Zero Chlorine: Why You Can’t Trust Breakpoint Math Alone

Zero free chlorine is not a small problem, it’s the moment a pool can start compounding into cloudiness, chloramines, and an algae bloom. We break down what’s really happening when a pool “zeroes out,” why filtration can suddenly struggle, and how to bring sanitizer back fast without guessing and hoping for the best. 

We start with the must-have testing mindset: total chlorine, free chlorine, and combined chlorine (chloramines). Once you know your combined chlorine level, breakpoint chlorination stops being a mystery and becomes a repeatable process. We also explain why under-dosing shock can actually make a chloramine problem worse, and why many pros intentionally overshoot breakpoint in the real world to account for heavy organic load, microalgae, and the “negative chlorine demand” that eats new chlorine immediately. 

From there, we get practical about recovery tactics that actually move the needle: cleaning or backwashing the filter so the system can clear cloudy water, choosing smart helpers like phosphate remover and enzymes, and being cautious with products like PoolRx when chlorine is elevated. We also cover the aftercare that saves your week: longer pump run times for better circulation and a planned midweek check so the pool doesn’t crash back to zero before the weekend. 

• common reasons chlorine hits zero on a route
• why zero chlorine often means combined chlorine
• using total chlorine and free chlorine to calculate chloramines
• breakpoint chlorination math and why under-dosing backfires
• why we err on the side of overkill
• the “negative chlorine” idea and what drives chlorine demand
• when to use phosphate remover and enzymes
• cautions with PoolRx at high chlorine
• adding borates only after balancing pH and alkalinity
• backwashing DE and sand filters for faster recovery
• cleaning cartridge filters to speed up clearing
• planning a midweek return visit to hold chlorine
• running the pump longer for better circulation

