After a brief overview explanation of pH, we discuss what raises pH, and what lowers pH. In short, it's about dissolved CO2 in your water.
00:00 - Introduction
00:38 - Overview/recap of what pH is and what it means
02:30 - pH dogma in the swimming pool industry, debunked
05:24 - pH is about dissolved Carbon Dioxide (CO2)
06:37 - pH ceiling (when CO2 is equalized between water and air)
07:16 - What raises pH?
11:14 - What lowers pH?
13:48 - pH suppression
15:13 - Summary. Thanks for listening!
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91. 1 | What raises and lowers pH?
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[00:00:00] Eric Knight: Welcome everybody to the first of our seven part series on what raises and lowers specific chemistries. This is episode 91, the first of the seven, and we are going to be talking about what raises and lowers pH. And just so you know, we cover pH in more depth in our episodes. 1, 3, 29, 31, 35, 46, 70, 77, and 79.
[00:00:31] As you can tell, it's a pretty important thing to understand. So let's go.
[00:00:38] pH, as a refresher, stands for potenz Hydrogen, but in English, that's power of Hydrogen. Basically, it's the concentration of Hydrogen ions. And so the more hydrogen that's attached to a given compound, the lower the pH and the more acidic it is. And then conversely, the less hydrogen attached, the higher the pH, and the more basic or alkaline it is.
[00:01:21] pH is on a 0 to 14 scale where 7.0 is perfectly neutral and every whole number is 10 times greater or less than the next whole number. So like if you are at a six and you go down to a five, that's 10 times more acidic than six, but because it's logarithmic, four would be 10 times 10, right? So the difference between four and six is actually a hundred times more acidic.
[00:01:47] The difference between three and six is 10 times 10 times 10. That's a thousand times more acidic. So it can get out of hand pretty quickly. Now, if you think about an H2O molecule, the hydrogen separates from it. You get this Hydrogen ion, that's the acid, and then the (OH-) with an electron on it is the hydroxide. That's the base.
[00:02:09] If you have an (OH-), a hydroxide in it, you're going to have a very high pH. Things like calcium hydroxide, or sodium hydroxide. You know that it's got a very high pH. So just keep that in mind. We don't want to get too deep into that chemistry here, but I do want to bring it up because pH matters because it impacts just about everything. In water chemistry.
pH Dogma in the swimming pool industry
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[00:02:30] Eric Knight: We at Orenda care about it mainly because of its impact on the LSI. Though the industry has been taught what I call pH dogma, where the three main reasons for thinking about the pH come from the industry standard textbooks and stuff. Where it's like bather comfort, the pH of your eyes or skin or whatever; corrosion and scaling of equipment; and the strength and efficiency of chlorine. And I can just debunk all three of those.
[00:02:58] So bather comfort: that's not true at all. I was a competitive swimmer for a decade of my life, and I've swum in pools with 6.5 pH in Europe, and it felt fine. And I've also been in horribly mismanaged pools in the United States that had higher pHs. And I know this because I can drink bottled water at 5.5 pH and I can also drink Costco water at 9.5 pH, and they're fine. Well, that's a 10,000 times difference in acidity. And both are fine. They don't irritate me at all. Now to the extremes, yes, a pH can itch your skin and it can burn you eventually, but it's not about the pH of your eyes. It never was.
[00:03:38] Bather comfort is about disinfection byproducts. It's about chloro-organic compounds and combined chlorine and things like that. That's what bothers swimmers. It's not the pH. So I don't buy that argument at all. If you can prove me wrong, podcast@orendatech.com is the email. State your case. I'll hear you. I'll read it. I'll respond. I'd love to know.
[00:04:03] The next one. Corrosion and scaling of equipment. This involves pH, but it's not just the pH, it's actually the LSI. So it's the pH and the other factors that go into the LSI. That one, uh, I don't need to dwell on.
[00:04:15] And then finally, chlorine strength and efficiency. We really dive into this in several other episodes, but basically that's true that the lower the pH, you will have a higher concentration of hypochlorous acid, which is the stronger form of chlorine. If you have zero cyanuric acid in your water. The moment you introduce cyanuric acid to your water, that changes everything.
[00:04:40] You can listen to more episodes about that and go on our website. Just type in CYA in our blog. You'll find a ton of information on it. We have this chart that we got, Uh, we didn't write the chart, actually, we got it from the Model Aquatic Health Code. And it clearly shows that when you have CYA in your water, the pH is not controlling the strength of your chlorine. The free chlorine to cyanuric acid ratio is.
