Is It Time to Ditch Trichlor? Bob Lowry Weighs In

Ever wondered why your chlorine test reads fine but algae still shows up? We pull back the curtain on the hidden math behind tablets, explaining how cyanuric acid quietly slows chlorine and why a “set-and-forget” trichlor program can turn into a chemistry treadmill. You’ll learn the simple 5% rule—keep free chlorine at roughly five percent of your CYA—and see how that single ratio restores predictability and keeps water safe.

We dig into the side effects most people miss: trichlor’s low pH and its impact on alkalinity, the need to correct for CYA when calculating carbonate alkalinity, and the way weekly consumption can add around 25 ppm CYA per month. Then we tackle a critical safety topic: switching to calcium hypochlorite tablets. Mixing cal hypo with trichlor—even residue in a feeder—can create heat, toxic gases, and an explosion within minutes. We share real-world incidents, what causes them, and the exact precautions pros use to avoid disaster. You’ll also get practical storage and handling tips to prevent gassing from humid buckets and stagnant feeders, plus clear steps to open containers safely.

• why trichlor’s CYA load weakens chlorine
• the 5% chlorine-to-CYA rule for clear water
• the feedback loop that drives CYA higher
• trichlor’s acidity pushing down pH and TA
• correcting alkalinity by subtracting a third of CYA
• hazards of mixing trichlor and cal hypo
• safer handling, storage, and opening practices
• feeder gas risks and how to avoid them
• cost and availability trends for trichlor
• building a stable, low-drift maintenance plan
• resources, classes, and coaching for pros

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Chapters

• 2:02 Sponsor And Coaching Invitation
• 2:32 Why Trichlor Isn’t Preferred
• 3:54 Cyanuric Acid And The 5 Percent Rule
• 7:24 The Runaway CYA Cycle And Balance
• 8:42 Trichlor’s Acidity And Side Effects
• 9:13 Considering Cal Hypo Tablets
• 9:31 The Explosion Hazard Of Mixing Tabs
• 11:37 Storage, Gassing, And Bucket Safety
• 14:01 Price, Availability, And Switching Strategies
• 18:38 Stability As The Service Tech’s Goal
• 19:58 Resources And Closing

Transcript

SPEAKER_00: 1:14

You can hypothes, and Bob Larry is going to explain to you some things to be aware of of the differences between both of these tablet or chlorine tablet choices. Are you a full service pro looking to take your business to the next level? Join the Fool 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. From the standpoint of trichlor, why is it not the preferred method to sanitize the pool? I know that you know it's against 90% of the pool guys are tablet, you know, sodium bromine shocking the pool every week. Why is trichlor so bad for the pool chemistry and balancing the pool?

SPEAKER_01: 2:06

Trichlore can be used successfully in a pool, but the problems that it creates when it becomes the sole source of sanitizer are monumental. And I say monumental because when cyanuric acid level builds up, it slows down the chlorine. We finally get so much sanitized, so much cyanuric acid in the pool that it slows the chlorine down to where you actually need a lot more chlorine to keep the water safe. And this is really important to understand. For many years, uh cyanuric acid was thought of as just something that protected chlorine from being destroyed by sunlight. Everybody said, well, it's no big thing if it builds up because it's just protecting the chlorine from sunlight, so it's not a big deal. And eventually we came to the realization that too much cyanuric acid in the pool was affecting the chlorine's ability to kill things. And it would take chlorine would still kill things, but it took a lot longer. And then in the case of it really building up, you could get algae growing and all kinds of stuff growing in your pool, even though you've got a good chlorine reading. It happens that way because it's easy to use a tablet of chlorine and just have it dispense chlorine all week long while you're gone. And you put it in a floater, you put it in a in a in an inline uh chlorinator, and and no big deal. But the big deal is that that for each 10 parts per million of chlorine you add to the pool by using trichlor, you also add six parts per million of cyanuric acid to the pool. Most pools use about one part per million of chlorine per day. And then when you add some beters to it, it means that that the average pool uses about 10 parts per million of fluorine per week, which then means that you're gonna have a buildup of six parts per million per week of cyanuric acid or 25 parts per million a month. So now you've got a buildup of 25 parts per million a month. The research that me and some other people have done over the years have determined that the best way to know how much chlorine to have in your pool is to use a percentage of cyanic acid. And even the MAHC and the uh AHC people have come up with a a formula saying that the the chlorine to cyanic acid ratio should be 20 to 1. And we've been recommending 5% for a long time. 20 to 1 is 5%. So we're all on the same card here. We're saying that that your chlorine level should be 5% of your cyanuric acid level. And so if you have a cyanuric acid level of, say, 50 parts per million, then you need 5% of 50 parts per million, which is 2.5 parts per million, no problem. But what happens now when you get up to 100 parts per million of cyanuric acid? Now you need 5 parts per million of chlorine. And if you're only keeping two in your pool, now you're gonna start growing algae because there's not enough to keep algae from growing. And so that 25 parts per million per week starts building up. And so in two months, now you've got 50 parts per million more chlorine, more cyanuric acid in your pool, and you need 2.5 parts per million more chlorine than you were using. And if you were using two or two, two to four parts per million, now you're gonna need four to six parts per million of chlorine. So you you have to compensate when the chlorine, when the cyanuric acid level goes up, you have to to add a correspondingly higher level of chlorine. And it just keeps building up because now you need more chlorine and it it makes more cyanuric acid. And now you need more chlorine, and now you are adding more cyanuric acid, and it just keeps building up and it becomes a real problem. And then even balancing the water becomes a problem because cyanuric acid affects the total alkalinity reading. And so we have to subtract one-third of the cyanuric acid reading from the total alkalinity reading to get to carbonate alkalinity. So we we create problems by having a lot of cyanuric acid. In addition, trichlor uh is acidic. It has a pH of between 2.8 and 3. So when you add, as it's added to the pool, it is acidic, and it's going to lower the pH and lower the alkalinity and raise cyanuric acid. So now you've got an additional problem to come up with. You have to raise the pH out back up, and you have to raise the alkalinity back up, and you have to keep the cyanuric acid from going so high. So you've got all of these problems to deal with, and if you weren't using cyanuric acid, you wouldn't have any of those problems.

