Pool Safety Alert: Chemical Hazards You Must Know

A clean pool should never cost a pair of lungs or a blown-up skimmer. We take you straight into the chemistry that turns everyday products into hazards—how waterlogged trichlor creates choking fumes, why a puck in the skimmer sends an acid slug through your heater, and the exact mixes that can explode with shocking force. With clear examples from the field and a sobering real-world fatality, we unpack what causes these reactions and show you how small changes in habit prevent big emergencies.

We break down the most dangerous pairings—trichlor with cal hypo, trichlor with liquid chlorine—and explain safer dosing strategies that rely on circulation and dilution in the full pool, not the skimmer or a five-gallon bucket. You’ll learn why calcium chloride must stand alone or it will cloud and crust your surfaces, plus how clarifiers and metal sequestering agents clash to make water milkier, not clearer. We also cover phosphate removers, overdosing pitfalls that flatten chlorine levels, and the foaming mess that follows heavy-handed enzyme or certain algaecide use—along with fast fixes and better habits.

Safety extends beyond the waterline. We outline storage and transport rules that keep acid and liquid chlorine apart in your truck and shed, reduce spill risk, and meet local compliance requirements. From opening unknown trichlor buckets without taking a lungful, to spacing chemical additions and ventilating work zones, these are practical steps any homeowner or pool pro can follow to avoid injuries, fines, and costly repairs.

• trichlor fume risks in wet buckets, feeders, and floaters
• why tablets in the skimmer damage heaters and stain surfaces
• explosive reactions between trichlor and cal hypo or liquid chlorine
• safe handling of calcium chloride as a standalone addition
• clarifier and metal sequestering agent conflicts that cause cloudiness
• phosphate remover timing and avoiding overdosing
• enzyme and some algaecide foaming and how to fix it
• storage and transport protocols to separate acid and chlorine
• city compliance, p