[00:05:06] So this pH dogma that you have to have a 7.4-7.6 pH uh, not buying it very much. It really matters for your LSI though. So I'm not saying it's not important, I'm just saying it's not important for the same reasons we've been taught. Especially if you have cyanuric acid in your pool.
pH is about dissolved Carbon Dioxide (CO2)
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[00:05:24] Eric Knight: But an easier way to think about pH is to think about dissolved carbon dioxide. Again, we have another episode about this or like five. The more dissolved CO2 in your water, the lower your pH. And the less dissolved CO2 in your water, the higher your pH.
[00:05:42] I like to think of beer in a bottle. If you're looking at the bottle, you don't see any bubbles, but as soon as you crack that bottle open, suddenly bubbles appear and they start getting to the top, and you get that head foam. And eventually the beer goes flat. Because you're witnessing something called Henry's Law. And basically all it states is any gas dissolved in a liquid must equalize with that same gas above that liquid.
[00:06:07] In that compressed bottle, you had that little pocket of air under high pressure because there was a lot of CO2 in the beer, a lot of CO2 in that pocket of air. You open the beer. Now the CO2 and the beer has to equalize with the room, which is a much lower pressure, therefore it loses CO2.
[00:06:26] And because CO2 determines the pH in your pool, when you lose CO2 to natural aeration and offgassing, your pH naturally rises.
pH Ceiling
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[00:06:37] Eric Knight: This is why we added the pH ceiling to our app. If you push show on secondary readings at the top left of the calculator, it's going to show you how high your pH can naturally go. That pH ceiling is basically how high your pH can go when your CO2 is in equilibrium in the water and the air above the water. Meaning you can't lose more CO2. That's the ceiling. That's it.
[00:07:02] Just like a beer will go flat after a while, your pool is trying to go flat too. When your pool is flat, that's what your pH is going to be. You could get over it, but you'd have to force your pH over it. It's not naturally going to get there.
What causes pH to increase?
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[00:07:16] Eric Knight: So now that we've done that recap of pH, let's talk about what causes pH to increase? In order to raise your pH, you need to lose CO2. You need less carbon dioxide in your water. You can do this with aeration: jets, spillways, waterfalls, bubblers, sprayers, people splashing, you name it. That is going to accelerate the loss of CO2 and raise your pH.
[00:07:45] What else gets rid of CO2? Hmm. Well, believe it or not, a salt chlorine generator will off gas CO2 inside the cell because it's off gassing hydrogen gas which causes turbulence and it off gases CO2. So CO2 leaves, and the pH goes up.
[00:08:06] Believe it or not, we did another episode on this. The chlorine gas that's produced inside that salt system almost perfectly neutralizes the hydroxide that is also produced, and that's basically a wash. So when you have this process, you're actually raising the pH in the pool because of the loss of CO2 generated in that cell. So it's actually the same thing.
[00:08:29] But there's another thing that gets rid of CO2. Algae! Algae consume CO2 because algae is a plant. Plants consume CO2. So just another thing to think about.
Chemicals that raise pH
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[00:08:42] Eric Knight: But there's also chemical additions that we can add to deliberately raise our pH. These are actually products like Sodium bicarbonate, or more specifically soda ash.
[00:08:55] Two different products. Sodium bicarb is baking soda, and it's used to raise your alkalinity. We'll talk about that in the next episode. And soda ash is sodium carbonate, which is used in much smaller doses to raise the pH. And it'll raise the alkalinity too, just you're not using nearly as much of it, so your alkalinity doesn't go up as much.
[00:09:16] If you are a residential pool owner or a pool professional and you do not have an acid feeder on your pool, you should probably never be using soda ash. We have it in our app for our commercial pool audience because they have chemical feeders and they may need to use it. But if you don't have an acid feeder on your pool, and you're not a 24/7 treatment kind of thing, don't use soda ash. You're likely to cloud up that pool. Let natural aeration raise the pH for you. It's physics. It's going to happen.
[00:09:49] But there's also the high pH of chemicals like chlorine. Now, this is a temporary rise in pH. Because if you put liquid chlorine in, which has a high pH of about 13, yes, for a moment it's going to have a high pH. And until the HOCl, the hypochlorous acid kills or oxidizes, you're going to have that high pH in the pool. But once it does kill or oxidize, the oxygen in that HOCl gets exchanged for an electron and you're left with HCl, that's hydrochloric acid, aka muriatic acid, it's almost a perfect neutralization.
