Mythbusters: Pool Chlorine Edition

Ever wonder why a pool stays clear for months and then collapses in a heatwave despite “weekly shock”? We pull back the curtain on the most persistent pool chemistry myths and replace them with simple, durable rules you can use on every visit. This is a frank guide to working with stabilizer, choosing the right chlorine, and avoiding the subtle traps that turn easy weeks into green emergencies.

We start by dismantling the calendar-based approach to shocking. Chlorine demand isn’t a date on your route sheet; it’s a relationship with cyanuric acid. Using the 7.5% FC-to-CYA guideline, we show how to set smart targets, when breakpoint chlorination makes sense, and how to avoid dumping gallons that don’t move the needle. From there, we explain why trichlor, liquid chlorine, and cal hypo are not interchangeable. Each has a job, a byproduct, and a best-use scenario—understanding that is the difference between controlled, predictable water and chasing problems.

High CYA gets a hard look. Yes, some techs maintain clear water at 150 to 200 ppm CYA, but they pay for it with higher chlorine demand and slower kill rates. We outline practical ways to cap stabilizer—dilution plans, mixed dosing strategies, and seasonal resets—so you’re not stacking tablets all summer. We also revisit the old habit of weekly algaecide and how modern enhancers like borates and phosphate enzyme blends can help without becoming crutches. The priority remains constant: solid FC/CYA targets, clean filtration, good circulation, and consistent brushing.

• weekly shock myth versus measured breakpoint
• FC targets tied to CYA at 7.5 percent
• trichlor, liquid, and cal hypo roles and byproducts
• high CYA management, limits, and dilution strategy
• algaecides versus enhancers and prevention basics
• saltwater generators as continuous chlorine supply
• testing, filtration, and circulation as first principles

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Chapters

• 0:00 Welcome And Coaching Invite
• 2:33 The Weekly Shock Myth
• 5:38 Chlorine Levels And CYA Basics
• 8:44 Not All Chlorine Is The Same
• 12:19 High CYA: What Works And What Breaks
• 17:19 Algaecides, Enhancers, And Real Prevention

