Bob Lowry Explains Why Some Products Kill Your Pool Chlorine

Zero chlorine is one of those pool problems that feels impossible because you can do everything “right” and still watch your sanitizer disappear. We dig into the real reasons it happens, especially after adding stain removers and sequestering agents meant to solve metal stains and protect surfaces. 

From there, we get clear about metal chemistry and a common misconception in pool maintenance: a sequestering agent doesn’t remove metals from pool water. It temporarily binds them, then sunlight and oxidizers break that binder down and the metal can stain again. We explore why product selection matters, how overdosing makes the problem worse, and why some treatments can raise phosphate levels that algae love. If you’re trying to protect new plaster or avoid dropping metals out of solution, this is where water care becomes a careful balancing act.

We also unpack a major source of “mystery” chlorine loss: sodium bromide based algae products. Add bromide and you can effectively turn a chlorine pool into a bromine pool, where every chlorine dose reactivates bromine instead of building a chlorine residual. That creates confusing test results, higher sanitizer targets, and fast sunlight burn-off because cyanuric acid doesn’t protect bromine the same way. We close with the non-negotiable safety message: a pool with zero sanitizer residual has no protection against waterborne infection risks, and “negative demand” can hide how much chlorine the water is actually consuming.

• stain removers and some sequestrants creating immediate chlorine demand
• overdosing metal treatment chemicals making chlorine loss worse
• phosphonate and phosphate breakdown raising algae risk
• why sequestering agents do not remove metals from water
• metal removal as an alternative to ongoing sequestration
• sodium bromide products converting chlorine pools to bromine pools
• test kit confusion when bromine reads like chlorine
• sunlight destroying bromine faster without cyanuric acid protection
• zero chlorine safety risks including infection transmission
• negative chlor

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Transcript

Stain Removers Create Chlorine Demand

SPEAKER_00 1:06

And then we're going to go over some products that you can add to your full or the when you add it to the full activity today. Zero out the chlorine level. And these are things that you should be aware of when products actually affect the chlorine and can, of course, zero out the chlorine in the pool. Are you a full 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. So let's talk about zero chlorine in the water. Recently, I and I've done this myself where you add a stain, a chemical that's going to remove a stain or a sequestering agent, and basically the chlorine zeroes out in the pool. They can't recognize the fact that you're putting in this kind of thing and so it oxidizes and all the chlorine's gone in the pool. And one thing is that you go back the next week, you put chlorine in, and the same thing happens again. So is there a way to tell a breaking point when you put in one of these stain remover chemicals and it zeroes out to chlorine? When is it going to hold chlorine again, I should say? Or how do you get it to hold chlorine again when you when you because you don't want to shock the pool when you put a sequestering in?

Sequestering Agents And Phosphate Risk

SPEAKER_02 2:22

I think it goes beyond or to a step before that, and that is your selection of a sequestering agent or a stain remover. And many of the stain removers use a chemical that is oxidizable by chlorine. And so when you put it in, and especially because some people have the idea that if if this amount is good, adding a little more is probably better. So they put in a you know one and a half or two times what the bottle says, and so they put some in, and then they try to chlorinate after that. Well, they just put something in that needs to be oxidized, and now they're putting in an oxidizer. You know, the two just are not compatible. Once the sequestering agent has filled up with metal, if you will, then there's the chlorine can go round free because the sequestering agent and the metal are kind of bonded together and holding on to one another, so chlorine doesn't have to act on them too much. But there are different versions of sequestering agents. And some are triethanolamine, some are are phosphonates, some are other kinds of orthophosphorus compounds. You know, you can create an algae problem because the orthophosphate and phosphonate products degrade into phosphates. And now you've got a pool full of phosphates, which algae love as their primary source of nutrition. So you put the stain remover in to get rid of the stain, and you end up with maybe an algae problem. And and invariably, this is what happens is you put a stain remover in, you start growing algae, but you haven't seen the algae yet. So regular amounts of chlorine get consumed trying to kill the algae. It may or may not be the oxidizer demand of the sequestering agent. It may be the fact that you've actually started uh growing some algae, and the algae is creating the chlorine demand. And algae can be growing for a while before you actually see it. You don't actually see that dense green color or black color or blue-green color until it's actually colonized a little bit and has grown for a while. So that might be the reason.