[00:10:32] So once chlorine does its job, it actually becomes pH neutral. And a lot of people don't know that. And I got to credit people who have told us this. It is actually written in Bob Lowry's textbook. If you've ever read the IPSSA Basic Training manual, it's actually in there. It is a pH neutral thing. Same with Cal hypo. But if you are not using acid every week to reduce your pH, this excess lye that is created by these chlorines will accumulate. And you'll get excess hydroxides in your pool. Let's say you're using a CO2 feeder instead of acid, it will also raise the alkalinity. We're going to get to that in episode 92.
[00:11:13] So you get these high pH chlorines, cal hypo, liquid chlorine, and then of course salt cell raises it because the loss of CO2.
[00:11:20] If you have other high pH chemicals, they can, just depends on how much you dose. But realistically, that's not really a huge contributing factor.
Recap of what raises pH
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[00:11:28] Eric Knight: So the main things are natural loss of CO2 or forced loss of CO2, in the case of a salt cell. And then adding something like sodium bicarb or soda ash. Or the temporary rise of liquid chlorine or cal hypo.
What decreases pH?
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[00:11:44] Eric Knight: Now let's talk about what causes a pH to decrease. Well, in order to lower the pH in your water, if you have alkalinity in it, you need more CO2. You need more dissolved CO2 in your water. The easiest way to do this is to use a CO2 injector. But most pools don't have that. A lot of commercial pools do. But hey, if you need more CO2 to lower the pH, inject CO2. There you go. It'll lower your pH and it will not lower your alkalinity.
Acid lowers pH and alkalinity
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[00:12:16] Eric Knight: But the main way people lower their pH is they use acid. Acid will convert alkalinity into dissolved CO2. It will convert bicarbonate into something called carbonic acid, which is H2CO3. H2CO3 is H2O plus CO2. In other words, it's dissolved carbon dioxide. That's what lowers your pH.
[00:12:50] That's what lowers your pH. So when you put acid in a pool to lower your pH, you also lower the alkalinity. Because you're burning through the alkalinity to create more dissolved CO2. That's why they both go down. But if you just inject CO2 to lower the pH, the alkalinity doesn't go down because you bypass that step.
Trichlor and other acidic chemicals
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[00:13:14] Eric Knight: Another way you can lower pH: acidic chlorine like Trichlor. 2.8 pH. That'll lower your pH. And then other acidic chemicals, like to some degree sequestering agents or even our PR-10,000. But in the normal dosing that you're going to be using, that's going to be minimal. You're not using a ton of these products.
Recap of what decreases pH
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[00:13:34] Eric Knight: So it's not nearly as acidic as something like muriatic, or sulfuric acid, or sodium bisulfate. So generally what's going to lower it is going to be a CO2 injector, or acid, or trichlor.
pH suppression
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[00:13:48] Eric Knight: The final thing I want to talk about here is pH can also be suppressed. And in order to suppress the pH, all you have to do is prevent the natural offgassing of CO2. We did an entire episode on this, episode 46, by the way. But essentially you need to cap your beer. So there's one factor that we're not thinking about here. Every pool is naturally going to raise their pH, right? The pH is naturally rising. Except pools with auto covers.
[00:14:16] Because an auto cover that is not mesh, and by the way, for those cover companies that might be listening to this, I've talked to several of you already, if you can make a safety cover, like an automatic safety cover that is mesh that retracts and opens up and closes, but it's mesh to allow CO2 to escape and dilution to come in, that would be awesome.
[00:14:39] That would dramatically improve water chemistry for people with covers, because pools need to respirate. It's all about carbon dioxide. If that carbon dioxide cannot leave, and let's say you have a trichlor feeder on that pool, we actually got to get a lot of calls about this. That pH is going to be driving down, down, down, down, because the trichlor is driving the pH down. And the CO2 has no place to escape. The auto cover is preventing the loss of CO2. That's how you suppress the pH. Listen to episode 46 for more details on that.
Summary
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[00:15:13] Eric Knight: But to recap what raises and lowers pH. If you want to raise your pH, you need less CO2 in your water. If you want to lower your pH, you need more CO2 in your water. And the way acid creates more CO2 is it converts alkalinity into carbonic acid, which is dissolved CO2.
[00:15:36] So I hope this explains it. If you are having questions about why your pH is going up or down, think about CO2. Think about your beer going flat. Think about how you could stop CO2 from moving, or what could be accelerating it.
[00:15:50] I'm Eric Knight with Orenda, this has been episode 91. The first of our seven part series. I hope you found it valuable, and we're going to get through the rest of these week after week. If you have any questions, reach out to us: podcast@orendatech.com or try our help center, ask.orendatech.com. Thanks for your time.