Transcript

SPEAKER_00: 1:02

Hey, welcome to the Pool Bay Podcast Show. In this episode, I'm gonna cover some common myths that you may believe. A lot of pool pros still think this way, and some of these myths about pool chemistry, I think should have been debunked a long time ago, but of course, it's hard to kind of fix something that's kind of been believed over time in the industry. 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. I'll start with this one, and this is one of the things that I often hear out there when pool companies hire people, and this is something that is a practice that was, I think, more prevalent than it is now because of the cost of chemicals. But you would always tell your pool techs that are starting out in your business that you want to shock the pool weekly. There is this company here in my area, and I know a pool tech that worked for them, and the order had them pour in two gallons of liquid chlorine every week. No matter what the chlorine level was in the pool, he would just have them just pour this in. And he would, of course, order from Hosta directly, have it delivered to the property. So the pool techs had a full truck of liquid chlorine all the time. I thought this was odd that he would have this mandate of just shocking the pool every week. And this is something that a myth that I think is in the industry still, where in the summer you have to shock the pool every week. And of course, the truth is, yes, some pools do need shocking when the chlorine level drops below the level that you should be maintaining it at. Now, I could talk the whole podcast on what chlorine level the pool should have. I'm just gonna say that you want to factor in cyaneric acid and your baseline chlorine level based on the amount of cyaneric acid in the pool. And I'll just use Bob Lowry's formula. This, of course, is actually a minimum in the formula, which is your free chlorine level should be 7.5% of your cyaneric acid level. So if your cyaneric acid level in the pool is 100 parts per million, your free chlorine level daily should be 7.5 parts per million. If the cyaneric acid is less, of course, then you would have less free chlorine. And so, yes, if it does fall below the baseline chlorine level for that pool, you will need the shock to pool. However, you know, like I was mentioning, telling employees to pour in two gallons of liquid chlorine, no matter what the level is, is not logical. You're just wasting product, and it's not something that's going to be beneficial to the pool. Now, you want to, of course, check the free chlorine level and make sure that it's at that level, then you would add shock to the pool if necessary. And shocking, of course, is another thing that you have to kind of measure because there's different levels of shock. You can raise it to 10 parts per million, 20 parts per million, 30 parts per million. And if you have some combined chlorine, you're trying to get to the break point of that. So there's all kinds of aspects of shocking. So I think one of the myths is that you can just shock a pool in the summer and that helps maintain it. When in fact, there's a lot of layers to this, there's a lot of different products you can use to bring the coin level up. There's a lot of different shock levels that the pool needs, and it's not just something that you can just say, well, if you shock the pool every week, you're gonna be fine. That's definitely a myth, and reality is balancing the pool is important, and calculating the shock level is also a big factor in this equation. Here's another one that I often hear is that all chlorine types are basically the same, they're a sanitizer, and so there really isn't any difference if you're gonna use cal hypo over liquid chlorine or if you're gonna use trichlor tablets. And I think the easy answer is of course they're all different because the manufacturers sell different chlorine products for different situations and different usage. For example, the trichlor tablets have probably the most concentrated amount of chlorine, but they're not used for shocking the pool because you can't just add you know four tablets to the floater if the pool has zero chlorine and expected to bring it to the shock level rapidly. And of course, you have your calhypo and your liquid chlorine, which are used more primarily for raising the chlorine level up rapidly in the pool. You can also use that to maintain the chlorine level. However, you're going to lose some parts per million per week, and since both the liquid chlorine and calhypo have no stabilizer, no cyaneric acid, and the reason why the trichloride tablets last so long and are for weekly chlorine dosing is that they dissolve slowly, they have cyaneric acid in them, and they're ideal for that particular usage. So they're not the same with any respect, and the strength is all different, and it's really one of those things when you're starting out an industry, you probably think that they're all the same. Like when you go buy milk at the grocery store, you have vitamin D milk, whole milk, then you have 1%, 2% skim milk. I'm not a big milk person, but I think there's probably more different milks out there, but it's still a dairy product, milk product from a cow, so they're all the same. But in pool service, all the chlorine types are actually very different from themselves. They all have different byproducts, they all have different reasons you're using them. So you can't just say in a blanket statement that all chlorine is the same, you can use whatever in the pool and you'll be fine. I think that's something that you learn as you start to kind of disseminate which chlorine type is best for your pool service use or personal backyard pool use, and which one is not as beneficial. And just briefly, I could just say that if you just use trichlor tablets as your primary sanitizer in the pool, if your area doesn't get like 30 or 40 inches of rain during the rainy season or you don't partially drain the pool, you're gonna add a lot of cyaneric acid to the pool, which makes things more difficult to maintain. So that's one of the drawbacks. And I would say cal hypo and liquid chlorine, cal hypo the byproduct is calcium, liquid chlorine is salt. So those byproducts are a little less harmful to the pool, but everything has a byproduct in nature, everything has a byproduct in chemistry, and so the chlorine types all have different byproducts, they all have different strengths, and they all have different usage. Here's one where you're gonna get a variety of answers depending on who you talk to in the industry, and this is you can't have too much CYA or stabilizer or cyaneric acid in a pool. Now, there are many people out there that believe that you can maintain a pool properly with very high cyaneric acid, and the truth is you can. You can load up your pool with tablets and have the cyaneric acid at 200 parts per million in the summer, and you can maintain that pool by just adding more and more chlorine to the pool. And this is something that a lot of companies do out there. A lot of people purchase pool routes and they realize that man, this this person had the cyaneric acid at like 250 in every pool, and the pool was maintained pretty well. So there is an argument on one side that stabilizer level doesn't matter. However, there is rules and there are regulations. Like, for example, in commercial pools here in Los Angeles County, you cannot have more than 100 parts per million of cyanaric acid in the water because the higher the cyanaric acid level I mentioned earlier, the higher the free chlorine level needs to be. And the somewhat less effective that chlorine is at the higher cyanaric acid level in the pool, the kill rate is reduced pretty dramatically. The kill rate of viruses and bacteria is reduced dramatically. That's why the LA County has these regulations where you can't have too much cyaneric acid in the water, but you can easily maintain the pool with