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Transcript

Why Chemical Mixing Kills

SPEAKER_00 1:02

Hey, welcome to the Pool Guy Podcast Show. In this episode, I'm going to talk to incompatible chemicals, how this could cause a problem with the pool by mixing certain chemicals together. And of course, there is a danger of a fatality whenever chemicals are mixed together. And I'll go over all of this for you in this podcast. You can say safe out there. 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. In February of 2025, there was a homeowner that was found deceased in his shed in Springfield, and this was attributed to liquid chlorine and acid being mixed together in the shed, causing an overwhelming toxic reaction that of course took his life at that point. And if you've ever opened up a trichlor bucket that has water in it, you know that this chemical can be or this reaction can be very overpowering. It's very much like the mustard gas that they used in World War I in the trench warfare when they were gassing each other. And it can cause pretty severe damage to your lungs as well. One of the members of my group had to see a doctor for a few months after this kind of exposure because he did have lung damage. When he took a deep breath, he had trouble. And this because of the chemical reaction between the acid and the chlorine mixing together, causing the mustard gas kind of scenario with these chemicals mixing together. So I'll spend a little bit talking about trichlor and some dangers with trichlor. And of course, as mentioned, you could have a reaction with the trichlor tablets when you have standing water. This also happens in the inline feeder, so just be careful if you've ever never been to the pool before and they have an inline trichlor feeder. When you open that up, you should, of course, open it up and be far away from there because you don't know if the tablet has been dissolving in there. There's a little ball ball-bearing type check valve in there that does get clogged up with the tablet residue, and this could cause the water not to evacuate, it causes a tablet not to dissolve in there properly, causing the same kind of reaction that you would get if you open a trichlor bucket that has water in it. Whenever I get to a new account and there's an existing trichlor bucket there, I take extreme precautions when I open it because I don't know the state of that bucket, if the lid was left off at some point during the rainstorm, if the lid wasn't secured, if the lid has a crack in it somewhere, letting moisture in there. And so whenever I get to an account again with a new trichlor bucket that I'm not familiar with, and even one that I put there, I make sure that I open the bucket and I don't have my head directly over it because that's when you can have that strong reaction and overpowering where it actually knocks you out, takes your breath away. You're gonna be gagging and coughing for a good two or three minutes to try to catch your breath again. Believe me, I've had this happen to me on maybe a couple of occasions where I had a lot of trouble catching my breath after exposure to the trichlorid tablets that were moist or had water in the bucket. You also want to avoid putting the trichlorid tablet directly in the skimmer basket. This causes a couple of problems. The first problem you're gonna experience is that if the pool somehow wasn't running for a couple days, let's say the customer left in the spa mode, or there was a problem with the pump priming and it just wasn't running, and you open up the skimmer lid with that trichlor tablet sitting in that water that's not moving, you're gonna have a similar chemical odor that's overpowering that comes out. Maybe not quite as bad as the inline chlorinator or a bucket of tablets with it with water in it, but it's still gonna be a chemical reaction that can take your breath away, so that's definitely a no-no there. And the other thing that can happen with a trichlor tablet in the skimmer basket is that when the pool turns off, a high concentration of acid water builds up. Because the trichlor tablet has a pH of around two, maybe two and a half, and that's a really low pH by the way, because you know anything below seven starts to get corrosive. And so this little body of water, pocket of water that's in the skimmer basket, maybe for 10 hours while the pool is off. When the pool turns on, that acid water shoots back into the pool, and this could cause some corrosion of the equipment, especially the heat exchange, check valves can also corrode, and you may even see chemical streaks coming out of the return line. You may see a chemical reaction or burn at the main drain of the pool or the side drains of the pool from this concentrated acid water sitting there and leaking back into the return of the plumbing. So it's not a good idea to put the trichlor tablet in the skimmer. And it's also a very bad idea to have a trichlor tablet in the skimmer and pouring anything in the skimmer like cal hypo, especially. If you pour a pound of cal hypo into the skimmer with a trichlor tablet sitting there, Ed there could be an explosion at that point with the skimmer lid, and it could be a pretty violent explosion. So cal hypo and trichlor definitely don't mix. The same reason why you can't use a cal hypo tablet in a trichlor feeder, the residue in the trichlor feeder will cause that cal hypo tablet to react with the residue of the trichlor and cause somewhat of an explosion. Some can be a large magnitude explosion where the chlorinator explodes or a small reaction, but nonetheless, you're gonna have a chemical reaction that can potentially be extremely explosive and fatal. And trichlor can react with liquid chlorine as well, so you don't want to mix those together. You wouldn't want to have a trichlor tablet and pour a gallon of liquid chlorine into the skimmer. You wouldn't want to do that anyway on a regular basis, doesn't make any sense. So let me recap. Trichlor tablets can have a toxic fume plume or fumes from the trichlor mixing with any amount of water in the trichlor bucket or the three-inch chlorinator. You may even have this in a floater if there's a lot of the trichlor residue on the side of it. You do not want to mix trichlor with calhypo nor liquid chlorine, as an explosion could take place. And you don't want to put a trichlor tablet in a skimmer because the acid in there can react and damage the pool equipment and stain the pool itself. Here are a few others that I've actually seen happen out there, and this is when you have the calcium hardness increaser, calcium chloride. You never want to add that to the pool with any kind of chemical that will react with it as far as changing the pH and alkalinity, so you don't want to use any kind of pH up or alkalinity up while you're using the calcium chloride. So, of course, avoid bicarb and sodium bicarbonate, you know, soda ash is also something that can be added to the pool, sodium carbonate that can also react to this. So, what happens when you're doing this is that it causes it to participate out of solution, and you're gonna have a cloudy pool and you're gonna have this scale on the surface that's really hard to remove. So, you definitely don't want to add again calcium chloride with any other chemical when you're adding that to raise the calcium hardness in the pool. Just pretend that this is a complete standalone chemical, and you're not gonna add anything when you add this, at least for the 24-hour period afterwards, let it dissolve in the solution, and then you can add other chemicals to it. You may want to wait longer just as a precaution, but this can happen, and I've seen it happen, and I've had group members text me with this reaction, so just be careful that you don't mix calcium chloride with any other chemical. That's going to be a standalone chemical only. Something you don't think about too much is when you're adding a stain or metal sequestering agent, you don't want to add a clarify either at the same time, because this will actually cause cloudiness in the pool and not actually remove it. The clarifier, the chemicals in the clarifier can react with the elements in the metal sequestering agents causing that cloudiness. So don't mix clarifier with any kind of metal sequestering agent in the