Eric and Jarred dive deep on calcium phosphate scale, aka hydroxylapatite, and how it differs from calcium carbonate.
00:00 - Introduction
02:15 - Credit to whom it is owed
03:14 - What is calcium phosphate?
08:42 - Formula for calcium phosphate precipitation
14:34 - Lab results (thanks Que Hales!)
16:05 - How to identify and prevent calcium phosphate scale
19:43 - Closing
158. Calcium Phosphate Scale
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[00:00:00] Eric Knight: This is the episode that in some respects I have been dreading, but I've also been looking forward to talking about this for, and I'm not exaggerating, over two years. It is a complex topic and I have Jarred on here who knows absolutely nothing about this topic because he has not done any research for it. Jarred, good to have you back.
[00:00:19] Jarred Morgan: I am happy to be back. And honestly, this was one of those, you know, I think I saw an article that you wrote that I was supposed to proofread that I didn't proofread because I don't like reading your stuff. Especially show notes. And
[00:00:34] Eric Knight: There are none for this. Don't worry about it.
[00:00:36] Jarred Morgan: Good. Cause I'm just going to just put it out there. I know absolutely nothing about what you're about to speak of, so we can go.
[00:00:43] Eric Knight: In fairness, you were not my first or second pick to be the guest on this topic. I had two other people that were just harder to get. But that's okay. That's okay. Nobody's perfect. In this episode 158, we are going to talk about calcium phosphate.
[00:01:00] Jarred Morgan: Ooh, riveting.
[00:01:01] Eric Knight: specifically calcium phosphate scale. And Jarred, in all the years that I've worked at Orenda, we have heard about this a lot, haven't we?
[00:01:09] Jarred Morgan: I have heard about this. And some of the explanations or processes that we've heard are pretty, pretty wrong. Let's just say that.
[00:01:19] Eric Knight: Oh, they're way wrong. And now that I've done multiple months of researching this, there's not that much information on what's in swimming pools, but there is tons of information on calcium phosphate out there because it's critical to biology. It's what our bones are made of. It's what our teeth are made of. And it's how you can do bone grafts. And there's just tons of medical research on this stuff. But almost nothing on the types that we get in swimming pools. So that's what we're going to unpack in this episode and giving credit to where it's due. We will name our sources as we go. Episode 158. Let's go.
Credit to whom it is owed
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[00:02:15] Eric Knight: Before getting into this, we could not have done this episode without some help. I reached out to over a dozen material scientists and chemistry firms and just anything that I saw, I would read peer reviewed articles. And then I would like go on LinkedIn and find the authors and just shoot them an email.
[00:02:33] And it took a very long time to hear back from any of them. And I want to thank them for their help on this. They did not have to help. The pool business is not their concern. Some of them are medical doctors. Also in particular in the pool business two people translating this into swimming pools so that it's relevant for you. Those two people are Que Hales from OnBalance, and Richard Falk. And we cite Richard all the time because he is a chemist who can explain just about anything. And he was extremely helpful in this once I figured out what was in those tests and I only knew what was in a swimming pool thanks to Que. Que so graciously shared chemistry results from samples that he had extracted from a pool heater. And without that, I would have been blind.
What is calcium phosphate?
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[00:03:14] Eric Knight: Because here's the reality. Calcium phosphate is a broad term to talk about a whole bunch of mineral ion pairs that contain both calcium and some form of phosphate. I'm going to rattle them off, not that you need to remember it, but to give you an idea of how many there are, there's a group called apatite. All right, that's Ca5(PO4)3.
[00:03:37] If you're on the website, when you read the article, it's all written there. Hydroxylapatite, also called hydroxyapatite, chlorapatite, fluorapatite, tetracalcium phosphate, monocalcium phosphate anhydrous, monocalcium phosphate monohydrate, dicalcium phosphate, dicalcium phosphate dihydrate, dicalcium phosphate monohydrate, dicalcium diphosphate, calcium triphosphate, tricalcium phosphate octacalcium pho.
[00:03:58] You get the point. It goes on and on and on and on. And when we think about ion pairs, we think of usually calcium carbonate. So you have a mineral with two protons on it. That's called a cation. And it is pretty unstable. It is looking for something to bind to.
[00:04:14] So it looks for an anion. Well, carbonate is the most convenient because it's Ca--. And this is what the LSI is based on, but the LSI has nothing to do with calcium phosphate. It has nothing to do with calcium sulfate either.