SPEAKER_00 5:10

And the person that called me kept going back week after week. He didn't really want to shock it because of the new plaster, and it was just a stain on there he was trying to get off of. Is there is there a way to you know counter, like how would you know when the pool's not going to be zero out every week? Is there like some way to calculate this particular effect when you put something in the pool? Not just the stain removers, but other products also I've seen.

Removing Metals Instead Of Hiding

SPEAKER_02 5:34

Well, the the manufacturers are supposed to put on the label, or they should put on the label that their products are incompatible with anything. I'm uh a little more of a believer when it comes to stains in removing the metal and not just sequestering it. And and I think that service techs and homeowners and a lot of people make a mistake thinking that a sequestering agent removes the metal from the water, and that doesn't happen. What it does is a sequestering agent has a unique shape as a molecule, it can surround molecules of metal so that the metal can't can combine with anything else and cause a stain or precipitate. And so it just surrounds that metal molecule and keeps it from combining with anything. Well, the sequestering agent is organic, man-made, and because it's man-made, it gets degraded by sunlight, oxidizers, chlorine, ozone, so on. It gets oxidized. And when it gets oxidized, it breaks down, and eventually it breaks down and leaves the metal again to call to be able to cause a stain. So the the metal is still in the pool, it's not gone. And when the sequestering agent breaks down, the metal is free to cause a stain. We need a way to actually get rid of the metal. And there's at present only one company that makes a device that will do that, and it's in a little bag or a little cage that you can put in your skimmer. And you put it in the skimmer, and water flows through your skimmer, and as it does, this little bag grabs on to the metals and keeps it in that bag. And the metal that was in the water is gone.

SPEAKER_00 7:45

Yeah, and that's the sea later product. I can mention them because I'm good friends with them over there, and I know that that product works well.

Sodium Bromide Turns Pools To Bromine

SPEAKER_02 7:51

I know them very well, and they're great people. And as you know, I don't mention brands.

SPEAKER_00 7:56

I know, but I can throw that out because people are gonna be wondering what that is. So it's a C later 4.0 or 1.0. And then another way chlorine zeroed out a lot is the pool pro will put a lot of sodium bromide in the pool. They're treating algae and they're using an algae product with that in there, and then they zero out the chlorine that way too. You know, what are the dangers of using that product in the pool over and over again? And you're gonna be getting zero chlorine readings a lot when you overdo it.

