Eric reads an article from onBalance by Kim Skinner, explaining the math for dosing soda ash vs. sodium bicarbonate to raise total alkalinity, and why alkalinity is measured in ppm of Calcium Carbonate.
[00:00] - Intro
[02:20] - Soda ash vs. Sodium bicarbonate
[04:51] - Alkalinity article by Kim Skinner (onBalance)
[07:51] - Orenda Chemiculator® accuracy
[10:26] - Closing
Read Kim Skinner's article HERE.
198. Soda Ash vs. Sodium Bicarbonate for Raising Alkalinity
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Eric Knight-1: Hey everybody, welcome back to episode 198 of the Rule Your Pool podcast. And this comes from a question that I got on the email address, which we've been getting quite a few good questions on there. That's ruleyourpool@gmail.com. And I have never really thought much about this one, which is why I'm doing an episode on it. This should be a quick one, and it's about the difference between sodium carbonate, also called soda ash, and sodium bicarbonate.
And if you've listened to me before, whether it's on this podcast or in a, a trade show classroom, or maybe even at a private training at your company, I've always recommended that residential service companies try to avoid using soda ash. And it's not because you're not qualified to use it. It's because of the reality of a residential pool service business. You just don't have the time. And soda ash needs to be dissolved slowly, and anybody who's used it before, if you add it too fast, you know what happens. You get carbonate clouding. It'll milk up the whole pool.
And the reason for that is it's a lot higher pH, and it's a lot more concentrated than sodium bicarbonate. And I, you know, I just, I kind of knew that, and it was taught. I actually learned it from Bob Lowry many, many years ago, and I just never really looked into exactly how much more concentrated.
Now, on the pH logarithmic scale, um, the difference between 8.3 and 11.3, or it's very close to 11.3 for soda ash, that's 1,000 times more alkaline. But that doesn't mean it's a thousandth of the dose to do the same thing. What we need to actually look at is its impact on alkalinity. And so what I want to do in this episode today is read through the Journal of the Swimming Pool and Spa Industry. This is an article written by Kim Skinner from OnBalance, and it is quite well-researched. And I did the math, and I realized, hey, this is awesome because the Orenda calculator already has this, which means all of your routing softwares that you're using that has the Orenda calculator baked in already knows this. So you're getting accurate answers.
But I thought I would go through and just read this so that you can actually see the math behind it. I never actually went this deep, so I'm excited for this. This is episode 198. Hopefully, it's quick of why the doses for sodium carbonate or soda ash are different from sodium bicarbonate, specifically on changing alkalinity, not so much for pH. Let's go.
[00:02:20] Soda ash vs. Sodium bicarbonate
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Eric Knight-1: As you can see here, I've got an article up here from poolhelp.com, and it's written by Kim Skinner many years ago. I guess he did this in 2019. And it talks about the concentrations of sodium carbonate and sodium bicarbonate. And we are all used to raising alkalinity with sodium bicarbonate, which is the recommended product for that.
It's also recommended for acid washes on plaster surfaces that you put a high concentration of bicarb in the water and rinse it off so that you neutralize the acid. A lot of people don't do that. But it's really helpful on startups as well. Soda ash, however, is a very different product. And soda ash is a lot more concentrated for one thing.
And it's really made, in my opinion, this is Eric's opinion here, it's really more effective on commercial pools where you have an operator who is there all day, every day. On a residential service route or for homeowners listening to this, I guess homeowners would have more time than a service pro, but it's really a function of time.
It takes time to dissolve soda ash and add it slow enough that it doesn't spike your LSI too fast. Because if you add soda ash, it just clouds up the water. And what's really happening there is you're introducing carbonate ions at a high pH. And so those carbonates are going to bind to calcium ions that are in the water.
And the high pH is going to convert bicarbonate ions into more carbonate ions. So it kind of happens both ways. It's similar chemistry at the surface of why plaster dust is created. So if you have hungry water filling a plaster surface, it pulls calcium hydroxide out of the surface. The high pH converts bicarbonate in the water into carbonate.