[00:04:28] That's another ion pair. Calcium phosphate, in relation to the swimming pool, is usually going to be one of two different forms, but the most common from what we can tell based on the study is calcium It's going to be something called hydroxylapatite. That's what was found in the heater of the test that Que Hales gave me. And judging by Jarred's face, he's already asleep.
[00:04:49] Are you snoring over there?
[00:04:51] Jarred Morgan: There was a few things here that I, I'm just going to sympathize with our audience for just a second.
[00:04:56] Eric Knight: Yeah. No, you don't have to remember it.
[00:04:58] Jarred Morgan: There's very important things that stood out to me.
[00:05:01] Eric Knight: Like?
[00:05:01] Jarred Morgan: Number one, I think you blacked out. You just riffed. Uh, number two, I did fall asleep momentarily. Number three, you said cation and all I could think about was Blue, my cat. And that's about all I absorbed from what you just said.
[00:05:17] Eric Knight: Good. Good. Yeah. That was my goal. Thanks for that.
[00:05:20] Jarred Morgan: Now, if we get any questions revolving around this topic, please direct all of them to Eric.
[00:05:26] Eric Knight: No, send them to Jarred. He is now an expert. Here's the point...
[00:05:29] Jarred Morgan: Because if you send it, I'm going to send it directly to Eric.
[00:05:33] Eric Knight: Okay. I'm reading from the article, you can see all this in there. We're publishing a blog called understanding calcium phosphate. These groups, when they form, are harder than calcium carbonate. In some respects, depending on how you measure concrete, they can be harder than concrete.
[00:05:50] You can use the Mohs hardness scale or the absolute hardness scale, we cover this in the article. If you have calcium phosphate scale, it is really, really hard to remove. It is not a soft substance. Whereas you can take calcium flakes from a saltwater pool, which is calcium carbonate, and you can almost dissolve them in your fingers, right?
[00:06:08] You can just kind of smash them into dust. Scale will harden though. That's also calcium carbonate. Calcite crystals, also calcium carbonate. And what that means is, the structure of the substance determines its hardness. I'll give you an example. What is the difference between a lump of coal and a diamond?
[00:06:25] Massive difference in strength and hardness, but it's all pure carbon, right Jarred?
[00:06:31] Jarred Morgan: Pressure.
[00:06:32] Eric Knight: It's the alignment of all the bonds and everything. It's still the same substance. It's just a completely different structure. Well, that's the difference between calcite and normal scale, calcite and calcium flakes in saltwater pools. They're all calcium carbonate. Plaster dust, all that stuff, but they have different hardnesses.
Myths and misunderstandings about calcium phosphate
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[00:06:46] Jarred Morgan: Do we want to touch on the common things that we've heard in the past that people would ask us kind of regularly?
[00:06:54] Eric Knight: Go ahead. I was going to get to that, but let's just go your way. You start. Ask the questions.
[00:06:59] Jarred Morgan: Well, you went into the science here, you dove real deep headfirst real fast.
[00:07:03] I wanted to get it out of the way.
[00:07:04] Yeah, the reason why we we bring this up is because we commonly get questions, or we have in the past, about adding phosphate removers to control scale in a salt
[00:07:15] Eric Knight: Yeah, flakes.
[00:07:16] Jarred Morgan: Or adding phosphate remover to stop heat exchangers from scaling up. I've heard of calcium phosphates building up in, uh, sand filters and being extremely hard. And not easy to remove. And people think, well, if I just use a phosphate remover, therefore it's going to stop calcium phosphate from forming and occurring. I don't know if that's true or not. Maybe your research says will.
[00:07:39] Eric Knight: So you're right about that. There is a prevailing belief in this industry, and it's still on one of our competitors websites. That if you have flakes in your saltwater pool, meaning your salt system is scaling up, that it's calcium phosphate. I have great news for you. There is a very, very, very, very, very low probability that that's the case. Because if it was calcium phosphate, you'd probably have to get a new salt cell. Good luck cleaning it.
[00:08:05] I mean, you could dissolve it with a high, like really, really high concentration of acid over a long time, but it's not easy. It does not just disappear like calcium carbonate does. It is not determined by the LSI like calcium carbonate is. There is an index formula that we have in the article to determine it's precipitation, just like we can determine scale forming water. But the numbers are so extreme to get this problem, you would have to have very, very high phosphate levels, high temperature, high calcium and a high pH to make it happen. And I'm going to go through some of those numbers.
Formula for calcium phosphate precipitation
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[00:08:42] You want to hear the numbers, Jarred? Or am I going to put you to sleep again?
[00:08:45] Jarred Morgan: I'd love to hear the numbers.
