CYA Mystery


Jun 9, 2008
Avon Park, FL
About a month ago, I had water tested at Pinch A Penny and they said my CYA was around 90 or a little higher. I took out the tablets and haven't used them since. I had an algae problem a few weeks ago and got it cleared. I also recently purchased a SWG and got my new TFTest Kit in today. When I took the sample for CYA, the black dot never disappeared which means the CYA is low. How could it have dropped so low already. I know I did the test right.

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
Since you know you did the test right it's really low.
We've been having several posters with CYA mysteriously going to zero this year.
We know that there is a bacteria that converts CYA into Ammonia but we don't fully understand the particular instances when this happens. A leak with a lot of refill will also drive the CYA down a lot. This is most common with an autofill where it adds water without the owner realizing it.

That and Pool Store CYA tests are notoriously inaccurate.


Bronze Supporter
LifeTime Supporter
Oct 6, 2009
Nazareth, PA
LOL..good one Folsom!!!

I actually (for kicks) brought a water sample to my local pool store the other day and - just as this post suggested - the CYA level they gave me was VERY wrong. I've been consistently getting a reading between 50-60 and they actually told me it was 30.