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November 24, 2025 19 mins

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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Transcript

Episode Transcript

Available transcripts are automatically generated. Complete accuracy is not guaranteed.
SPEAKER_00 (01:14):
You can hypothes, and Bob Larry is going to
explain to you some things to beaware of of the differences
between both of these tablet orchlorine tablet choices.
Are you a full service prolooking to take your business to
the next level?
Join the Fool Guy CoachingProgram.
Get expert advice, businesstips, exclusive content, and get
direct support from me.

(01:35):
I'm a 35-year veteran in theindustry.
Whether you're starting out orscaling up, I've got the tools
to help you succeed.
Learn more at swimmingpoollearning.com.
From the standpoint of trichlor,why is it not the preferred
method to sanitize the pool?
I know that you know it'sagainst 90% of the pool guys are
tablet, you know, sodium bromineshocking the pool every week.

(02:00):
Why is trichlor so bad for thepool chemistry and balancing the
pool?

SPEAKER_01 (02:06):
Trichlore can be used successfully in a pool, but
the problems that it createswhen it becomes the sole source
of sanitizer are monumental.
And I say monumental becausewhen cyanuric acid level builds

(02:27):
up, it slows down the chlorine.
We finally get so muchsanitized, so much cyanuric acid
in the pool that it slows thechlorine down to where you
actually need a lot morechlorine to keep the water safe.
And this is really important tounderstand.

(02:47):
For many years, uh cyanuric acidwas thought of as just something
that protected chlorine frombeing destroyed by sunlight.
Everybody said, well, it's nobig thing if it builds up
because it's just protecting thechlorine from sunlight, so it's
not a big deal.
And eventually we came to therealization that too much

(03:11):
cyanuric acid in the pool wasaffecting the chlorine's ability
to kill things.
And it would take chlorine wouldstill kill things, but it took a
lot longer.
And then in the case of itreally building up, you could
get algae growing and all kindsof stuff growing in your pool,
even though you've got a goodchlorine reading.

(03:32):
It happens that way because it'seasy to use a tablet of chlorine
and just have it dispensechlorine all week long while
you're gone.
And you put it in a floater, youput it in a in a in an inline uh
chlorinator, and and no bigdeal.
But the big deal is that thatfor each 10 parts per million of

(03:53):
chlorine you add to the pool byusing trichlor, you also add six
parts per million of cyanuricacid to the pool.
Most pools use about one partper million of chlorine per day.
And then when you add somebeters to it, it means that that

(04:13):
the average pool uses about 10parts per million of fluorine
per week, which then means thatyou're gonna have a buildup of
six parts per million per weekof cyanuric acid or 25 parts per
million a month.
So now you've got a buildup of25 parts per million a month.
The research that me and someother people have done over the

(04:34):
years have determined that thebest way to know how much
chlorine to have in your pool isto use a percentage of cyanic
acid.
And even the MAHC and the uh AHCpeople have come up with a a
formula saying that the thechlorine to cyanic acid ratio

(05:00):
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 cardhere.
We're saying that that yourchlorine level should be 5% of
your cyanuric acid level.
And so if you have a cyanuricacid level of, say, 50 parts per

(05:22):
million, then you need 5% of 50parts per million, which is 2.5
parts per million, no problem.
But what happens now when youget up to 100 parts per million
of cyanuric acid?
Now you need 5 parts per millionof chlorine.
And if you're only keeping twoin your pool, now you're gonna
start growing algae becausethere's not enough to keep algae

(05:46):
from growing.
And so that 25 parts per millionper week starts building up.
And so in two months, now you'vegot 50 parts per million more
chlorine, more cyanuric acid inyour pool, and you need 2.5
parts per million more chlorinethan you were using.

(06:07):
And if you were using two ortwo, two to four parts per
million, now you're gonna needfour to six parts per million of
chlorine.
So you you have to compensatewhen the chlorine, when the
cyanuric acid level goes up, youhave to to add a correspondingly
higher level of chlorine.

