxide production and aeration in the cell  
• using borates to reduce chlorine demand and slow pH rise  
• balancing cyanuric acid and free chlorine as a percentage strategy  
• plaster hydration in new pools raising pH for months  
• why liquid chlorine and cal hypo do not cause lasting pH rise after chlorine is spent  
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Transcript

Welcome And What We Solve

SPEAKER_00 0:14

Hey, welcome to the Best of the Pool Guy podcast show. In this episode, Bob Lowry is going to cover high pH in the pool. Actually, he's going to talk about constant high pH in the pool, which is a problem that a lot of us deal with out there. It'll offer you some solutions to pools that have constant high pH. Are you a pool service pro looking to take your business to the next level? Join the Pool Guy Coaching Program. Get expert advice, business tips, exclusive content, and get direct support from me. I'm a 35-year veteran in the industry. Whether you're starting out or scaling up, I've got the tools to help you succeed. Learn more at SwimmingPoollearning.com.

SPEAKER_01 0:52

I get asked this all the time. They say, how come the pH in my pool is going up all the time? My answer usually is, well, probably because your alkalinity is too high. The alkalinity that's in the pool controls the amount of CO2 that offgases out of the water. I want everybody to understand that the control of CO2 off-gassing is alkalinity, as the pool has too much carbonation in it already. It's overcarbonated. Slowly over time, the CO2 that's in the pool wants to come into

CO2 Off Gassing Drives pH Up

SPEAKER_01 1:40

equilibrium with the CO2 that's above the pool. They need to be in equilibrium. And because there's too much CO2 in the water, it gases off. And when the alkalinity is low, it gasses off a little bit. When the alkalinity is high, it gases off a lot. So when the alkalinity is high, it gases off CO2. When it gasses off CO2, the pH goes up in the pool. If the alkalinity gets high, now we have we have off-gassing happening more often, pH goes up. So if we get the alkalinity down, it doesn't gas off as much. The industry has a standard that says 60 minimum, 80 to 120 is ideal, and like 160 or 180 is maximum. And that's just total BS. That's way, way out of the range of where it should be. And 60 might be okay for a minimum, but the maximum is way, way too high. We set a system of targets when we teach this, and the target for total alkalinity is 90. People say, well, is it always 90? And the answer is no, it could be less. And they go, well, can it be higher? And I go, not usually. The 90 is where it should be. But if your pH is always going up and you have an alkalinity of 90, then maybe you should make your total alkalinity 80. And see if 80 doesn't keep your pH from going up so much. And so, and you can actually go down to about 70. And the idea is to keep the pH stable. We don't want anything that's going to raise the pH. And we also don't want anything that's going to cause the CO2 off-gassing to happen any faster. And what happens is people have negative edge pools, they have waterfalls, they have spillways, they have scuppers everywhere dumping water into the pool, and it looks great, and it looks cool. They have these rock features, and the water all dribbles down the rocks, and it looks really cool. The problem is

