Chlorine Demand


New member
Jun 25, 2018
ooltewah, tn
Fist time posting to this forum. i know questions about chlorine demand have been asked 1000 times but reading the threads has left me confused. Here is my situation.

40,000 gallon plaster pool with Hayward t-15 turbo cell and Aquarite 900 control panel. The pool was drained this year and fresh water added back in May.
CYA - 40
Ph - 7.5
Alkalinity 100

Here recently, I would say in the past 3 weeks, I have trouble maintaining Chlorine. Around that time I had a high combined chlorine level so I calculated breakpoint chlorination, added the appropriate amount of chlorine and now FC = TC, so no combined chlorine present. Running the t15 cell at 100% barely maintains .5-1.0 FC in the pool. Overnight it will creep up to 2.0-2.5 in the morning, but by afternoon back to .5 - 1.0. I have been adding 12.5% liquid shock daily to maintain adequate FC levels. No algae present, phosphates are high a 3000. I do my own testing with a commercial Taylor pool testing kit.

Thanks for any advice on how to trouble shoot this. Very frustrating and getting expensive.
Thread Status
Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.