(06:29):
And it just keeps building upbecause now you need more
chlorine and it it makes morecyanuric acid.
And now you need more chlorine,and now you are adding more
cyanuric acid, and it just keepsbuilding up and it becomes a
real problem.
And then even balancing thewater becomes a problem because

(06:49):
cyanuric acid affects the totalalkalinity reading.
And so we have to subtractone-third of the cyanuric acid

(07:18):
reading from the totalalkalinity reading to get to
carbonate alkalinity.
So we we create problems byhaving a lot of cyanuric acid.
In addition, trichlor uh isacidic.
It has a pH of between 2.8 and3.
So when you add, as it's addedto the pool, it is acidic, and

(07:40):
it's going to lower the pH andlower the alkalinity and raise
cyanuric acid.
So now you've got an additionalproblem to come up with.
You have to raise the pH outback up, and you have to raise
the alkalinity back up, and youhave to keep the cyanuric acid
from going so high.
So you've got all of theseproblems to deal with, and if

(08:01):
you weren't using cyanuric acid,you wouldn't have any of those
problems.

SPEAKER_00 (08:06):
Yeah, it's uh definitely a can of worms when
you start out.
It starts out good, and if youcan keep it balanced, it's fine,
but it sounds like it's hard todo that in best case scenarios.
And so a lot of people look atcal hypo tablets as a good
alternative.
And I just recorded a podcastwith the pool life um tablets of
the slow dissolving ones.
Um, but there's going to be somedanger, I think, and some

(08:28):
situations that are gonna comeabout now when people can't find
the trichlor tablets at theirhardware store and they see a
bucket of cal hypo tablets.
What could be a danger ofswitching from trichlor to cal
hypo?

SPEAKER_01 (08:40):
It it is a serious danger.
And if you you've only beenpaying a little bit of
attention, if you've only beenpaying a little bit of
attention, uh pay attention tothis.
If you add calhypo and trichlortogether, they will explode.
They will explode, and then theywill cause a fire.

(09:05):
Fortunately, there's usually alot of water around, so the fire
doesn't last very long, but theexplosion does.
Uh, I have seen pictures, I havetalked to many, many people when
I worked at Leslie's as theirtechnical director.
I had people calling me all thetime saying, Listen, I put some
chlorine tabs in my littlerubber ducky that's in the pool.

(09:28):
And if I I put it in there, andfive minutes later, it blew up
and launched the duck.
You know, the damn thing went upthe air five 50 feet, you know,
and came back.
And it's a good thing I wasn'tnear it, or you know, I would
have been in trouble.
I'm gonna sue you guys.
And and I would talk to him andsay, listen, on the container,

(09:50):
on the on the the rubber ducky,it says you have to use
trichlor.
And if what you bought, it saysit's cal hypo.
And both of those labels say donot mix with another chlorine
product.
And you have mixed those twotogether and caused an
explosion.
And and I'm talking serious, youguys.

(10:12):
If you put cal hypo in atrichlor feeder, even if there's
only a one or two tabs in thebottom, and you put some calipo
into it and cap it back up, waitfive minutes and it will blow up
and either blow the cap off thechlorinator, or it will it will
blow so hard, it will blow openor blast open the tube, the

(10:37):
cartridge that it's in, so thatit can get out of there.
It's just like putting afirecracker 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 itrips open the can to get out.
And it can cause a seriousproblem and it can cause a fire.

(10:59):
So you need to be very, verycareful.
The good news is that it takesusually about five minutes for
the reaction to happen.
But when you put those twothings together with a little
bit of water, which is exactlywhat's inside a chlorinator, you
know, two dry compounds and alittle bit of water, it it

(11:22):
generates heat, but it alsogenerates chlorine gas and
hydrochloric gas, those twogases.
And those two gases will be setoff at about 80 degrees
temperature, it will explode at80 degrees.
So it is really, reallyimportant that you never ever

(11:44):
mix those two things together.
And Calhypo in particular, youshould not mix anything with it.
It is more dangerous thantrichlor, and more dangerous
than dichlor and liquid and soon.
In depending on which kind ofcalhypo you buy, the 65% calhypo

(12:05):
is a class III oxidizer.
And and cal hypo has one uniqueproperty if it is if it does
catch on fire, and that is thatit supplies its own oxygen when
it burns.
So you can't smother it, youcan't use an ABC fire
extinguisher on it, you can'tuse a CO2 extinguisher on it.

(12:29):
You have to put lots and lots ofwater 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 afriend of mine.
He had lung damage for aboutthree weeks.
He opened up a trichlor tabletbucket 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 hadlung problems for about three

(12:52):
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 weexperience this at Leslie's all
the time, was people would buy a50-pound bucket of tabs and take
it home.
And by law, it is required tohave a child-resistant lid on

(13:16):
it.
I never thought that was such abig problem because you know, a
child can't reach, can'tactually reach across and open a
12-inch diameter lid anyway.
But anyway, they come with someclips and some other things on
them that you have to kind ofbreak or undo to get the lid
off.