Total Alkalinity Targets That Work

SPEAKER_01 4:05

it increases aeration and turbulence and CO2 off-gassing. And when it does, the pH goes up. If you don't believe that, you can do your own little experiment. It's real easy to do. Take a spa and go out and measure the pH and take some dry acid with you and dump in a little bit of dry acid until the pH gets to be 7.2. Now, once it's 7.2, turn on all the jets and all the blowers and set a and look at your time, set your watch for about 10 minutes and go do something else for 10 minutes and come back in 10 minutes. And I promise you the pH will be a minimum of 7.8 when you come back. And it probably will be 8.0. And that's because of aeration and turbulence. So the more aeration and turbulence there is, the faster the pH is going to go up. And you can prove it in a spa. And so the same thing happens in the pool. If you've got a bunch of waterfalls and rock formations and spillways and negative edges, I had a guy call me one time and said, I've got a 316-degree negative edge pool, and the drop on the negative edge pool is eight feet. And I go, you're never going to get the pH down, ever. If you get it down, it's going to be for five minutes and it's going to go back up. It's not going to be possible unless you decide to put in a CO2 injector. And that way you got CO2 leaving the pool and you got CO2 coming into the pool, and they're going to cancel each other out, and you're going to be able to keep the pH where you want. But that's the reason. And then, as we've also talked about today, with the saltwater chlorine generator, it makes sodium, it makes hydroxide in the water. It also makes hydrogen gas. And the gas is a bubble, and therefore it's aeration. And because there's a lot of plates and cells in the generator, there's turbulence. So you've got turbulence and aeration in the cell, and it's continuous all day long. And so now you've got turbulence and aeration in the chlorine generator, and it's making hydroxide. Both of those things raise the pH of the pool. The only way to have it not do that is to have the chlorine generator not run so long. You do that because you keep a higher chlorine level, or you add something like borate to the pool that will cut down the amount of chlorine that you need. Borate works as an algostat, and therefore, because algae gets introduced into the pool, the borate prevents it from propagating, from reproducing. So the chlorine doesn't have to. So you don't need as much chlorine, so you can run the chlorine generator less time. Less time means less hydrogen gas produced and less sodium hydroxide produced. So the other thing is that borate in the pool keeps the pH from going up as fast or as high. So borate in the pool will help with keeping the pH from going up. And the final one is plaster hydration. And that's just a plaster pool is brand new. The plaster is hydrating and curing. And in that process, it raises the pH

Water Features Turbocharge pH Rise

SPEAKER_01 7:40

because it adds a lot of alkalinity to the pool. So it's just a fact of the matter. But eventually that slows down because it gets cured, and then the pool doesn't do that as much. It still may do it. You know, the older the pool, the less it does it.

SPEAKER_00 7:57

And I think the curing process can be anywhere from six months to a year. Is that correct? That's correct.

SPEAKER_01 8:02

Yes, it yeah, it will do that for, and it may even go on longer than that, depending on temperature and and so on. If it's a colder temperature, it may take may take longer.

SPEAKER_00 8:16

Let's touch on the borates one more time, because I know you you just briefly touched on it when you were talking about a saltwater generator. Now I have I have a saltwater pool, I have a spillway, and I have my alinate at 80, and I have borates in my pool at 50 parts per million, and I check my pH once a week. I checked it on um a week ago with a 7.7, and then I checked it after one week as a 7.8, and I have all these things going. Of course, my saltwater generator is only set at 20%. Right. And so would all these things go in my pool and it's 14,000 gallons. The pH barely went up in a week, which is probably, you know, with all these factors set this way, would probably work for a lot of people. Is that correct?

SPEAKER_01 9:00

Actually, from field experience and and guys like you calling me, we have come to the reality that with a saltwater chlorine generator, that 70 parts per million of borate is actually better than 50. But again, I have to give you a warning that that the EPA says the maximum borate in the pool should be 50. So, but EPA also says that the maximum CYA in the pool should be 100. So, and we've got pools of three or four hundred in there, and people aren't dying. So 70 seems to work better. And also we found that a slightly higher cyanuric acid level works better too. And that has to do with the fluid dynamics, and that is that the chlorine generator is making an amount of chlorine, and the amount of water that's near the chlorine generator has cyanuric acid in it, and we want the chloride, the chlorine to attach to the cyanuric acid before it gets back to the pool, because sunlight destroys chlorine and water very quickly. So we found that that all of the chlorine is not attached to cyanuric acid when there's only 50 parts per million in there. So we increase the cyanuric acid level up

Salt Systems Raise pH Two Ways

SPEAKER_01 10:30

to 70 and the borate to 70, and both of those two things allow you to use a whole lot less chlorine in the pool so that you can run your chlorine generator at you know 20% or something like that. It's a great way to do it. And then we need to keep the chlorine level needs to be a percentage of the cyanuric acid and not what the recommended level of two to four parts per million of chlorine. That doesn't always work. And the higher the cyanuric acid level, the more chlorine you need in the pool.

SPEAKER_00 11:09

Yeah, and I was gonna say, I was saying that the bories are also a secondary buffer to pH, right? That's correct, right?

