Zero CYA???

Uncle Ben

Well-known member
Apr 20, 2010
Southern California
Went to a nearby pool store for the first time to get a full set of numbers. My kit does not test for CYA, but I added it based on the directions on the CYA bottle and I added 4 pounds, which was the full bottle. Since then I have probably only replaced around 6" of water in the pool. Anyway, the guy at the store said I have ZERO CYA, which does not seem possible to me, based on the fact that water replacement is the only way to lose CYA, and I have not replaced very much.

So is it even possible that I could really have no CYA at all?

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
San Rafael, CA USA
It's very unlikely. There is a way for the CYA to go away, but only if your Free Chlorine (FC) level went to zero and bacteria converted the CYA into ammonia (and intermediate chemicals on the way from CYA to ammonia). If that happened, you'd have a very high chlorine demand and a zero FC reading.

The most important advice given on this forum is to get yourself a good test kit such as the TF-100 or the Taylor K-2006. Without a good test kit you are simply shooting in the dark. A proper test kit will pay for itself many times over in chemical savings and in the time saved from not having to fix problems with the pool. Pool stores are notorious for giving incorrect test results, especially for the CYA test, and using test strips often gives the wrong CYA reading as well. Please, please get yourself a proper test kit.


Well-known member
Aug 1, 2010
I second that. Sadly I only have test strips. I've added enough Trichlor without backwashing to have 40ppm CYA yet the strips show nada.