Bob Lowry on Pool Service Rookie Mistakes

Algae every week even though the test kit shows plenty of chlorine? That headache usually isn’t bad luck, it’s bad math. We dig into the most common rookie mistakes new pool service pros make and show the chemistry behind why a pool can read “sanitized” while algae still wins. The big unlock is understanding cyanuric acid (CYA) and how it binds most of the chlorine in the water, leaving only a small active portion available to kill algae. 

From there, we make the fix practical: stop guessing and start targeting free chlorine based on your stabilizer level. We walk through the easy field rule that free chlorine should sit around 7.5% of CYA, plus how adding borates at about 50 ppm can lower that requirement to roughly 5% in many pools. If you’re servicing trichlor pools with high CYA, this framework explains exactly why “6 ppm is high” can still be nowhere near enough. 

We also shift from pure chemistry to water balance and operations. We talk about the Langelier Saturation Index (LSI), what it’s designed to predict (scale forming vs corrosive water), and why “balanced” isn’t the same as “stable” when alkalinity and pH are constantly drifting. Then we hit a nuts-and-bolts issue that ruins otherwise good chemistry: filtration runtime. We explain turnovers, why one turnover only filters about 65%, why three turnovers is a smart target, and how low circulation creates dead zones where algae can grow. 

If you want to tighten up your pool maintenance results, reduce call-backs, and run a more predictable pool service business, listen through and take notes. For more training, visit swimmingpoollearning.com and check out PoolGuyCoaching.com, then subscribe, share the show with a tech who needs it, and leave a review so more service pros can find it.

We break down the most common rookie mistakes that keep new pool service pros stuck in recurring algae, cloudy water, and constant chemical chasing. We show how to set smarter chlorine targets using the cyanuric acid ratio, when borates change the math, why LSI can mislead if you ignore stability, and how pump runtime and turnovers make or break circulation.  
• misunderstanding how high cyanuric acid weakens effective chlorine  
• using the 7.5% of CYA free chlorine target  
• lowering the chlorine requirement with 50 ppm borates  
• why “2 to 4 ppm chlorine” can fail for algae prevention  
• what LSI predicts and what it does not  
• choosing target ranges to make water stable week to week  
• calculating turnovers from pool volume and flow rate  
• why short runtimes create dead spots and let algae take hold  

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Transcript

SPEAKER_00 0:14

Hi, welcome to the Best of the Pool Bay Podcast Show. In this episode, Bob Larry's going to go over some common mistakes you make as a new Pool Service Pro. We'll call them rookie mistakes. He'll go over these in detail for you here. And of course, you're going to glean a lot of knowledge from what Bob Lowry has to say in today's episode. 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 swimming poollearning.com. Let's talk about some rookie mistakes out there. Now there's a lot of new people in the industry, or you may be an employee coming on to a pool

Rookie Mistakes Setup

SPEAKER_00 1:02

company, and we'll go over some of the top mistakes I think people make in the industry when they first start. And I think number one, and this is also happening even with the old school guys out there, is not understanding the effects of high cyaneric acid on chlorine. And then on the second part of that, you know, how important the cyaneric acid and free chlorine ratios are, and something that a lot of people don't consider. And so they'll have a trichlor pool that has cyaneric acid of maybe 150 or 200, and they're getting algae in there every week, and the free chlorine levels at you know five or six parts per million, and they're scratching their head thinking, hey, there's tons of chlorine in here. Why am I still getting algae in this pool? So you want to go over kind of this misunderstanding that happens out there?

