Balancing CYA - need feedback


LifeTime Supporter
Mar 28, 2007
Houston, TX
So it appears my PB put way too much CYA in my new pool. Multiple tests are coming back at 110. I have been keeping my FC north of 5ppm but would prefer not to have to leave it up there. I need some confirmation on my thought process on lowering my CYA.

Its currently at 110 and I want it to be at 75 as recommended by my SWCG. 75/110=.68, 1-.68 leaves .32 or 32% of fresh water required to lower my CYA down to 75. Is my thinking even remotely correct?


Mod Squad
TFP Expert
Apr 4, 2007
SW Indiana
Yes. Usually easier and safer for the pool to drop it in increments of 10% or so. First cycle will drop CYA 10% or 11ppm. Second cycle will drop CYA 10% or 9.8ppm. Third will drop it 10% or 8.9 ppm. That will get you to about 80.


In The Industry
Mar 29, 2007
Knippa, Texas
Use the "sheet method"; cover the pool with a plastic dropcloth and start draining while running fresh water from the hose on top of the sheet. The sheet keeps the fresh water from mixing (much) with the old.

That way you don't significantly lower the water level while replacing your water.