Balance or Bust: Finding the Ideal pH with Eric Knight

Forget the old rule that outdoor pools must live at 7.4 pH. We dig into why cyanuric acid, not pH, is the dominant force behind chlorine strength in the sun, and how reframing your strategy around the FC-to-CYA ratio can reduce algae, cut costs, and protect your surfaces. With insights from industry committee work and modeling, we explain why a 20:1 CYA-to-free chlorine ceiling matters, why 30–50 ppm CYA often hits the sweet spot, and how to choose targets that keep chlorine working without drifting into overstabilized territory.

We also tackle a costly habit: aggressive acid dosing. Most techs are using far more acid than needed to move from 8.0 to 7.5, and that overcorrection hammers the Langelier Saturation Index, etches plaster, and invites oxidation. We walk through accurate acid calculations, the importance of pre-dilution, and circulation techniques that avoid “acid plunges” to the floor. Along the way, we separate the roles of pH and alkalinity, show how alkalinity drives acid demand, and spotlight calcium hardness as the quiet anchor that stabilizes LSI so your system doesn’t whiplash week to week.

Finally, we compare outdoor and indoor realities. Without CYA, indoor pools follow the classic rule where pH directly sets chlorine strength. Outdoors, stabilizer changes the game—so stop chasing numbers that don’t deliver. The payoff is fewer algae battles, stronger sanitation, and longer-lasting surfaces through a measured, data-first approach. If this perspective helps, subscribe, share the show with a colleague, and leave a quick review so more pros can rethink their chemistry playbook.

• Why eye pH claims mislead
• How CYA binds chlorine and alters strength
• The 20:1 CYA-to-free chlorine ceiling
• Targeting 30–50 ppm CYA for balance
• Acid overuse, LSI crashes, and surface damage
• Pre-diluting acid and correct dosing amounts
• Alkalinity as buffer and its components
• Calcium hardness as the quiet LSI anchor
• Indoor pools without CYA follow classic pH rules
• Why pH “bounce” often comes from bad aci

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Episode Transcript

SPEAKER_00 (01:50):
Hey, welcome to the Fool Guy Podcast Show.
This is the longest runningindustry podcast show.
As after my test season, I'vebeen doing this for nine years,
and I thank the loyal listenerswho have tuned in over those
years.
And today I'm going to continuemy interview from 2020 with Eric
Knight.
He was formerly from Arenda andHasa.

(02:13):
He's now the executive directorof Waterscape University.
And in this episode, we're goingto talk about the ideal Ph
level.
You'll find these episodesreally relevant today.
And again, I want to thank theloyal listeners who have tuned
in throughout the seasons.
Are you a full service prolooking to take your business to
the next level?
Join the Pool Guy CoachingProgram.
Get expert advice, businesstips, exclusive content, and get

(02:35):
direct support from me.
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 atswimmingpoollearning.com.
And so the homeowners that aretrying to keep their pH at 7.4
is pretty much something thatyou don't recommend with this
new center.
Yeah.

SPEAKER_02 (02:55):
Yeah, it's it's kind of self-defeating because we've
been taught, right?
And another thing is I was acompetitive swimmer.
I hear it all the time that thisconventional wisdom in the
industry is, oh, well, you haveto have a 7.4 to 7.6 because
that's the pH of your eyes.
That's not true.
Uh a simple Google search willtell you that's not true.

(03:16):
Now it is supposed to be the pHof your blood, uh, 7.4, but your
eyes, depending on how hydratedsomebody is, and I looked at
sources like the World HealthOrganization, like not just uh
Wikipedia here.
Depending on the hydration levelof the person, your eyes pH can
range from the mid-sixes to themid-eights, and that's a huge

(03:38):
fluctuation in pH.
And as a swimmer, I could nevertell the pH of a pool.
I could tell if there weredisinfectant byproducts in
there, I could tell if therewere a lot of chloramines
because that would beirritating.
I could never tell a pH swing.
So that that's a myth.

SPEAKER_00 (03:54):
Um, so the biggest takeaway for the listener with
this discussion here, with therelationship between the pH and
chlorine.
We know the old thinking is thatthe lower the pH, the more
effective the chlorine.
But now we've talked aboutthrowing CY into the equation.
So let's say that someone'scyaneric acid level is 100 in
their pool.
What would be something thetakeaway from having the high

(04:16):
cyaneric acid in the pool likewe mentioned would make the
chlorine less effective?
Um and so the best way, in youropinion, to manage the pool is
to have a lower cyaneric acidlevel and not to be overly
concerned about keeping the pHwithin that small range that
we've been taught, right?

SPEAKER_02 (04:34):
Yes, that's a that's a good way to summarize it.
So for instance, 100 parts permillion stabilizer, like you
just said, if you're trying tokeep algae from growing in your
pool and you're not doingproactive measures like removing
phosphates, you have to have aminimum of 7.5% of your CYA to
stave off algae and to preventit.