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Transcript

Coaching Program Quick Plug

Causes And First Checks

Breakpoint Math Without Guessing

Negative Chlorine And Fast Demand

Chlorine Enhancers That Actually Help

Filter Cleaning To Clear Cloudiness

Hold Chlorine All Week

Ants Analogy And Wrap Up

SPEAKER_00 1:03

Hey, welcome to the Pool Guy Podcast Show. In this episode, I'm going to give you some really helpful real tips to deal with pools that have zero chlorine. You may run into this out there when you get to a pool and the chlorine level zeroed out. And this is something that can turn really bad on you really quickly. And I'm going to give you some really practical tips on how to bring the chlorine level up rapidly and effectively. 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 Swimmypoollearning.com. Regardless of the reason why the pool zeroed out, and there could be a variety of factors that cause this, from a pool party where the pool was overused, or maybe the customer turned the pool off on accident all week long, allowing it just to sit there, and that would zero out the chlorine, of course, or you didn't put enough chlorine in the pool the week prior, or the or there's phosphates in the water, or microalgae in the water, whatever the cause of the zero chlorine. It's important that you correct this and you do it in a timely manner to make this effective. And what I mean is that a pool with zero chlorine can compound itself and become a major problem, and there's a lot of different things that can be affected by the pool zeroing out. Number one, you may have created poor filtration at this point with the zero chlorine, which means that you may have to backwash the filter, or if it's a cartridge filter, you may have to clean it out. Because with the zero chlorine, that means that of course the water is cloudy, there's a lot of organic in the water itself, there may be algae forming in the water, and this affects the filtration system. So just by adding chlorine to the pool, it's not going to really be an effective method of taking the pool from zero chlorine to the proper level of chlorine. And I'll back up a little bit, and one of the things that you have to understand about a pool that has zero chlorine is that more than likely you also have some combined chlorine, and the chlorine is not effective in the pool. The combined chlorine or chloramines in the pool, and usually when the pool zeros out, you're gonna have some combined chlorine. There's just no way not to have combined chlorine or chloramines in the pool with zero chlorine. It's just it just happens and is something that when you test the water, and you should have a test kit, by the way, that can't test for your total chlorine, your free chlorine, your combined chlorine, giving your total chlorine number. This is really an important factor because in order to reach the break point of the combined chlorine to get rid of the chloramines in the water, you have to actually know what the combined chlorine level is in the pool water. Here's some practical mathematical examples of combined chlorine. Let's say that you tested the pool water and the total chlorine came out at two parts per million, the free chlorine is at 1.5, that means that your combined chlorine is 0.5 parts per million. So if you're doing the breakpoint formula on this, you're going to need the breakpoint is 10 times the combined chlorine number. So 10 times 10 times 0.5 parts per million is 5 parts per million. So you need to bring the chlorine level up to 5 parts per million to break this. Now just remember this for a second because I want to really highlight this so you get an idea of some problems this may have. Let's say you do the same test and the combined chlorine comes out at 2.0 parts per million. That means that you'd have to raise the chlorine level to 20 parts per million to break the combined chlorine if you're getting a combined chlorine of 2.0 parts per million. And here is the problem. If you only raise the chlorine level to 5 times that amount, let's say you bring it to 10 parts per million in this case, instead of 20 parts per million, you're actually going to make the chloramine problem even worse in the pool. You're going to add to that problem and make it a worse combined chlorine problem if you don't break it. So this is where it becomes critical that you really put enough chlorine in the pool to break the combined chlorine to get rid of the chloramines in the water, because if you put too little in there, you're going to actually make the problem a lot worse for yourself. So here's what I suggest you do, and this is very practical. This is nothing scientific. This is just something that we we do out in the field. And you want to bring the free chlorine level up to a point where it's going to be you're going to break the combined chlorine without any kind of debate or issue in breaking it. So let's say that it comes in at two parts per million of combined chlorine. In the book it says to raise it to 20 parts per million. I really highly suggest you raise it to 40 parts per million. Now you're not wasting chlorine product. If you do the math and you you'll see that you're not putting an extremely amount extreme amount of chlorine in to double that from 20 parts a million to forty parts a million, but you are guaranteeing yourself that you're going to break the combined chlorine. Without a doubt, you're going to break it by doubling it. If the combined chlorine is at 0.2 parts per million, and the book says to raise it to 5 parts a million, raising it at 10 parts per million, you're going to break it. And so the object is to make sure that there is no margin of error here, and you just want to go to the side of overkill when you're breaking combined chlorine. And again, a pool that has zero chlorine in it more than likely has some combined chlorine. I rarely would find the pool that zeroed out where I test the water. The free chlorine is at zero, you know, or 0.5 or something, and the combined chlorine is showing nothing. Really, you're going to have combined chlorine when the chlorine zeros out in the pool or gets close to zero. Another thing to consider when a pool is at zero chlorine, and this is something that I took from Bob Lowry when he was on my podcast. He mentioned this a few times is that a zero chlorine level can mean that the