[00:08:46] Eric Knight: Okay. This formula originally comes from a study that was done in 1979, but it has been referenced in a whole bunch of descaling agents in industrial water treatment, like drinking water systems. Primarily cooling towers and wastewater. Big, big chemical companies have this information out there because it is a problem at very, very high temperatures. Particularly when you're in like cooling towers and power plant reactors and boilers. Because the temperature is so high, you're a lot more likely to have this there if you're using phosphate based sequestering agents. Which most drinking water does now ever since Flint, Michigan.
[00:09:20] But the temperatures that we're talking about in a boiler are reaching 212 degrees to boil water. Your pool heater isn't anywhere close to that. It might reach 150 and only for a few seconds as water passes through it. It's nothing like steam. So just keep that in mind that we're talking about completely different applications of water. The likelihood of you having this is very, very low. But we have seen it.
[00:09:46] But every time that we've seen it, it has either been in a very hot pool, usually a commercial pool on Cal Hypo with a filter and some form of either buffered acid or sequestering agent that contains high phosphates. The phosphates are through the nose is basically what I'm getting at. So here's an example of how much phosphate you need to precipitate this. And it is relative to calcium, your temperature, translated to Celsius, and the pH. All right.
[00:10:17] The formula goes, just read it on the site, but it's 10 to the power of 11.755, minus the log of your calcium hardness, minus two logs of your temperature, minus 0.65 times your pH actual. Everybody got all that? Cool.
[00:10:32] Let's do some real numbers of what that means. Let's take a pool, Jarred, that's 82 degrees in the summertime. Let's say in North Carolina where I live. 350 calcium hardness, .
[00:10:40] Jarred Morgan: Doesn't seem that high.
[00:10:41] Eric Knight: It's a little lower than I would have, but most pros were going to be in that area if they're following us, and an 8.0 pH. Which is very common if your pH ceiling is regulated. By the end of those seven days, it's probably going to be around there.
[00:10:53] Jarred Morgan: Very common numbers.
[00:10:55] Eric Knight: So I'm going to plug that into the formula. You would have to have 13.3 parts per million of phosphates. In other words, 13,300 parts per billion of phosphates.
[00:11:08] Jarred Morgan: Which is not crazy because it can happen.
[00:11:10] Eric Knight: Yes, but you also need it to stay at that temperature and you need time. It doesn't just happen in seconds. It starts to precipitate at that level. Now, the higher you go, the higher that saturation goes, the more it starts. But that's like, we're going to use the LSI for a second. It's starting to go purple at that level. Right?
[00:11:29] That's like your threshold where you start to get oversaturated. Of course, the higher you go, the more you're going to get. If you had this, you basically have to jackhammer it out. You can grind it off, you can jackhammer it out, but you're not going to be able to chemically remedy this easily at all. It is much easier to prevent it.
[00:11:48] Where we have seen this happen is in commercial pools. Commercial pools that are heated. Usually it's like a swim school or a therapy pool at an old folks home where they want the water, like 90 degrees or 88 or something like that.
[00:12:01] So let's give another example. 88 degree water. This time it's a Cal Hypo commercial pool, 700 calcium, which is very common with our commercial customers. 7.5 pH, because it's a commercial pool, they have an acid feeder. But in the cases that we've seen it, it was buffered acid that had phosphates in it. To those companies credits, apparently they have changed their formula. It's not buffered with phosphates anymore, supposedly. Um, and that's good news.
[00:12:27] But they use a sequestering agent because a lot of Cal Hypo has a phosphate based scale inhibitor in it so that the feeders don't scale up. This is very common. Long story short, here's the numbers. Remember, 88 degrees Fahrenheit, 700 calcium, 7.5 pH. You would need 11,240 parts per billion.
[00:12:48] It's a little lower than 13,000, right? But it's still pretty darn high.
[00:12:53] Jarred Morgan: Well, that's just because your calcium's higher in the temperature. So you're trading.
[00:12:57] Eric Knight: Calcium and temperature, but your pH is way lower, right? If the pH was 8.0, and this is where we get to a residential pool in a place like Tucson. If the water temperature is that high and the pH gets up to eight. Suddenly that number jumps way down. That number jumps down into the six or seven thousands.
[00:13:16] And if your pool is heated, for instance, it's probably going to deposit in a heater. It is very unlikely to deposit in a salt cell. We have never seen it happen. Ever. And we get calls about flakes... On the hotline is it every day multiple? I mean, we, I know we get them almost every day.
[00:13:33] Jarred Morgan: Yes.
[00:13:34] Eric Knight: And the comments we see on homeowner groups in Facebook and pro groups in Facebook. What are these flakes? What are these flakes? I keep getting them. People keep posting on Facebook that's calcium phosphate.
