CYA/Chlorine - Angry pool store guy

jseyfert3

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Bronze Supporter
TFP Guide
Oct 20, 2017
1,967
Southern WI
Pool Size
15000
Surface
Vinyl
Chlorine
Liquid Chlorine
So, chemistry is NOT my strong suit. Perhaps @JoyfulNoise can chime in here too, and/or move this over to The Deep End.

in the first reaction wouldn’t the H+ and Cl- combine to form HCl (and its sequelae — probably irrelevant to this discussion but just proving I’m paying attention)?
No. HCl itself disassociates when added to water into H+ and Cl-. This addition of H+ is how the pH of the water is lowered when you add muriatic acid, aka hydrochloric acid, HCl.

The H+ ions form hydronium ions, which Wikipedia can describe better than me.

pH is a measure of how many hydronium ions, usually denoted as H+(aq), are in the water. So anything that adds H+(aq) will lower the pH of the water.

Well, at least anything that doesn’t add an OH- or other base at the same time. The addition of OH- will combine with H+(aq) to form H2O, and the resulting reduction in H+(aq) will raise the pH. So adding a strong base like NaOH, which will dissociate into Na+ and OH-, will result in sodium ions floating around and less H+(aq) and a higher pH. The opposite of how the addition of HCL will result in chloride ions and the addition of H+(aq) and a lower pH.

Part of me wants to suspend a bunch of sodium hydroxide over concentrated hydrochoric acid and then drop it into the acid. While standing WAY back of course. For science…

What eventually happens to the Cl- ions with all the other stuff available in the water?
Nothing. They just sit there until removed via water exchanges (or reverse osmosis). Chlorine, being a halogen, desperately wants another electron. This is what makes it such a powerful oxidizer. Once it has this electron and is Cl-, it’s happy, stable, and very unreactive.

I think this is what makes table salt, sodium chloride, such a stable compound. The chlorine wants an electron. The sodium has an electron it doesn’t want. So they are happy together after sodium give an electron to the chlorine.

Doesn’t sunlight change some of this?
No. Sunlight, or more specifically the UV in sunlight, causes the HOCl and OCl- to breakdown, just as if they had oxidized some organic waste in your pool. This “wastes” the FC in your pool. But doesn’t change how the chemistry as a whole works.

Chem geek talks about how sunlight breaks down FC in that link I posted as well.
 
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jark87

Silver Supporter
Jun 5, 2011
945
Flower Mound, TX
Pool Size
25500
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
Like the OP, I will occasionally have my local Leslie’s test my water only so that I can verify my CYA “guess”. Fortunately, the staff there is pretty good and they don’t argue with me when I explain why I keep my FC above 4 and TA below 80.

If the pool store guy that was referenced truly had 30 years of experience, I fully believe that the dot test is a trigger and he has been overexposed to it. I hate the dot test….
 

darkrider

Well-known member
Jun 14, 2021
261
North Atlanta
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Aquapure 1400
Many years ago (late 80's/early 90's), my first job was lifeguarding at a large commercial pool that used chlorine gas. Talk about some nasty stuff! We had a leak once, and it literally knocked the person out who opened the door to the pump room. He never even made it into the room! He must have been down for a good 3-5 mins, and it's amazing he didn't have any lasting effects other than severely swollen eyes, nostrils, etc.

My 2nd lifeguarding job was at a hotel pool during college. They had indoor and outdoor pools, and both used highly concentrated Liquid Chlorine in 5 gallon jugs that we had to pour into an even bigger vat. That was always fun, since it was virtually impossible not to get some splash back. The vat was on a constant pump that just had a dial to set the rate, and I'm guessing no stabilizer. We used a Taylor test kit to check pH and CL hourly in the summer, and every couple of hours in the winter...

Thinking back, I guess that also means I have 30 years experience! :ROFLMAO:
 
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jedigrover

Gold Supporter
Sep 13, 2010
330
Plano, TX
Pool Size
21000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Like the OP, I will occasionally have my local Leslie’s test my water only so that I can verify my CYA “guess”. Fortunately, the staff there is pretty good and they don’t argue with me when I explain why I keep my FC above 4 and TA below 80.

If the pool store guy that was referenced truly had 30 years of experience, I fully believe that the dot test is a trigger and he has been overexposed to it. I hate the dot test….
When they ask why your chlorine is so high, tell them you have black algae and the black algaecide that you just put in said to shock the pool. It will give them a reason to believe your chlorine should be that high, and tell them that you've already used an algaecide so no use in trying to sell you one...but give them hope that maybe you'll come back in a week, when they're sure that will fail.
 