(04:56):
So that's 7.5 parts per millionof free chlorine that you must
maintain in order to stay aheadof algae.
And that's that's the closestestimate that has been
extrapolated from models.
And we got that number from aguy named Richard Falk, who's on
these committees.
Uh, he's on the ad hoc committeefor CYA.
In fact, most of our informationcomes directly from him.

(05:18):
Um, he's the guy who publishedthat chart that I just showed
earlier.
So the CYA ratio, or the CYA tofree chlorine ratio, according
to that committee, should notever exceed 20 to 1.
20 parts per million CYA forevery one part per million free
chlorine.
If you go over that, you'reconsidered overstabilized.

(05:41):
My opinion, you don't ever wantto go anywhere near that.
So for a homeowner listening ora pool service guy, just make
sure you're not overstabilizedand you're below that ratio
because you will get thesunlight protection you need at
30 to 50.
Uh, but your chlorine will getused up a little bit faster.
That's not necessarily fromsunlight.

(06:02):
That's because it's workingfaster to do its job.
So uh, you know, it's a it's abit of a trade-off, but that is
a much more reliable strategy, Iwould say.

SPEAKER_00 (06:11):
And so overfocusing on pH is probably not the way to
do it if you wanted to balancethe pool correctly.

SPEAKER_02 (06:17):
Correct, because that fluctuation in pH is going
to throw off your LSI too.
If you're making big dips downto 7.2 and you know it's going
to be coming back up to 8.0 bythe end of the week, that's a
dramatic difference.
That's a huge swing on the LSI.
I would much prefer that lowerthe pH to like 7.6 or maybe a

(06:40):
stabilizer in their pool.
And I'll be the first to tellyou, I know that sounds really
counterintuitive and it's itsounds very contrarian.
Look at the data.
We didn't publish the data.
All I'm doing is I'm just themessenger.
It won't impact your chlorinestrength, provided you're not
overstabilized with CYA.
Let's not forget, there are alot of pools that don't use any

(07:02):
stabilizer, like indoor pools.
On an indoor pool, pH absolutelycontrols the strength of the
chlorine.
So it's not like that lesson isfalse, it's that it gets
overpowered because you have astronger, uh, you know,
basically a stronger variable inthere called cyanuric acid.
So it and it is, it's it's ait's kind of like a punch in the

(07:25):
gut.
It's how it was described to meby veteran pool guys who have
been doing this their wholetime.
Let me ask you a question.
Uh, on your pool route, you'vebeen doing this for a long time
and you really know your stuff.
20,000 gallon pool.
You've treated a bunch of those,right?

SPEAKER_00 (07:38):
Mm-hmm.
Correct.

SPEAKER_02 (07:40):
The pH is eight when you get there, which is very
common because pH is going toclimb.
You want to lower it to 7.5.
How much acid does that take?

SPEAKER_00 (07:48):
Yeah, so it takes probably um a good half gallon,
I would say, or close to that.

SPEAKER_02 (07:54):
You know, vast majority of people, I would say
nine out of ten at least aroundthe country give the same exact
answer half gallon to a gallon.
In reality, it's more like acourt.

(08:24):
And most people don't know that.
And that's not an indictment onyou.
But what's happened is peopleforget other factors.
And so, in in reality, we got tomeasure the acid because if you
are putting in a half gallon,that's way more acid than you
need.
And if you follow the arena app,half gallon of acid from an 80
pH in a 20,000 gallon poolactually drops your pH to more

(08:48):
like 6.7 to 6.8, not 7.5.
Well, what do you think that didto the LSI?
This is how liners fade.
This is how liners andfiberglass uh shells
deteriorate.
And for fiberglass, once thatgel coat starts deteriorating,
chlorine starts oxidizing itbecause it's opened up, which

(09:08):
we're learning a lot more aboutthat too.
But especially for plasterpools, it you know, acid plunges
to the bottom of the pool andyou get an overcorrection
locally, and it causes a realmess.
And I like to say this is thetruth, we don't get called to
the good pools.
I've only been doing this threeand a half years, nobody's ever

(09:29):
invited me to a good pool.
It's always a problem pool.
And I will tell you, the vastmajority of the problems that I
see have to do with acid beingpoured incorrectly or too much
for a sustained amount of time,whatever it is.
And it's because of thispsychology that we have to keep
lowering the pH every week.
And and you kind of do, but notdown to 7.4 or below.

(09:53):
That means that habit needs tochange, and we have to add acid
correctly by pre-diluting it.