Boom, you get plaster dust or calcium carbonate. So what I'm getting at here is these are two very different products. I personally recommend sodium bicarbonate for residential pool pros. It's going to be a lot more effective for raising alkalinity. Uh, Not soda ash just because of the cloudiness problem. And then you don't want to have to have callbacks because you clouded up a pool. And again, if you were there all day and you could get it in slowly, it'd probably be okay. But soda ash is mainly used for raising the pH without making a huge difference on alkalinity, and so let's find out why.
[00:04:51] Alkalinity article by Kim Skinner (onBalance)
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Eric Knight-1: And I'm going to read this, um, th- this little segment here. I make no claim to it. Kim Skinner wrote it, and you are welcome to look at this, and it's all on poolhelp.com. So thank you, Kim, for writing this.
He says, "Sodium carbonate. A 1% solution of sodium carbonate, or soda ash, in distilled water has a pH of approximately 11.4. Because of this high pH condition, sodium carbonate will raise the pH of the water more significantly than will sodium bicarbonate. And just as with sodium bicarbonate, sodium carbonate will also more significantly raise the pH when a lower alkalinity level exists.
The alkalinity contribution. The alkalinity of water is a measurement of its capacity to neutralize acids." We've covered this on the show before. "And a measurement of alkalinity in water is generally expressed as its calcium carbonate equivalent." There are several ways to calculate the amount of contribution to alkalinity by sodium bicarbonate and sodium carbonate. The following is one example.
Sodium bicarbonate. In order to calculate the amount of alkalinity increase by the addition of sodium bicarbonate, we must know its calcium carbonate equivalent.
We know that the equivalent weight or mass of calcium carbonate has been assigned as one hundred, and the equivalent weight of sodium bicarbonate is one hundred and sixty-eight. By dividing calcium carbonate's equivalent weight, one hundred, by sodium bicarb's equivalent weight of one sixty-eight, we know that sodium bicarb is only 59.5 percent of the equivalent strength of calcium carbonate.
By determining the amount of alkalinity contributed by pure calcium carbonate, we will then be able to determine how much alkalinity is contributed by sodium bicarbonate.
All right, let me put that in English. If you dissolved calcium carbonate, the same stuff as plaster dust, scale, whatever, but when that's in solution, if you were to introduce that, let's just say it didn't come out of solution.
Let's say you introduce that. It will raise alkalinity more concentrated than sodium bicarbonate. Think about that. Sodium bicarbonate or baking soda, if you want to call it that, is only 59.5 percent of the alkalinity gain that you would get from calcium carbonate.
But realistically, we're not adding calcium carbonate. If you're trying to add calcium, you're adding calcium chloride to raise calcium hardness. Bicarb is a different chemical. So you don't just buy calcium carbonate in a bag or limestone. So just be aware of that.
And then it goes into the math. If you have twelve pounds of calcium carbonate divided by a million pounds of water, we would have twelve pounds per million pounds of water, also known as parts per million, as alkalinity as calcium carbonate.
Since water has an approximate weight of eight point three four pounds per gallon, and 10,000 gallons of water therefore weighs 83,400 pounds, this is one twelfth of a million pounds. So, one pound of calcium carbonate added to 10,000 gallons would make 12 parts per million alkalinity. But we then have to multiply that by the strength, knowing that sodium bicarbonate is only 59.5% the strength of calcium carbonate, multiply that and you get 7.14 parts per million of alkalinity per 10,000 gallons.
[00:07:51] Orenda Chemiculator's accuracy
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Eric Knight-1: So what I want to show you here is I got the Orenda calculator here. A lot of people don't know this exists. I'm going to go to the main menu, and we're going to switch calculators here. Instead of using the one you're all familiar with, uh, which is, you know, left to right, current readings on the left, desired readings on the right, we're going to go to the main menu.