SPEAKER_01 11:15

They keep the pH from going as high or as quick.

SPEAKER_00 11:20

Yeah, before I added the borates to my pool about six years ago or seven years ago was when I first added the bories to the pool, I was always battling the pH. It was never as stable as it is now, even with the lower generator output, because the borates really do keep the pH stable in the pools. And I I found that to be true in all pools, not just saltwater generator pools. So one of the last things here I wanted to touch on was in the tech bolton it talks about liquid chlorine not raising the pH, where it does raise it, but it's only a temporary. And you also mentioned that cal hypo, and this is something that's new to me, uh, because I always thought when you add cal hypo, you have to compensate with some muratic acid, just like when you used to add liquid chlorine. But you're also saying in the tech bolton that the cal hypo does not raise the pH up in the pool and it doesn't stay up, right? Right.

SPEAKER_01 12:10

Yeah, it's the same principle for cal hypo and for liquid chlorine. And technically it would be the same principle if you had lithium hypochloride. Lithium hypochloride raises the pH too. But but here's what for many years, I even in my books I wrote if you use liquid chlorine, you're gonna need to add this amount of uh acid to compensate for it. And and then we started thinking beyond just adding it to the pool. What happens? As most of you people know,

Borates And CYA For Stability

SPEAKER_01 12:45

when you add chlorine to water, it makes the killing form of chlorine called HOCL. And it's called hypochlorous acid. But that's the killing form of chlorine, it's HOCL. We didn't realize, but tomorrow or this afternoon, when the sun comes out, the chlorine gets degraded, even with sineric acid in the pool, the chlorine gets degraded by the UV light from the sun. And so the HOCL, when it degrades by UV, it degrades from HOCL to HCl. So the O goes away. And so the oxygen goes away from hypochlorous acid and it becomes hydrochloric acid. And the amount of hydrochloric acid that is made is almost exactly equal to the amount of sodium hydroxide that was added when you add the product. And so they cancel each other out. And it's the same with cal hypo, liquid chlorine, or lithium hypochlorite. They all do that same thing. And there is, depending on the manufacturer, there is a slight excess of hydroxide in their product. The when they make liquid chlorine, the controlling factor for how much chlorine they can put in that liquid is the hydroxide. So they control how much how much chlorine is in that that bottle by how much sodium hydroxide

New Plaster And Ongoing pH Rise

SPEAKER_01 14:35

is in it. So they put us a little bit of excess of sodium hydroxide in there, but the amount that's in there, believe it or not, is 0.03%. A hundredth of one percent excess. And if you calculate that excess, it's the equivalent out of a gallon of you adding about a third of an ounce of hydroxide to the pool. To a 15,000 gallon pool, which is not enough to change the pH hardly at all.

SPEAKER_00 15:19

That's interesting. I you know it's one of those things that I think people have I still get comments all the time when I because I've posted these podcasts on YouTube and I've also talked about a year or a year or two ago when I did a overview of chlorine types, I mentioned the fact that liquid doesn't raise the chlorine, I mean the pH in the pool, and I still get comments from pool guys. It's it raises it, you know, you're wrong. I think that's not

The Truth About Chlorine And pH

SPEAKER_00 15:45

really sinking in yet to the industry.

SPEAKER_01 15:47

Yeah, we did a we did a video on a bucket test, and we put in the equivalent of five parts per million of chlorine, and we put it in a five-gallon bucket, and we measured the pH that it created, and we we put it in the sunlight, left it outside, and brought it back in the next day, and the pH was exactly where we started the day before. With with a uh with a pH meter. Yeah. And so we lost all the chlorine, and the pH was exactly where it was before we started the day before.

SPEAKER_00 16:24

If you're looking for other podcasts, just go to my website, swimming for learning.com. On the banner's a podcast icon. There'll be a drop down menu with over 1900 podcasts for you there to listen to at your leisure. If you're interested in the coaching program, you can learn more at pullguycoaching.com. Thanks for listening to this podcast. Have a rest of your week. God bless.