pool has a negative chlorine level. And if you think about it for a minute, get your brain around it, it does make a lot of sense that a pool that has zero chlorine can have what he calls a negative chlorine level, which means I think what he really meant by that is that there are a lot of things in the water at this point that will cause the chlorine you're adding to the pool to not be as effective. Again, microalgae in the water, a lot of organic bacteria that's in the water, all these things will consume the chlorine very rapidly. If you had a pool party and you had 20 people in there, they have the suntan lotion, they have their body oils, they have you know urine, everything is in the pool, and this is creating what we call would call a negative chlorine level with all this stuff in there, and that means that if you are going to try to break the combined chlorine and you need to add 10 parts per million, then you add 20 parts per million, that may not even be enough because you may be dealing with other stuff in the water. So again, you want to err on the side of adding a lot more chlorine than you think you need to the pool to make sure you break it. Believe me, I've been to pools where there's a little bit of mustard algae forming, and instead of adding what I need to add to the pool, I just add what the book calls for. Okay, you're gonna shock the pool, bring it up, maybe you're gonna add, you know, some copper algicide, whatever, or some polyquat 50 to the pool, and then you're gonna call it a day. And you get back there the next week, and the pool, the algae has bloomed to where it's covering the entire pool. So aggressively attacking the pool with zero chlorine is the way to turn this around effectively. This is also a great time to add a chlorine enhancer to the pool when you're dealing with the zero chlorine. So you can add a pular X to the pool. Now be careful with the pular X if you're gonna bring the chlorine level up really high, because if someone swims in that pool within a week or so with an elevated chlorine level, it could cause the green hair with the copper reacting with the high chlorine. Boreates to 50 parts a million will have no effect like that. So you can add the borates to 50 parts a million. Just make sure that your pH and alkalinity are in line before you add the borates again. You just can't add the borates to the pool with the pH at 8.2 and the alkalinity at 140, because then it becomes more difficult to bring that down again. So, of course, bring the pH and alkalinity in line if you're gonna add the borates. And then, of course, the easiest enhancer I think to add at this point, the one I recommend when you're dealing with zero chlorine is a phosphorate remover and enzyme because you're going to have to clean the filter anyway, usually in this case, and the phosphorylate remover is gonna really help take away a food source for the microalgae that's forming, and the enzymes are gonna help break down some of the organics in the water. And the this is a great easy thing to add to the pool when you're shocking it. You don't have to worry about any side effects. So I would say if you are gonna add a chlorine enhancer during this process, go with the phosphate remover and enzyme over the borates because sometimes you have to balance that water first and over the pool or x because when you're shocking the pool, it isn't really made for shocking a pool to that level. It's made for afterwards to maintain the pool and keep the algae from forming in that pool later. I did mention earlier how the zero chlorine does affect the filtration, and the filter really doesn't work effectively with cloudy water in the pool because the filters, depending on what kind of filter you have, of course, they do get clogged up with organic debris, with you know algae very rapidly. And this, of course, is the secondary problem when the pool gets cloudy, is that it affects the pool filtration. So, of course, a D filter and a sand filter, you want to backwash it for a minute and a half or two minutes, defilter, recharge it with dietomaceous earth, they get it back to the right amount of DE in there. Sometimes for a cartridge filter, the only option at that point is to actually take the cartridge filter apart, hose it off, put it back together. This goes a long way in helping that zero chlorine pool come from cloudy back to blue again very rapidly. I know it is time consuming sometimes to take the filter apart and clean it, and sometimes a defilter backwashing won't be as effective as just cleaning the filter entirely. And this is something that you have to keep in mind that the zero chlorine in the pool has affected the filtration system in some way, especially if it's been going on for the better part of the week, and you really get there and the pool is extremely cloudy. The filtration system has definitely been impacted by the pool zeroing out. So clean the filter, backwash it, do what you need to do to get the filtration system up and running. And then, secondary, now here is something that you have to realize about a pool that has zeroed out and you're doing the break point, getting rid of the combined chlorine or bringing the chlorine level up, is that you have to make sure that that pool is going to be able to have a good chlorine level for the entire week going forward. And this is really an important thing because once you get the chlorine level up to a certain point, let's just say that you brought it up to 30 parts per million, and it's you know, the pool's cloudy, the chlorine level was at zero, and you're trying to break this, and you know, there's a lot of stuff in the pool that you don't see, like the microalgae, things like that. By the mid middle of the week, that chlorine level can go from 30 down to near zero again pretty rapidly. This happens a lot with the green pool cleanup. You'll throw a ton of chlorine in there, you get to the next day, and the chlorine level will be at zero again. It's very common because there's a bunch of stuff in the water. The water is not cloudy for no reason, it's cloudy because there's a lot of organics in there and microalgae growing in the pool or even algae on the walls of the pool. And so this is something to consider as well that the pool may need a return visit in the middle of the week for you to shock the pool again and to bring the chlorine level