SPEAKER_01 1:51

For years we used to just put in two to four parts per million

Why High CYA Breaks Chlorine

SPEAKER_01 1:56

of chlorine in the pool, and that was supposed to be enough. And then every summer we all battled algae and put in algicides and superchlorinate and shock once a week and all those kinds of things. And and we were doing stuff weekly to bring the chlorine level up to where it would kill the algae. We started figuring out what the problem is. And and about eight or nine years ago, I spent a few hundred hours studying what's what's going on in the pool. And the good news is that because I'm independently wealthy and independent, if I want to spend 200 hours doing something, I don't have a boss telling me I can't do that. So I studied it to find out what kills algae, how much chlorine we need. Depending on who you talk to, we need only between 0.3 and 0.5 parts per million of HOCL in the water. And the some people disagree with the 0.3. I mean 0.03, but everybody would agree that that 0.05 parts per million HOCL will kill algae. So if we know that, then we're able to calculate how much chlorine is in the water if we know how much cyanuric acid is in the water. So we started figuring out how much cyanuric acid, how much chlorine is in the water. And the fact of the matter is, even with only 30 parts per million of cyanuric acid in the water, 97% of all the chlorine that's in the pool is bound to cyanuric acid. It's attached to it. And it's not like it's not available, but it's not available right now. Only the 3% that is not bound to the cyanuric acid is available for killing anything. That is an equilibrium reaction, 97% and 3%. So if you use some of the 3%, some of the 97 will switch over so that that 97 and 3% is maintained. But because we know that 3% of the chlorine is doing the work, we can multiply the 3% of the amount of chlorine that's in the pool and find out if we've got enough chlorine. So if you have say two parts per million of chlorine in the pool, if you multiply two parts per million of chlorine by 0.03%, okay, you and you well, let me back up. You also may know that when chlorine is in water, the pH determines how much HOCL is made and how much OCL is made. And the the OCL minus and the HOCL are at 7.5 pH is about 50%. So you got 50% HOCL and 50% OCL minus. So that means that only 1.5% of the chlorine that's in the water is gonna kill anything. So if we take two parts per million and multiply it times one point five percent, we get zero point three parts per million HLCl. And we said we needed zero point five. So if you're keeping the chlorine level at two parts per million in that pool, you don't have enough chlorine to keep algae from growing. And it is that simple. And if we put in three parts per million of chlorine in that pool, 1.5 percent of three is 0.45. That's not quite 0.5, but it's close. So three parts per million might actually work. It's on the maybe on the borderline. And if you multiply four parts per million times 1.5 percent, you have 0.06. And 0.06 will definitely kill algae. So what I claim in my most of the things I write, two to four parts per million of chlorine that's recommended by PHTA may not always work. And don't believe that if your chlorine level is between two and four, you're good. Because I just showed you that you could have two and not be good and four and be good. So if you're in between there, it doesn't mean you're okay. So instead of having to do the math that way, we reversed it and made it easier for you to calculate. And so the free chlorine level that you need in the pool needs to be 7.5% of the cyanuric acid level. And yes, that means if you've got a hundred parts per million of cyanuric acid in the water, you need 7.5 parts per million of free chlorine. It means that. That's their rule, and actually their rule actually never considered the fact

The 7.5% Rule And Borates

SPEAKER_01 8:01

that you would have cyanuric acid in the pool. Because your exposure to chlorine is less with cyanuric acid than without it. For that same reason, only three percent of the chlorine is available. So you're not exposed to four parts per million of chlorine, you're only exposed to three percent of four parts per million of chlorine. So the thing that you can do to reduce the 7.5 percent is if you add borate to the pool at 50 parts per million, you can lower the 7.5% requirement to five percent. And that becomes a much more manageable and easy number. 5% of whatever your cyanuric acid is is how much chlorine you need in the pool to prevent algae. And if it goes below that, then you you run the chance of getting algae. And and we have we've been teaching that for three years. I've written about it now for eight years, and I've also got a book that most of you have probably heard of called Pool Chemistry for Service Pros. And it's a short book of 28 pages, but we recommend in there to keep the level of borate at 50 parts per million and chlorine level at 5% of that of CYA. But that book has now been distributed to 13,000 service techs, and they're doing it, and it's working for them.

SPEAKER_00 9:40

Yeah, and I would say from field testing and experience, you know, if you want to keep your pool algae-free, even with a high chlorine level, like I gave that example at the beginning, a 200 parts per million cyaneric acid pool, not unheard of in California, by the way, a six parts per million chlorine is not enough to keep the algae out, even with borates in there. So um, with the borates, you would need 10 parts per million. So if if the new guy is struggling with algae pools and he thinks he thinks that, and this chlorine level is off the charts, you know, but I'm still getting algae, that's the reason because they don't understand the formula that you just went over there in great detail, by the way, which I really appreciate that. I like the fact that you reversed it because doing the math forward is difficult for anybody, and using that easy percentage backwards is much better. And then another aspect is the LSI. Interesting, I was talking to Scott Hamilton over at United Chemical about his Hamilton index, and that's another index that you can actually use that one in California pretty effectively because of our high calcium hardness level. But the LSI is pretty much the standard of the industry across the country. And what about the pool guy that probably has never heard of the LSI, never w never thought about it? What would be the problem with someone starting out their pool service business or working for someone and not even knowing what the LSI is It actually depends if he if he got one of our books and started using targets, he

LSI Basics And Why It Matters

SPEAKER_00 11:19

probably wouldn't need the LSI.

SPEAKER_01 11:21

But if he just started doing pools and he's got all this mishmash of information, understand that the LSI is a method of predicting whether your pool is going to be scale forming, whether you pool water is going to be scale forming or corrosive or what we say is balanced. And it's a method of predicting whether that will whether the water will be that way. And you measure, in the old days, we measured five things and plugged those test results into an equation and got the answer. And now with the advent of cyanuric acid and borate, we now have seven things to check. We most of the time look up the seven water tests, we look up a factor for each one of those test results and enter them into an equation. And the the desired result is to come up with a 0.0 answer. And that means your water is perfectly balanced, neither scale forming nor corrosive. It is important if you're going to be maintaining water to know if you're going to be forming scale or or not. And there are various indices out there, and frankly, the Hamilton Index is not an index. They call it an index, but it's not an index. And it pretty much does only work in California and Arizona. Most of the other countries can't use it. But and if you if you use the Hamilton Index and use some numbers from it's index and plug them into the LSI, you find that it's not balanced water. So I'm not a big fan of the Hamilton Index, although it's been around for a long time. But just because it's been around doesn't mean it's a great index. But in any case, if you want to follow it, it's better than not doing anything. So I would suggest just using targets as we recommend for everything. And then you really don't need to be using any index. You're just everything is on target or it's not. And if you don't put it on target, you're gonna have a problem.

