Low Cya -> Lo Cl, and Hi Ch Questions

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Posts: 8
Joined: Thu 29 Apr, 2010 09:55
My Pool: 33k gunite, salt, sta-rite system 3, floor system
Location: DFW TX

Low Cya -> Lo Cl, and Hi Ch Questions

Postby acroy » Fri 30 Apr, 2010 10:43

I bought a house with a pool last year and am learning up on it, largely courtesy of this great forum! :D

Here is my pool (using test kit recommended on this forum)
• Problem: pH rise, low CL, hi CH
• FC: 1ppm
• TC: 1ppm
• pH: 7.8
• TA: 80
• CH: 440
• CYA: 40
• My pool: gunite, 33k
• Pool chemicals: pool acid…
• My pump & filter: 1.5&1hp pumps, DE system
• Other info: 72f, 4hrs/day run time, water is crystal clear and feels great to swim in

2 things jump out:

Low CL:
Obviously my CYA needs to go up. I don’t run the pool much as spinning those pumps are expensive. The water is beautiful and clear. There’s a lot of organic matter blown in all the time, I try to keep it reasonably clean, but it’s a struggle. I’m looking at replacing the old motors with maybe one big 2spd or vfd motor (different thread), then the run time will go up and salt cell should drive up CL.
-once CYA is adjusted up the pH rise should slow as well, correct?
-TA of 80 OK or should I try to reduce?

440ppm. No scaling is evident and I control the pH. Municipal water is around 120ppm (not used any makeup water yet). Hardness was right at 400ppm in Oct, we got 20inches of rain since then (pumped it out), I was expecting CH to go down but it’s creeping up.
-does the salt content throw off the CH test?
-can I get away with 440ppm if pH is okay?
-any chemical way to pull down the CH?
-Pool was re-plastered in 2007 – might this be still driving it up?


33k gunite, Clearwater salt, 1.5 & 1hp pumps, floor return jets, fountain, System3 DE, Dirt Devil ProV vac, borates. Soon: efficient pump(s), robot cleaner...
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2381
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Low Cya -> Lo Cl, and Hi Ch Questions

Postby chem geek » Sat 01 May, 2010 08:33

Let the TA get a lower as that will help reduce the rate of pH rise (and yes, the higher CYA will help that somewhat as well but won't reduce the amount of acid needed -- only lowering the TA will do that, assuming the pH rise is coming from carbon dioxide outgassing). Your higher CH will let you have a lower TA with no problem.

And yes, your Free Chlorine (FC) level is too low, even for the low CYA level you have now. Please read the Pool School for more info.

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