up. Now, if you have a pool with zero chlorine on your pool route, going back to the pool is a hassle, but this may be something that is necessary to do to prevent the pool from really turning on you and getting out of hand. And I recommend that if you're there on a Wednesday, to get back there on a Friday to make sure there's enough chlorine to get through the weekend. And you want to, of course, if you're using trichlor tablets, double up the tablets for that week so that the chlorine level is really strong, and or maybe leave some chlorine for the customer to dump into the pool, whatever your method is, but you want to make sure that for a daily amount of chlorine that does staying high in the pool and not going back down towards zero, sometime midweek. And believe me, I've experienced this before. I've been lazy, I've I've been at a pool on a Tuesday, shocked it, thought everything was okay, and I just let it go to the next week, and I get back there, and the pool looks even worse when I get there, when I should have stopped back on a Friday to make sure the pool was recovering. And another thing that you probably should do and consider doing, and this is something that is really logical to do, is run that pool a lot longer during that period of time while you were trying to recover the zero chlorine pool. So let's say that the pool is running for 10 hours a day. Well, logically, boosting that pool up to 18 hours a day or 20 hours a day is gonna make a tremendous difference because you're gonna have much more circulation. The chlorine you add to the pool is gonna circulate in the pool a lot better. I would say even running the pool 24 hours a day if you need to is something that you can do. So if you have an enommatic timer, go ahead and turn on that pool, take off the off-tripper, and just run that pool 24-7 until that pool clears up. If you have an automatic automated system, just set the timer for 23 hours and 59 minutes and let it run basically 24 hours a day for at least those three days until you get back over there and check the pool and shock it or bring the chlorine level back up if you need to. But running the pool a much longer time after it zeros out is going to be a really effective way to make sure that the chlorine level stays high and the water is circulating, and it's something that you probably should do. Now, sometimes customers will push back on that because of electricity usage, but you really want to make it clear that it's only for a short period of time and it's something that's going to really help you turn this pool around. If you don't do this, and I've done this before where I just leave it at the way it is, normal runtime, it may take longer and it may not recover properly. So again, bringing the chlorine level up to a extremely high level, double what would be the break point, in my opinion, would be logical. Cleaning the filter, backwashing if if needed, and then just running that pool for a very long time for that three or four day period and take it back there and check it. And I really think a return visit is important in a lot of cases when you're trying to get a zero chlorine pool back in shape, and you once you fail to do this, it makes it much more difficult to get things back in shape. You have algae forming, you have cloudy water, the filtration system is still impacted, and the best way to deal with a zero chlorine pool is to really attack it, shock the pool, bring it to a a really high chlorine level, clean the filter, backwash it, stop back by there midweek, run that pool a lot longer, and you really have to be proactive with a pool that has zero chlorine because it could turn into a real mess. You can't really be flipping about it, get to the pool, if you don't check it for combined chlorine, you've already lost some of the battle right there. If you just bring the chlorine level up to 10 parts per million, you think that's gonna do it. You don't clean the filter, you don't run the pool longer, you don't go back there again midweek. Chances are that pool is not gonna turn around and you're gonna have a bigger problem on your hands the following week. A good analogy for this, and you probably experience this, you wake up in the morning and you go in your kitchen and you see two ants crawling on your counter. Well, you just kind of squish them, kill them, and then later on you'll see maybe six or seven ants, and you start squishing them and killing them, and then you go to bed at night and you don't really think about it or worry about it. You get up the next morning and there's like a million ants on the counter, you know, there's a line of them crawling everywhere, and it's just one of those things where you weren't really proactive, you were just killing a few of the scouts, and you went to bed and you woke up the next morning and the whole kitchen is full of ants, the trash can, the counter everywhere is a trail of ants. Same thing can happen with a pool that has zero chlorine. If you're not proactive and you're just kind of killing one or two things here and there, and not really taking care of the whole problem, then you're gonna be in for a world of hurt later on, just like your kitchen being infested with ants. And by the way, if you do have this ant problem in your kitchen, there's actually a really cool product, it's called Tarot Ant Killer Bait Station. So T-E-R-R-O, and it's the uh ant killer bait station T300B. If you look on Amazon, there's 151,000 reviews of this thing. They're like these little packets of borate gel that the ants crawl into and they bring it back to the colony, and it actually kills the queen. Highly effective, and it's kind of like the same thing when you're shocking the pool and doing all these things. It is a highly effective method of getting rid of the zero chlorine pool, and same with the tarot ant killer, it's like the ultimate ant killer in the kitchen, and I highly recommend doing that. So being proactive and really taking it to the nuclear level in some cases is the best way to deal with those zero chlorine pools. Looking for other podcasts, you can find those by going to my website, swingingpoollearning.com. There you can find over 1900 podcast episodes, and you can, if you're interested in the coaching program, you can learn more at PoolGuyCoaching.com. Thanks for listening to this podcast. Have the rest of your week and God bless.