SPEAKER_00 (10:01):
Now, I guess I can throw another variable in there
since um we're talking about thepH and the effect on the water.
Um, alkalinity.
So it's a buffer to pH in thewater.
And I know that with cyanericacid, you have to do the
adjusted alkalinity.
I've done uh a podcast on thatone before also.
Um so if the high alkalinity isreally high in the pool, which

(10:23):
in California we do have somepools with very high alkalinity
out here, and if the alkalinityis really high in the pool, the
cyaneric acid level, let's sayit's in range in the pool, but
the alkalinity is really high.
When you add that muratic acidto the pool, doesn't the
alkalinity buffer that in someways?

SPEAKER_02 (10:41):
It it will.
Let me make sure I understandyour question though.

SPEAKER_00 (10:45):
Okay.

SPEAKER_02 (10:45):
You're saying uh are you asking when you add acid to
a pool, is alkalinity going toslow down the pH drop?
Is that what it's yeah, it'slike a buffer.

SPEAKER_00 (10:56):
Well, um, you know, it takes the old rule of the old
thinking, or maybe it's astandard thinking still, even
without the adjusted alkalinity,is that if the alkalinity is at
200, it's gonna take more, it'sgonna even if you put in a half
a gallon of acid in that same20,000 gallon pool, um, the pH
is gonna bounce much quickerback up because of the

(11:17):
alkalinity as a buffer in there,versus if the alkalinity was at
60, you add that acid in there,there's no real buffer in the
water.
I'm just trying to get a handlearound the fact um adding
cyanaric acid to the equationwith the chlorine effectiveness,
um, but I also want to also umsee if the alkalinity level
could also be a factor when youadd that much acid to a pool.

SPEAKER_02 (11:40):
Okay, I I understand what you're asking.
Um so alkalinity, we've got tothink of it as just a kind of a
how much sort of question, asopposed to pH, which is an
equilibrium that's kind of likea seesaw or it's it's a balance
and it's constantly moving.
Alkalinity is much more easy tocontrol and to predict.

(12:01):
So if you have a hundred partsper million alkalinity, when you
measure total alkalinity, itincludes things like hydroxide.
Sorry, uh it includesbicarbonates, it includes
carbonate alkalinity, itincludes cyanurate alkalinity,
which is what needs to beremoved in order to get to the
carbonate alkalinity for theLSI.

(12:23):
Uh things like boratescontribute to the buffering
capacity, even phosphates couldcontribute.
And the last two are in asmaller amount, but they still
are significant enough that youcan manipulate your pH up and
down.
But there's a differentbuffering agent that nobody
talks about.
And that's because it doesn'tbuffer pH directly, but it does

(12:43):
buffer the LSI, and that'scalcium hardness.
People don't appreciate calciumhardness, but in reality, it's
probably your best friend,provided it's not off the charts
high.
Um provides you a greatfoundation for a steady
saturation index because itdoesn't move.
Like uh, if you ever look at theback of a TUMS, like if you ever

(13:05):
take had indigestion and youtake those little tablets of
Tums, the key ingredient iscalcium carbonate.
And at the end of it, you know,dot dot dot dot dot, antacid.
So calcium carbonate is anantacid.
Well, that's what alkalinity is,it neutralizes acids.
So when you're trying to saylower your pH from 8.0 to 7.5,

(13:27):
your alkalinity determines howmuch acid that takes because you
have to burn through more of itif the number's higher.
So for instance, uh, I'm gonnado it on the Arenda app right
now while we're on the phone,and I'm gonna set a 20,000
gallon pool from 8.0 down to7.5, and I'm gonna start at 80

(13:49):
alkalinity.
At 80 alkalinity, it takes 28.02ounces of myriatic acid.
28 ounces.
At 90 alkalinity, it's 31.5ounces.
So now you've gone up anotherthree ounces.
At 100 alkalinity, it's 35.02.
And so you see the higher youralkalinity, the more acid it

(14:11):
takes to do the same pHcorrection.
That's because you have more ofa buffering capacity you have to
burn through in order to dothat.

SPEAKER_00 (14:18):
Got it.

SPEAKER_02 (14:19):
Yeah, so you're you're absolutely right.
But the pH bounce, like bouncingback, this is my opinion.
This is not Arenda's opinion.
This is uh just kind of a gutfrom what I've heard from
customers.
I don't think the bounce isbecause of the alkalinity.
I think the bounce is becausepeople aren't adding acid

(14:39):
properly, because it's plungingto the bottom of the pool.
It's etching, it's pulling out a12.6 pH calcium hydroxide, and
that's the cause of the bounce.

SPEAKER_00 (14:50):
And if you're looking for more podcasts, of
course, just go to my website,swimmingpoollearning.com, click
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That'll take you to a drop downmenu of over 1800 podcasts there
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Thanks for listening to thispodcast.
Have the rest of your week andGod bless.