[00:13:44] Somebody very credible in the industry just posted it within a month too. Saying, Hey, that's calcium phosphate.
[00:13:49] Jarred Morgan: Again, common misperception.
[00:13:51] Eric Knight: Yeah, it's most likely not. We've never seen it and we have seen tons of flakes and we hear about them all the time. Calcium carbonate all day long is pretty much what it's going to be. And it's going to be localized problems too. But you're never really going to see calcium phosphate in a pool. You're not going to see it on your tile line. It's not nearly hot enough.
[00:14:08] Anyway. I digress. Like I said before, it's very hard to get out. So it tends to land in pool heaters. It tends to land in filters like sand filters that have to be jackhammered and cut open to change the media because it's like, harder than concrete at that point.
[00:14:24] Jarred Morgan: Do you think the silica or anything has anything to do with the sand filters being a common or not common? This isn't a common problem, everyone. So let's just start there. But obviously we've seen it in a sand filter.
Lab results (thanks Que Hales!)
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[00:14:34] Eric Knight: I don't know that the silica from the sand is reacting with it, but, um, I mean, it's possible. Because that gets me to the samples that Que Hales sent to a lab, and he shared that report. So full credit goes to Que on this one for this information.
[00:14:48] This calcium phosphate was not behaving like calcium carbonate. So they chipped it out of a heat exchanger and they sent it to the lab. The part that was touching the heat exchanger was high concentration of copper oxides. Which makes sense because it's degrading the inside of the heat exchanger, right?
[00:15:04] Jarred Morgan: Touching the copper heat exchanger. Yeah.
[00:15:06] Eric Knight: But the inside was a different color. And that was what was surprising. It was mostly colorless, a little slightly yellow. And it had very high concentrations of calcium and phosphorus. Imagine that. And the lab said, this looks like hydroxyapatite, which is that type of calcium phosphate we're talking about. And based on the chemistry, you have everything that you need in the pool. And that formula that we just spent minutes talking about to calculate how much phosphate it was, that's for hydroxyapatite. That's the saturation.
[00:15:37] Now that can be extrapolated to other forms of calcium phosphate. Why do all the other forms when we're talking about the one that has been proven to be in swimming pools? This stuff is really hard to remove. It takes a hammer and chisel and you have to break it out. It's not like calcium carbonate. You run muriatic acid on here. It doesn't really do much. Like it can if it's got enough time, but it's going to destroy everything around it. So you really just have to physically remove it.
How to identify and prevent calcium phosphate scale
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[00:16:05] Eric Knight: And it's not pure white. Okay. It's off-white. Whereas calcium carbonate is pure white. And I can look at the two and tell there's a difference between them just based on color alone.
[00:16:16] So if you do see something that's pure white and it dissolves and just fizzes away in muriatic acid, that's not calcium phosphate. Calcium phosphate does not do that, and that's a way that you can diagnose this at home. Chip out a little bit of it, carefully. Put it in some diluted muriatic acid, and if it fizzes and dissolves, that's calcium carbonate. And that's good news for you because it means we can treat it and we could probably get rid of it with SC-1000 and some LSI balance and it'll go away.
[00:16:44] Calcium phosphate is not so simple. But it is very easy to prevent. What we need to do is we need to make sure that we don't have too much calcium, right? We like calcium, but we don't need too much. And we have to limit how high the pH goes, which goes right into our pH ceiling conversation. And finally remove phosphates. So if you just follow Pillars One and Three of the Four Pillars...
[00:17:08] Jarred Morgan: And if you really want to be an overachiever, just put a chiller on your pool.
[00:17:13] Eric Knight: Yeah, you can put a chiller on your pool. If you're trying to. That kind of goes against what they're trying to do with heaters in commercial pools.
[00:17:19] Jarred Morgan: Sorry.
[00:17:20] Eric Knight: Yeah. But
[00:17:21] Jarred Morgan: Just trying to promote industry, uh, movement forward, okay?
[00:17:23] Eric Knight: Fair enough. Fair enough. If you keep your phosphate levels low, and it, you know, we recommend under 500 for other reasons. And you can learn about that in Pillar Three, if you go through our Four Pillars. But if you're doing that, you're never going to have this issue. It's like mathematically impossible unless your calcium was like 20,000, which is not going to happen. You'd be way in violation of the LSI anyway. If you're LSI balanced, generally speaking, your calcium is not going to be too extreme, or your pH. And all you really have to do is manage your phosphates. And that's very easy to do.