We're going to go to Other Calculators, and we're going to click the Chemiculator. Now, if you've never used this, it's going to require you to log in. You should have a login by now. If not, it's free. Just put in your email address and, and go. We're going to keep it in US. We could make it metric if we wanted to, but I'm just going to add a chemical to increase total alkalinity, and I'm going to select at the bottom sodium bicarbonate.
Now, this is in 10,000 gallons. I could change that to my own pool, but for the sake of this article, he's saying, based on this, because it's 59.5% of calcium carbonate, one pound of sodium bicarbonate should add 7.14 parts per million of alkalinity in 10,000 gallons. Let's see if it does.
I'm just going to add one pound. Boom, 7.14 parts per million. So this is really good. If you're using any of the routing softwares that include the Orenda calculator in them, or you're using the Orenda calculator directly, you have this. All of the alkalinity doses are already precise. Let's take a look at soda ash.
We're going to go back up here. And as you can see when you read this, if you choose to, um, the math is all shown, which is kudos to Kim. He shows his work. But if you look at sodium carbonate, or again, soda ash, uh, the equivalent is one hundred and six compared to one hundred. So if you divide that, you actually find out that sodium carbonate or soda ash is 94.3 percent the strength of calcium carbonate.
Time out. For years, I knew that soda ash was a lot more concentrated for raising pH, but I made the incorrect assumption in some of my classes, and I'm, I'm fessing up to that now because I didn't know, that one for one, if you put in sodium carbonate, it would raise the alkalinity the same as sodium bicarbonate.
That's actually not the case, and I apologize for that, and the calculator is about to show it. If I add total alkalinity with soda ash and I go one pound, ah, it aligns with his math. Eleven point three two ppm. Here it is at the bottom, eleven point three two parts per million. So it is a little bit more concentrated.
The difference is when you add soda ash, it raises the pH much more rapidly, and so it's a lot more likely to force an LSI violation and cloud up your water. And then you got to look at costs, and, and that really depends on where you are in the country.
[00:10:26] Closing
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Eric Knight-1: So if I could summarize this, what I'm really excited about is, number one, the calculator works.
It's very precise regardless of which chemical you use. So that's the first good thing. The second thing is the purity is relative to dissolved calcium carbonate. Now, I knew that, but I didn't really understand why they did that. I think we had an episode on it before, but it kind of slipped my mind because it's not that important. We just need to know the dose based on the chemical we have.
The reason it is compared to calcium carbonate is because of that 100 molar weight. That's the easy math. So you can always divide by 100 and find out your purity very easily. And so that's why it is, because, uh, y- you know, there is a carbonate in calcium carbonate. So we're going to show calcium hardness as ppm calcium carbonate, and we're showing total alkalinity as ppm calcium carbonate.
That is a really good thing because what that does is it gives us a shared currency, so to speak. We're comparing apples to apples at that point. Even though they're different chemicals, they are one for one in parts per million. And so this concentration happens in the background.
You don't really need to know it. But I figured this would be good to answer the question that we got of why are alkalinity numbers represented as ppm calcium carbonate?
So I hope that answers your question. Feel free to read this article. I hope you do. It is quite amazing, but I'm really happy that our calculator does have this right.
I was confident that it did, but just to have that validation when you see the math behind it. Credit to Kim Skinner and On Balance and the Journal of the Swimming Pool and Spa Industry. Again, you can read this article on poolhelp.com, and I hope you do. So get out there, have a great season, and make sure that you are not overdosing these chemicals and you're adding them correctly.
If you have any questions, ruleyourpool@gmail.com. This is episode 198. Whew, we're approaching 200. And I have already reached out to Jarred and invited him, because the fans really want Jarred back. I have invited him to join me for episode 200. We don't know what we're going to cover yet, but that's not important.
What is important is he's going to be on episode 200. Thank you so much for still listening, and share this with your friends. Rule Your Pool is back. Take it easy.