SPEAKER_00: 8:06

Yeah, it's uh definitely a can of worms when you start out. It starts out good, and if you can keep it balanced, it's fine, but it sounds like it's hard to do that in best case scenarios. And so a lot of people look at cal hypo tablets as a good alternative. And I just recorded a podcast with the pool life um tablets of the slow dissolving ones. Um, but there's going to be some danger, I think, and some situations that are gonna come about now when people can't find the trichlor tablets at their hardware store and they see a bucket of cal hypo tablets. What could be a danger of switching from trichlor to cal hypo?

SPEAKER_01: 8:40

It it is a serious danger. And if you you've only been paying a little bit of attention, if you've only been paying a little bit of attention, uh pay attention to this. If you add calhypo and trichlor together, they will explode. They will explode, and then they will cause a fire. Fortunately, there's usually a lot of water around, so the fire doesn't last very long, but the explosion does. Uh, I have seen pictures, I have talked to many, many people when I worked at Leslie's as their technical director. I had people calling me all the time saying, Listen, I put some chlorine tabs in my little rubber ducky that's in the pool. And if I I put it in there, and five minutes later, it blew up and launched the duck. You know, the damn thing went up the air five 50 feet, you know, and came back. And it's a good thing I wasn't near it, or you know, I would have been in trouble. I'm gonna sue you guys. And and I would talk to him and say, listen, on the container, on the on the the rubber ducky, it says you have to use trichlor. And if what you bought, it says it's cal hypo. And both of those labels say do not mix with another chlorine product. And you have mixed those two together and caused an explosion. And and I'm talking serious, you guys. If you put cal hypo in a trichlor feeder, even if there's only a one or two tabs in the bottom, and you put some calipo into it and cap it back up, wait five minutes and it will blow up and either blow the cap off the chlorinator, or it will it will blow so hard, it will blow open or blast open the tube, the cartridge that it's in, so that it can get out of there. It's just like putting a firecracker in a in a in a in a pail or in a can. You know, it blows up the can, and that's exactly what happens. There's no room for it, and it rips open the can to get out. And it can cause a serious problem and it can cause a fire. So you need to be very, very careful. The good news is that it takes usually about five minutes for the reaction to happen. But when you put those two things together with a little bit of water, which is exactly what's inside a chlorinator, you know, two dry compounds and a little bit of water, it it generates heat, but it also generates chlorine gas and hydrochloric gas, those two gases. And those two gases will be set off at about 80 degrees temperature, it will explode at 80 degrees. So it is really, really important that you never ever mix those two things together. And Calhypo in particular, you should not mix anything with it. It is more dangerous than trichlor, and more dangerous than dichlor and liquid and so on. In depending on which kind of calhypo you buy, the 65% calhypo is a class III oxidizer. And and cal hypo has one unique property if it is if it does catch on fire, and that is that it supplies its own oxygen when it burns. So you can't smother it, you can't use an ABC fire extinguisher on it, you can't use a CO2 extinguisher on it. You have to put lots and lots of water on it to put it out.

SPEAKER_00: 12:32

And you can also get seriously injured when opening up a trichlor bucket. We should also mention this too. And this has happened to a friend of mine. He had lung damage for about three weeks. He opened up a trichlor tablet bucket that was full of water, and when he opened that lid up, that gas almost knocked him out. And he was a doctor, and he had lung problems for about three weeks or a month. So it's very dangerous, too.