(13:36):
And what most people do is it'ssuch a pain in the ass to get
the lid off the first time, isthey don't ever actually tighten
it all the way back down becausethey don't want to have to go
through that process of undoingthe lid the next time.
But what that does is it itallows moisture, and especially

(13:57):
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 wherethe humidity is high, then
there's a serious problembecause humidity gets into the
bucket.
Then that moisture is absorbedby the tablet, and it's enough

(14:18):
moisture to start a chemicalreaction.
And a chemical reactionliberates chlorine gas and
nitrogen trichloride.
And those two gases build upinside the the bucket, and then
you open the bucket, you getblasted in the face.
You really need to make surewhen you're putting the the

(14:42):
problem is you didn't put thelid back on all the way.
And you need to open it up, usewhat you need, and put the lid
back on.
And most guys just take the lidoff, leave it off for a couple
hours, and that's enough tostart all that chemical reaction
going.
And once the reaction starts, itdoesn't stop.
Um, you need to keep thosethings dry.

(15:04):
Um, you need to open it up anduse what you need, close it back
up and tighten it, even thoughyou 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 withthat, with gassing off, and
those vapors are gonna causeyour problem.
But and if you've got thosethings happening, just make sure

(15:24):
that your face is not near itwhen you open it, that you're
not downwind, and try to open itso that you can get it.
We used to have customersactually take buckets of
chlorine and leave them at thefront door of Leslie's when they
were closed and just leave them.
And and we had no idea who itwas from, no note on it or

(15:45):
anything.
And, you know, I mean, we'reafraid to open it up, didn't
know what to do.
And then you open it up in thestore, what is the store going
to do with it?
And so that becomes a problemtoo.
But one of the things we did waswe started finding out the big
users of chlorine.
You know, big uh health clubpools, school pools,

(16:05):
universities, colleges, thosekinds of things use lots of
chlorine.
So what we would do is we callthem up and say, listen, we'll
give you some free chlorine.
But you have to understand it'sgassing off, so you need to use
it right away.
But so we started looking foravenues to get rid of that
stuff.
Um, it can be very dangerous.
Those vapors are definitely aproblem.

SPEAKER_00 (16:27):
Yeah, and then just for the pool guys out there that
may not maybe new, when you openup a trichlor feeder, the same
thing could happen, especiallyif the elbow on the bottom is
clogged up with the paste.
When you open that up, you canalso get that same gas because
there's no the tablets aren'tdissolved and there's really no
water in there that's beenflowing.

(16:47):
And so I've had that happen tomyself where I open the lid and
that gas comes out of there whenyou'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 goodcaution 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 trichloris the fact I mentioned this to
you in the phone call, is thatthe price is at$150 a bucket
right now, roughly, uh retail.
I think when the shortage ends,I doubt if the price will go

(17:16):
down um dramatically, not gonnago 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 adifferent thing.
And I think once people switchover to another system, they're
going to find out that thecyanic acid and the triflora
created such a problem in theirpools that they're not gonna go

(17:43):
back to triflora.
Or if they do, they're onlygonna go back to using it just
minimally so that things don'tbuild up and so that it doesn't
mess up the water chemistry inthe pool.
So, you know, the goal as aservice tech is to is to provide

(18:04):
uh or to make a stable situationin the pool.
This is the goal.
And if you make it stable, thatmeans that when you come back to
the pool next week, hardlyanything has changed.
Or if there's changes, they'reonly minor.
And that's the goal because yougo back, you make a little
couple of little additions ofchemicals, you clean up the

(18:26):
pool, and you move on to thenext one.
And so you're not having to dealwith high pH, low pH, high
cyanic acid, all those thingsare all staying stable.
And that's the goal.
And that's one of the things weteach in our classes and and in
the books that I've created.
Uh, it teaches a method of doingthat.

(18:47):
And we want to make it stable sothat it's easy to take care of.
We've had companies that startfollowing this plan, and their
text can actually take on onemore pool a day because they're
saving so much time by nothaving 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 forlearning.com, where I have over
eighteen hundred podcastepisodes for you to download.
And you can, of course, downloadand listen to them at your
leisure.
And if you're interested in thecoaching program that I offer,
you can learn more atpoolguycoaching.com.
Thanks for listening to thispodcast.
Have the rest of your week.
God bless.
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