Zero Chlorine Safety And Negative Demand

SPEAKER_02 8:21

Well, you may or may not get a zero reading, but here's what happens if you use a bromide, sodium bromide-based alga side, and there are many of them on there, but bear in mind that any algae product has to say on the label the ingredient. So you need to read the label a little bit and see if it says sodium bromide. And if it says sodium bromide, when you put that in the pool, you have now changed the pool to a bromine pool. And it may be good for getting rid of algae because hypogromous acid is a little better at killing algae than chlorine is. So, and it's also something that the algae is not used to. You know, don't you have to remember that that you've been keeping chlorine in the pool and the algae grew with the chlorine in it. So it's kind of used to chlorine. So when it sees bromine, it's not used to it. So bromine makes it pretty effective. So it's an effective algacide, but any amount of bromide left in the water, when you add chlorine to the pool, that bromide gets activated by chlorine into the killing form of bromine called hyperbromous acid. And then when the hyperbromous acid kills something, it reverts back to bromide. And then when you add more chlorine, it reactivates the bromine. So all the chlorine that you put in the pool is reactivating the bromide, and it's not going away. And especially if you use the the I I ran the dose on a couple of the bromide-based algebra, and when you put that in, you're actually putting about three parts per million bromide into the water. And what that means is every time you add three parts per million of chlorine, the chlorine is all used in making bromine in the pool. And so you're not making chlorine anymore, and there's problems with that because you're looking at your at your test kit thinking you've got three parts per million of chlorine when you've actually got three parts per million of bromine. And bromine, we recommend a level of four to six parts per million of bromine in the pool, not two to four. So you need twice as much of it. And your test kit thinks it's measuring chlorine and it's measuring bromine. And the other thing that that happens is bromine can be degraded by sunlight, so the cyanuric acid that's in your pool isn't protecting the bromine, and as a result, you are you go through a lot of chlorine because you're creating bromine, sunlight is killing off of the bromine that's in the pool at a rate of 65% in two hours, and that means in about five hours you zero out the chlorine, and there's no way to to stop it. The cyanric acid isn't doing anything for it, so you'd be using a huge amount of chlorine in the pool and wondering why. If you used a bromine-based product and you've used very much of it, the only way to get rid of the bromide is to drain most of the water out of the pool. There's no other solution, there's no way to precipitate it. I've heard sales reps from the companies that make these algecides and they say it's not a problem. And I'm telling you, it is a problem. And you will have you will be using huge amounts of chlorine in your pool. You can have stuff growing because you've only got actually half of the reading you think you do.

SPEAKER_00 12:20

Yeah, so you know, whether the pool zeroed out through a sequestering agent or a stain remover or through using too much sodium broma, what would be the, you know, the bottom line, the danger of a pool with zero chlorine. I know it's unsafe, but go over like, you know, if you're doing this on your pool router if a customer is doing this and they zero out the chlorine and then they want to use the pool, what would be the inherent danger of something like that?

SPEAKER_02 12:43

It's the same thing I mentioned in another cast is that the the danger is that there's no residual in the water to prevent any beta-to-bader disease transmission. And and this is important because you can get ear infections, eye infections, nose infections, throat infections, lung infections, a lot of things you can get from being in the water. And if you've got no residual, you got zero protection. And understand this that it's possible to go to a negative demand, which means that you could add a you'll have to add a an amount of chlorine just to get back to zero. And then after that, you will start to make start to get a residual. But I've seen pools where we've added five pounds of shock to a pool and it disappears. And it disappeared because your test kit doesn't go negative, it only goes to zero. So you don't know how much negative it is. You may have had a negative 10 parts per million.

Key Warnings And Where To Learn More

SPEAKER_00 13:54

Yeah, so that's the problem with using these things because it they're very useful in the industry, but there are some cautions because of the side effects and zero, you know, having a pool with zero chlorine and you can't shock it because then the metals will drop out of solution again. So it's pretty tricky. It's a pretty tricky process. But I think one thing I think that we should put out there is that if you are using stain removers or sequestering agents, that that the pool could be unsafe, right?

SPEAKER_02 14:19

It's it's possible that if you use a sequestering agent that you wipe out the chlorine, and and who knows how long that means it's gonna be with zero chlorine. You know, if it's a service call and it's a one call a week, if it was a day after the guy showed up, it could be six days without chlorine. Yeah, that is a very long time to go with no chlorine.

SPEAKER_00 14:42

Yeah. So I think you know, that's something that people should be aware of when they're treating stuff like that. That there are side effects to that. So I think if you're new and you're using sequestering agents or any kind of stain remover, just be aware of the fact that these can and tend to zero out the chlorine level in a pool. And that's something that you're gonna learn maybe the hard way if you're not too familiar with using these products. Just one of the side effects that happens. And I hope you found it helpful going over some of the things to look out for when using these type of products in your pool or sodium bromide, something of that nature. And what can happen is of course the chlorine level could zero out in the pool. And if you're looking for other episodes, you can go to my website, swingforlearning.com, on the banner, click on the podcast icon. There'll be over 1900 podcasts for you to download and listen to. And 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.