TampaKathy

Gold Supporter
Oct 2, 2020
793
Tampa, FL
Sometimes I go to my local store to get my water tested as well. Mainly because until recently I also didn’t trust my ability to interpret the CYA test. I always make sure to buy something that I actually need or would be good to have on hand in case of an emergency (glue for vinyl patch, or epoxy for example). I listen intently to their advise, (because they might catch on if I don’t) and then I tell them I already have whatever chemical they are trying to sell me. “What’s that you say? I need to add algicide? Good thing I’ve got 38 gallons of algicide at home!” (It’s fun telling them you already have a ridiculous amount of whatever it is they are trying to sell you)
I do this too...oh, thanks, yep, I happen to have those chemicals at home already, lucky me!
 
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ghall6292

Bronze Supporter
Jun 10, 2018
265
North Central PA
Pool Size
13500
Surface
Vinyl
Chlorine
Liquid Chlorine
Just received a new "Summer Sale" catalogue in the mail from a well-known online retailer. The first 15 pages were nothing but chemicals and magic potions!

My old pool PTSD almost kicked in until I took a break and skipped to the "fun" stuff: accessories, toys, hardware, nice-to-haves, etc. If you should receive the same catalogue, and your PPTSD allows it, just look at all the junk that an uninformed pool owner could dump into their pool!

So far this year, I have added liquid chlorine, stabilizer, 20 Mule Team Borax, and, oh yes: water. I anticipate at some time in the future some muriatic acid will be needed. That's four things (not counting water.)

THANK YOU TFP!
 

SR56

Member
Feb 8, 2020
16
Orlando, FL
Pool Size
14100
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Jandy Truclear / Ei
I really hate that black dot test. Honestly, I hate most of them because I'm colorblind. Without my girl here to tell me when something changes color I'd be screwed. I think the FC and salt tests are the only ones I get right since I can sort out clear vs red and milky vs brick red.
 

TampaKathy

Gold Supporter
Oct 2, 2020
793
Tampa, FL
I came up with a layperson example for TDS.

You have 37 things in your fridge, do you have enough food for the week ? Well that really depends on how much and of what you have in there, now doesn't it ?

*prompted me to check my fridge and I had 51 things on the door alone.
Yesterday I looked at a bottle in my fridge...expired in 2016...the best part is we moved 2x in 2019 so back in 2019 I apparently thought, oh, it's only 3 years past it's "best by" date, sure, let's take this with us. :)
 

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Yev

Well-known member
Jul 29, 2014
556
Independence, KY
I am against Pool Store Guy, and that person has never done me anything truly helpful.

But one thing to keep in mind, many of these people don't even own a pool, they are just employees. They are saying/preaching information that has been explained to them as fact. The more experience, the more indoctrination into the method, so that 30 years is not 30 years of learning, its 30 years of being indoctrinated into the same method. Sure an owner of a manager of a pool store might have financial incentive to sell you extra stuff, but Jon behind the counter who has worked there for 10 years, he probably gets paid by the hour, or a salary, and is trying to be helpful based upon the training he has received. The inaccurate ressults, not like he is trying to lie about the results, his machine simply gives him numbers, and then has a chart that says what to do based upon the numbers. Lucky we all know better, but just remember that not everyone is intentionally evil, though many (as in the OP original case) are jerks with no manners.
 

Mdragger88

Bronze Supporter
TFP Guide
Jun 1, 2018
6,524
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
The interesting thing to me is that my local store sells liquid chlorine as a courtesy basically because they have a pool service & that’s what they use but I have never seen them tell someone to use it - only trichlor/dichlor & cal hypo as of late along w/ floc. & of course mps for those salt pools 🤣
I think they know I know their secret 🤫
 

PennyPool

Member
Jun 6, 2014
18
Baton Rouge, LA
Pool Size
34000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-15
Sometimes I go to my local store to get my water tested as well. Mainly because until recently I also didn’t trust my ability to interpret the CYA test. I always make sure to buy something that I actually need or would be good to have on hand in case of an emergency (glue for vinyl patch, or epoxy for example). I listen intently to their advise, (because they might catch on if I don’t) and then I tell them I already have whatever chemical they are trying to sell me. “What’s that you say? I need to add algicide? Good thing I’ve got 38 gallons of algicide at home!” (It’s fun telling them you already have a ridiculous amount of whatever it is they are trying to sell you)
I keep an excel spreadsheet of my levels so I can see how they fluctuate and try to determine what is causing it. When I do bring a sample to a pool store, just to see, and they tell me my CYA is 30 I just pull out my spreadsheet and say that is amazing because it has been fluctuating between 70/80 for a least the last week or two. Oh, and I have plenty of stabilizer at home. 🤣
 
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