SPEAKER_01: 12:56

It is very dangerous, and and what happens with trichlor tabs, and we experience this at Leslie's all the time, was people would buy a 50-pound bucket of tabs and take it home. And by law, it is required to have a child-resistant lid on it. I never thought that was such a big problem because you know, a child can't reach, can't actually reach across and open a 12-inch diameter lid anyway. But anyway, they come with some clips and some other things on them that you have to kind of break or undo to get the lid off. And what most people do is it's such a pain in the ass to get the lid off the first time, is they don't ever actually tighten it all the way back down because they don't want to have to go through that process of undoing the lid the next time. But what that does is it it allows moisture, and especially in, depending on where you are, if you're in, say, you know, Las Vegas or something like that, the humidity is not a problem. But if you're in a place where the humidity is high, then there's a serious problem because humidity gets into the bucket. Then that moisture is absorbed by the tablet, and it's enough moisture to start a chemical reaction. And a chemical reaction liberates chlorine gas and nitrogen trichloride. And those two gases build up inside the the bucket, and then you open the bucket, you get blasted in the face. You really need to make sure when you're putting the the problem is you didn't put the lid back on all the way. And you need to open it up, use what you need, and put the lid back on. And most guys just take the lid off, leave it off for a couple hours, and that's enough to start all that chemical reaction going. And once the reaction starts, it doesn't stop. Um, you need to keep those things dry. Um, you need to open it up and use what you need, close it back up and tighten it, even though you even though it's a pain in the neck to get it back off, because if you don't, you're gonna create a real problem with that, with gassing off, and those vapors are gonna cause your problem. But and if you've got those things happening, just make sure that your face is not near it when you open it, that you're not downwind, and try to open it so that you can get it. We used to have customers actually take buckets of chlorine and leave them at the front door of Leslie's when they were closed and just leave them. And and we had no idea who it was from, no note on it or anything. And, you know, I mean, we're afraid to open it up, didn't know what to do. And then you open it up in the store, what is the store going to do with it? And so that becomes a problem too. But one of the things we did was we started finding out the big users of chlorine. You know, big uh health club pools, school pools, universities, colleges, those kinds of things use lots of chlorine. So what we would do is we call them up and say, listen, we'll give you some free chlorine. But you have to understand it's gassing off, so you need to use it right away. But so we started looking for avenues to get rid of that stuff. Um, it can be very dangerous. Those vapors are definitely a problem.

SPEAKER_00: 16:27

Yeah, and then just for the pool guys out there that may not maybe new, when you open up a trichlor feeder, the same thing could happen, especially if the elbow on the bottom is clogged up with the paste. When you open that up, you can also get that same gas because there's no the tablets aren't dissolved and there's really no water in there that's been flowing. And so I've had that happen to myself where I open the lid and that gas comes out of there when you're not expecting it.

SPEAKER_01: 16:53

Exactly.

SPEAKER_00: 16:55

So, yeah, so that's that's a lot of dangers with the trichlor that I think is a good caution for the listeners here. But let's talk also about um, and I guess we'll just touch real quick. I think the future of trichlor is the fact I mentioned this to you in the phone call, is that the price is at$150 a bucket right now, roughly, uh retail. I think when the shortage ends, I doubt if the price will go down um dramatically, not gonna go back down to$80 wholesale again.

SPEAKER_01: 17:21

No, it's not ever gonna go down, go back down, and availability is gonna be a different thing. And I think once people switch over to another system, they're going to find out that the cyanic acid and the triflora created such a problem in their pools that they're not gonna go back to triflora. Or if they do, they're only gonna go back to using it just minimally so that things don't build up and so that it doesn't mess up the water chemistry in the pool. So, you know, the goal as a service tech is to is to provide uh or to make a stable situation in the pool. This is the goal. And if you make it stable, that means that when you come back to the pool next week, hardly anything has changed. Or if there's changes, they're only minor. And that's the goal because you go back, you make a little couple of little additions of chemicals, you clean up the pool, and you move on to the next one. And so you're not having to deal with high pH, low pH, high cyanic acid, all those things are all staying stable. And that's the goal. And that's one of the things we teach in our classes and and in the books that I've created. Uh, it teaches a method of doing that. And we want to make it stable so that it's easy to take care of. We've had companies that start following this plan, and their text can actually take on one more pool a day because they're saving so much time by not having a pool that's a pain in the neck.

SPEAKER_00: 19:04

If you're looking for other podcast episodes, you go to my website, swimming for learning.com, where I have over eighteen hundred podcast episodes for you to download. And you can, of course, download and listen to them at your leisure. 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 the rest of your week. God bless.