SPEAKER_00 13:50

Yeah, it makes sense. And I I think that that's a good answer because your target ranges, and I'm you know, more and the more and more I look at it, and I use this example with you. If you go into the bank and you tell a teller, you know, I like to get $100 out, and she says, Well, here's 80, you know, it's within range of a hundred, you're gonna walk out of the bank not quite as happy. And so the targets make a lot of sense because you're talking about you know, a hundred thousand, two hundred thousand dollar investment in some people's backyards with their pool, and you have all these ranges, and you mentioned before in a different recording that if the LSI is could be perfectly balanced in those kind of ranges that people are using, you know, 80 to 120 for alkalinity, pH of 7.4, and it may not even be balanced.

SPEAKER_01 14:37

Well, you can balance the water so that it you have a perfect LSI, but still not have a stable pool. And that that is the problem. And you could, you know, you could balance a pool. For instance, if you had an alkalinity of 140, you could maybe use a a pH of 7.2 with that and and have everything else in the normal ranges, and you'd have a balanced pool. But with an alkalinity of 140 and a pH of 7.2, that's only gonna stay 7.2 for you know, maybe today. You know, tomorrow the pH is gonna be 7.5 or 7.6 or 7.8. An alkalinity of 140 is gonna raise that pH like crazy. So

Balanced Versus Stable Water

SPEAKER_01 15:25

there's a difference between balancing the pool and making it stable. And the goal is to make it stable so that from one week to the next or one visit to the next, nothing changes, or it changes just a little bit.

SPEAKER_00 15:42

Yeah, makes perfect sense. Another thing that we've touched on before is, you know, homeowners may not know this because they always are trying to cut their runtime down on their pool filter. That's one of the problems I have out there, is they're always telling me, I just had a customer yesterday tell me, Oh, can you reset my system so it's not running so long because my electricity bill was super high. But I think runtime of runtime of the pool filtration system is one thing that new people don't really pay attention to. You know, they may get an account where the customer has a 20,000 gallon pool running for four hours a day and they're scratching their head, you know, why is the pool cloudy? Why is there algae? So the runtime is a big deal, especially in the season.

SPEAKER_01 16:24

Yeah, it you know, the the fact of the matter is that that from a filtration standpoint,

Filtration Runtime And Turnovers

SPEAKER_01 16:33

if if you get one turnover of the pool, and a turnover is an amount of water that's equal to the volume that's in the pool gone through the filter. So, and so it's based on water flow. So if you take the the gallons in the pool and divide it by the flow rate, then you will find out what your turnover is in minutes, assuming that your pump is in gallons per minute. So you can determine how many minutes or hours it is to get one turnover. But from a a filtration standpoint, one turnover will only give you about 65% filtration. And then if you get two turnovers, it will give you about 85% filtration, and three turnovers will get you about ninety-two to ninety-five percent, and four turnovers will get you ninety-eight or ninety-nine percent. So, what we recommend is that you get three turnovers because the difference between three turnovers and four turnovers is like three percent, it's not worth doing, but you need to get three turnovers in your pool, and you can calculate for yourself how many minutes that's gonna be, and all you need to know is the flow rate. And so you put a a rotameter or flow valve right after the pump, right out, I'm sorry, at least after the pump and and before it gets back to the pool to find out what your flow rate is, and and then all you have to do is do the math. You know, if you got 20 gallons or 30 gallons a minute running through there, you got a 15,000 gallon pool. How many minutes is that? You know, it's 500 minutes to get one turnover. And and 500 minutes is uh almost eight hours. You know, so so and if you want three turnovers, it's 24 hours. So if you if you only run your pump at 30 gallons a minute for four hours, that's not even one turnover. That's a half a turnover. So you can't possibly get get enough filtration to to have a great looking pool. The other thing is, if the if you only run your pump for four hours a day, that means for 20 hours a day, there's no circulation. And and if you have a biomass, a biofilm, or an algae starting to grow someplace, it the that mass, that biomass uses up the chlorine that's in the vicinity. And if the circulation pump's not on, it used up all the chlorine. Now it can grow like crazy because there's no new sanitizer being brought to that area of the pool because there's no circulation.

SPEAKER_00 19:57

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