high cyanuric acid during the summer. It's not something that cannot be done. But there are certain pools with high cyanuric acid that are very difficult in the summer, and so it's one of those things where it's you can do it, but at the same time you can't do it on certain accounts, if that makes sense. And believe me, the old school pool guys never really worried about cyaneric acid levels because they would just keep the free chlorine level high by adding more and more tablets. You start the season adding two tablets, and then the next month you're adding three, and by near the mid or end of summer, you're adding four or five tablets to a pool to maintain that chlorine level, and then of course the cyaneric acid level is increasing dramatically. And again, if you don't get a lot of rain in your area, I would say 30 to 40 inches is probably ideal to dilute that pool, or if you don't do a partial drain of the pool, you're gonna have a lot of cyaneric acid in that pool through the winter and then into the next season. So I'm gonna say that the better way is to use a combo approach with your pools with trichlor tablets and then liquid chlorine and calhypo to bring the chlorine level up, so you're not overusing trichlor tablets and you're not adding you know a ton of cyanaric acid to the pool. So there is a little bit of truth in this myth. You can do it, but eventually you're gonna hit a wall with these pools that have these really high cyanaric acid if the water is not being diluted in some fashion or some way. Here's one that I think has kind of gone away mostly, but the old timers and when I was trained, I was always taught to put in a weekly algicide to the pool. You know, you would just put in you know one ounce of sodium bromide in the pool, you would use a polyquat squirted in the pool, or you can use even a copper algecide. The thing is that the algees, the thinking behind that I should say, is that adding just a maintenance of an algicide will prevent the algae in the pool. And in some respects, this kind of myth has been kind of turned a little bit, and we do use enhancers in the pools now, like you can use a pool or x, which is basically like adding a weekly algicide to the pool. You can use borates to 50 parts a million, you can use a phosphate enzyme combination to help prevent algae from growing. So it is kind of like one of those safety nets that hasn't gone away. We just we just have kind of changed it now to where you're not adding a polyquat or sodium bromide or another algacyte in a maintenance dose every week, but you are adding enhancers to help prevent algae from forming in the pool. And I think the reason why this myth that you could you need to add it, you need these things, and and on in all honesty, if you sanitize the pool and maintain it at the proper chlorine level, you really don't need anything. But these enhancers are really helpful in the pool industry because we're at the pool once a week, and this is a great way to kind of prevent the pool from turning. If you're a homeowner and you're you can you know take care of your pool every day of the week, you probably don't need anything beyond checking the chlorine level, balancing the pool, and adding the sanitizer. But since we're servicing pools and multiple pools, by the way, you know, 70 or 80 pools a week, and the last thing we want to do is have a pool turn on us, spend 20 minutes brushing it, treating it for algae. So there is some logic behind this because you're trying to get through your day, and of course, you're doing more than one pool, you're doing 15 pools a day, and the last thing you want to do is to be battling algae. So it does make sense for pool service to have developed this myth that adding an algecide, a made in stose, is a great way to prevent algae, and there's a little bit of an insurance back there. And the enhancers are kind of like an evolution of this to a point where if you're not using enhancers, you're probably gonna be struggling out there in the summertime. And I think the actual myth part is that by doing the little algebra thing, you're gonna prevent algae in the pool, and you're ignoring a lot of other factors, you're ignoring the proper free chlorine level, you're ignoring clean filtration, all these other factors kind of just go on to the back burner, and just by putting a little algacyte in, you think you're gonna be fine. So I think this is a dangerous myth because you are not counting all the factors that go into balancing the pool and making sure the pool stays algae-free. So be careful thinking that adding an algicide is going to or even an enhancer is going to make things easy. You do have to balance the water and have to kind of think about the other factors that contribute to algae in a pool. Here's another one, and I just heard this the other day, which is kind of funny, and this is someone who was asking about you know a way to maintain the pool without chlorine, like using a salt water generator, and I find that to be funny in a way because the manufacturers and the salespeople did start out by kind of pushing these as kind of a chlorine alternative, and what they meant by that was you don't have to add chlorine to the pool with tablets, liquid chlorine, and cal hypo, but somehow it got translated that or kind of morphed into a saltwater pool is not a chlorine pool, and in fact, it is a little miniature chlorine factory that is producing kind of a pure chlorine into the pool. I'm kind of dating myself, but back in the day when I was doing pool service in the 90s, there were a lot of gas chlorine companies. They would have these canisters, and they would have a route where they would just I had some accounts actually that had gas chlorine service too. I wasn't doing it, but there was a glass gas chlorine company that was servicing the pool, and they would pull it back there. It was like a little three-minute stop for them basically, go back there, put the gas chlorine into the pool, and then head on their way out. And kind of very similar, the salt water generators are doing kind of that. I don't think there's any companies in my area anymore, by the way, to do gas chlorine. But this is what the saltwater generator does. So this myth kind of got propagated. I'm gonna just give the manufacturers a benefit of the doubt, and say by accident, by smart marketing, and the marketing was too good, and people just started believing this, and people still till this day will say, Yeah, I have a saltwater pool, so I don't use chlorine in my pool. Really, it's it's something that if you do pool service, it is a salt saltwater pool, it is a chlorine pool. And if you're a homeowner looking to buy a saltwater system, which by the way, I really like the saltwater systems because it's some it's a way to add chlorine to the pool without having to think about it too much. But in reality, it's probably the actual best form of adding chlorine to the pool, believe it or not. And so it is a chlorine pool, no matter how you look at it, you're just not adding chlorine products to the pool. You're not adding liquid chlorine, dichlor, trichlor, cal hypothes of the pool on a regular basis. And there are non-chlorine pool systems out there like bigwenide. I don't really have any on my route, I've never dealt with it, but that's a non-chlorine kind of pool that you can maintain without chlorine. But you're gonna need some kind of sanitizer in the pool, regardless of either with the saltwater generator or by adding chlorine. So the saltwater pool is a form of sanitizing the pool. It just requires less manual addition of chlorine to the pool. Looking for other podcasts, you go to my website, swimmingpoollearning.com on the banner, click on the podcast icon. There'll be a drop the menu of close to 1800 podcasts now. And if you are interested in my coaching program, you can learn more at poolguycoaching.com. Thanks for listening to this podcast. Have your week and God bless.