Optimum CYA level

Aggie_ChE

Bronze Supporter
LifeTime Supporter
Apr 30, 2011
7
Longview, TX
We live in Texas and have an outdoor 16,000 gallon vinyl lined pool. What is the optimal CYA concentration to shoot for? Typically I aim for 40 ppm CYA just because 40 is in the middle of the 30-50 ppm target range. This seems like a too-simple reason to target 40 ppm; hence my question. Maybe I should add CYA only to 30 ppm so I can keep the free chlorine target a little lower at 4-6 ppm? Every spring I have to start over on CYA, as testing shows that apparently over the winter I lose the CYA. Since I have been using the BBB (bleach, borax, baking soda thanks to TFP) method for years, dialing in the CYA level is pretty simple. Will one CYA level help keep my water in better shape while maybe requiring less bleach than another CYA level? (I have been adding my bleach through a HASA Liquidator for years. The Liquidator works GREAT!) Thanks for your help.
 

djdonte

Well-known member
Mar 25, 2019
152
Houston, TX
30 requires less FC to do the job but in the summer the sun eats too much chlorine, at least in the Houston sun. I keep it 40-50, favoring 40 to allow for using pucks while I'm on vacation. In the cooler months I let the CYA drift down as well. Do you use powder CYA or trichlor pucks to get your CYA up?
 

Aggie_ChE

Bronze Supporter
LifeTime Supporter
Apr 30, 2011
7
Longview, TX
Your sun and mine are probably similar. Northeast Texas is hot and humid, but not as humid as Houston. I use the CYA granules. I have the larger 8 gallon Liquidator which give me about a week's worth of bleach for vacations. It seems like I need about a gallon of chlorine per day which seems more than most people on TFP. Thanks for your reply.
 

djdonte

Well-known member
Mar 25, 2019
152
Houston, TX
How many gallons is your pool? Set your signature up to make it easier for people to help you in the future. If you are sure the chlorine doesn't have anything to eat, then perhaps time to up the CYA. I use about a gallon (of 10%) every 2-3 days which translates use 2-4 FC/day in the sun depending on cloud cover and bather load.
 
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Aggie_ChE

Bronze Supporter
LifeTime Supporter
Apr 30, 2011
7
Longview, TX
Thanks for the suggestion on the signature. I just updated. My pool is about 16,000 gallons in direct sun all day. I have thought about it but have never run a free chlorine demand test. I guess I should do the test. You sure use less chlorine than I do.
 

djdonte

Well-known member
Mar 25, 2019
152
Houston, TX
Yes you should. I was using 5-8 a day and a few more a night after a half assed slam thanks to HEB lowering their chlorine content. I had to slam my pool hard for about a week to pass the OCLT and get rid of CCs. No problems since. I have the house on one side and trees on the other so I don’t get direct sunlight all day but most of the day and during the hottest times.
 

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