pool. And this can happen. You may have a pool that maybe is cloudy, and then you add the clarifier, and then you notice that you also were gonna add the sequestering agent at the same time. So just be aware that it's gonna cause the pool to become very cloudy and don't mix those two together. And you don't want to mix a stain or metal remover sequestering agent with a phosphoryl remover because that will increase the cloudiness as well. So those combinations, phosphor remover, already will cause some cloudiness, but if you add it with a stain or metal sequestering agent or remover, that's gonna cause even more cloudiness to the pool. A little side note as well is that you can also overdose the pool with these stain removers, and they also lower the chlorine level in the pool, so just be careful when you're using something like Aqua Dex Biodex 50. If you see a stain that you want to try to remove with that, and the instructions call for one quart per 10,000 gallons or whatever it says based on your pool size, don't overdose that pool, don't put a gallon of this in the pool because you're gonna have the chlorine zero out, you're gonna have a hard time restoring the chlorine level in that pool because it does destroy the chlorine level in the pool as it's working, and so this is something to be aware of. And on the flip side, if you're using enzymes in the pool, this is really nothing to do with a dangerous chemical reaction. But what can happen is that if you overdose the pool with enzymes, let's say you are treating the pool and you add three times the amount of enzymes that it calls for, you can have a lot of foam in the water, it can look like a bubble bath because the reaction, the the way that the enzyme works is a suffocant, and this will of course lower the surface tension. So if you have the spa jets on, or if you have the pool return lines and it's making a lot of turbulence, this will cause the foaming. And the easy cure for this is to get some spa foam down and spray it in there, and this is something that you can easily correct. But if you get to a pool, you notice this problem. It's probably because the pool was overdosed on enzymes, and that's why it's all foamy like that. I've seen really I've seen some algricides also create this problem as well, and I assume they do the same thing that the enzymes do to create the water tension so that the bubbles can form easily on the pool surface. There are some logical storage and transportation safety protocols that you may or you should be aware of. One of them has to do with the hosta returnables. You definitely don't want to put one acid container in with three liquid chlorine containers in one case. Sometimes, if you're running short on space, it may seem logical to say, oh, let's take one acid with three chlorine, I'll put them all in the same case. But as you heard at the very beginning, when the chlorine and acid mix together, let's say the chlorine or the acid is a little bit of leakage in there, the bottom of the case has some chlorine. You put the acid in there, use it in the pool, some leakage gets in there, and then it takes only a small amount of these two chemicals mixing together because that toxic chemical smell. The gentleman that lost his life in the shed will attest to the fact that in an enclosed area like that, it can be very dangerous, and even a small exposure to it can cause lung damage. So you don't want to, of course, mix the cases up, nor do you want to turn over the empty chlorine container in the case because then the chemical is introduced into the case in some residue, and if acid gets in there somehow, you could have a reaction as well. You also want to kind of store the chlorine cases and acid cases with some separation in the bed of your truck. Because if you're in a car accident, someone hits the back of your truck, you don't want the acid and chlorine coming together and mixing together. Sometimes that's unavoidable, but it's it's best to separate the acid and chlorine as far apart. So if you have liquid chlorine, put it at the bottom of your truck and put the acid at the top. Kind of guilty of not moving them far enough apart myself, but there can be a chemical reaction with them too close together in the bed of your truck. You also never want to stack two of these cases on top of each other in the back of the truck. And I see this when pros pick up their chemicals and there's no room in the truck, they'll just take the chlorine and stack it on top of another case of chlorine. Here, the CHP will pull you over for that and give you a ticket. And this is unstable, and if it spills over and tips over, then if you have acid back there, acid residue in the bed, it's gonna react to it and cause a problem, a chemical reaction. So don't do that as well. And when you're storing it at the side of the house, of course, keep the acid and chlorine separate from each other. Don't put them in this shed next to each other where they can mix and react with each other. It's kind of common sense, but it's something that you should be aware of. There was an incident here in Hemet, California, where you know someone blew up their, I think it was the garage that had all the chemicals stored in. They had to evacuate the neighborhoods. It was a big mess. And the cities have been cracking down quite a bit on chemical storage. They'll actually look over your fence and check to see how you're storing stuff. It's not uncommon for some cities that require a permit to store chemicals now. So it's one of those things where a few people kind of ruined it for everybody. So if you have a pool service and you're licensed in a certain city or live in a city with the pool service business, the city may require you to have a chemical storage license as well, or the code enforcement may fine you or cite you for that. So, since I'm talking about some common sense things, you don't want to mix two chemicals in a bucket of water that could cause a reaction as well. You also don't want to mix anything in the skimmer. So, again, if you have a trichlor tablet in there, you don't want to pour a bag of cal hypo in there. If you're using cal hypo in the skimmer, you definitely don't want to put any trichlor tablets in there next to them. I know this doesn't sound logical, but it's common sense and these mistakes could happen. So you don't want to do that, and you just don't want to mix any chemicals together in a small body of water because there can be some kind of chemical reaction that happens. There's very little danger of adding a quart of muitic acid in a deep end of a pool, and then a few minutes later adding a gallon of liquid chlorine into that pool because you're dealing with you know 15,000 gallons of water and you're dealing with a small percentage of these chemicals in that big gigantic body of water. But in a five-gallon bucket, if you're mixing chemicals in there for whatever reason, it doesn't make a lot of sense. But if you do that, you can cause a chemical reaction, it could cause an explosion, or it could cause some toxic fumes in the lease. So you want to avoid doing that at all costs, and you just want to really treat the chemicals as something hazardous and dangerous. If you're ordering you know chemicals from your supplier from Pool Corp, the driver has to be hazmat certified to deliver a certain amount of chemicals, and so there's a limit to how many cases of liquid chlorine or muric acid they can actually bring or tablets unless they're certified, and that's for a reason because these are very dangerous chemicals, and we use them every day, and so we're kind of desensitized to the danger of these chemicals. So I just want to bring it back to your awareness that you're dealing with really toxic and hazardous chemicals out there, and really use common sense and caution, and mixing chemicals is the number one cause of reactions, damage, fatality. If you're looking for other podcasts, you can find those by going to my website, swimmingpoollearning.com, on the podcast at the banner, click on the podcast icon. There'll be a drop down menu with close to 1900 podcasts for you. And if you're interested in the coaching program that I offer, you can learn more at poolguycoaching.com. Thanks for listening to this podcast. Have a great rest of your week and God bless.