[00:17:56] Jarred Morgan: It is easy to do, but some of that is people that don't pay attention to what they're applying to their water, right? We've talked about this before, I don't know how many times, countless. But a common scale or metal removing chemical is phosphate based, and that goes into a lot of these chemicals that we put into our water. SC-1000 does not, but it is a very common chemical that is used.
[00:18:18] Eric Knight: And they work.
[00:18:19] Jarred Morgan: Yeah They do work obviously, and HASA, we sell a, it's not a strictly phosphate, but there's some phosphates in it, but it's really good at removing metals and stains, things like that. You just have to know how to remedy these problems after the fact. What are the byproducts that are associated with them? And how do you attack them afterwards?
[00:18:36] Because with a common scale remover or metal removing product in industry, if you open and close a pool, and you apply the recommended dose, it is not uncommon to spike your phosphate levels well over 3000, 4,000 parts doing a treatment like that. And if you do this multiple times without doing a phosphate treatment or draining or diluting your water and so forth, you can get those levels very high.
[00:18:58] Eric Knight: You're absolutely right. Most of those sequestering agents are going to be phosphate compounds that are not readily available to create this yet. But in sunlight or oxidation over time, they will break down into orthophosphates. And that's what is going to bind into this stuff to create calcium phosphate. So at first, it can actually help because it's going to bind up calcium and sequester it.
[00:19:19] Jarred Morgan: Which is why it works.
[00:19:20] Eric Knight: Yeah, temporarily, right? But if you use it over time and eventually you get enough of this saturation stuff, you get the point.
[00:19:27] And that ties into the last thing you could do for prevention. You can use something like SC-1000. We don't like pushing products on the podcast, but if you chelate your calcium, it will not bind to this. That chelated calcium is spoken for. So you'd have to be way out of balance.
Closing
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[00:19:43] Eric Knight: So I guess our message here, Jarred, is this is a rare problem. Most people do not have to be concerned with this. It just pains me to see people trying to fix a problem like flakes in a saltwater pool is usually the main one by putting a phosphate remover in and then getting frustrated that it didn't fix the problem.
[00:20:00] Well, first of all, we make a phosphate remover. You would think that I'd say, yeah, yeah, yeah, keep, keep, keep buying PR-10,000. But that's not going to solve your problem. That's the reality. That's not your issue. And while there is a potential chance that you could have it, you'd have to be so far out of bounds on phosphates for that to even be a consideration that it's just unlikely.
[00:20:22] If you follow Pillar 3, you should never have this concern. And prevention is way easier than remediation. Because if you have this stuff, ho ho ho, good luck. You're going to have to do a lot of work to fix it.
[00:20:34] So, stay ahead of it. Nobody wants to replace an entire filter. Or pump. Or all the plumbing in between. Because this stuff forms pretty much everywhere, if it precipitates out. Nobody wants to deal with that. That's expensive. A ounce of prevention is worth a pound of cure.
[00:20:50] Jarred Morgan: Yeah, basically what we preach all the time. Be proactive. Understand what you're doing, understand what you're putting in.
[00:20:56] Eric Knight: Now, Jarred, have you awakened since the first two minutes when I went through the science? Are you back with us now? Or was this all like a daydream?
[00:21:03] Jarred Morgan: No, no, I feel like I'm engaged now. I got a good nap, I just do what I can when I can.
[00:21:07] Eric Knight: Well, I can get behind that. This has been episode 158 of the Rule Your Pool podcast. The feedback that we are continuing to get from your customers means the world to me.
[00:21:16] It's just been great that people are gleaning value from this. And so we're going to keep doing it. It's just a lot of work. Especially right now with the heavy travel. So please be patient with us as we get this information out to you.
[00:21:28] It's not like we can just make this stuff up and come out with an article of this depth overnight. It took months to find all of this information and to speak to experts. And I want to thank them again, especially to Que Hales for sharing the research with us. And to Richard Falk for helping us understand what it all means and what these formulas actually mean.
[00:21:47] We could not have done it without you guys. And we hope that it brings value to the industry and that's what they want as well. So speaking on their behalf, they did it for you. And that's the point. They didn't do it for me. They did it for you. We do this for you as well. Thank you all. If you have any questions, ask.orendatech.Com. Hopefully it's in the help center. And if it's not, you can submit a question at the top. Jarred, anything else?
[00:22:10] Jarred Morgan: Nothing to add here. Appreciate the, uh, opportunity to come back and be a cohost. um, I'll try to make it a little more regularly, but no promises.
[00:22:20] Eric Knight: All right. Take care, everyone. Thanks.
[00:22:22]