CYA Life Span

What is the expected life span for CYA? How long should it last before I need to add more CYA?

I have a Taylor test kit and find it hard to read CYA. I filled up the CYA test window before it really became cloudy enough to obscure the black dot. No reading here, but it is less than 30. I have added some CYA about a month ago but it appears my CYA has dropped back down.

Any advice is appreciated, thanks!

FC = 2
TC = 2
Ph = 7.6
TA = 80
CH = 220
CYA < 30


Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
Tucson, AZ
Generally the CYA does not get "consumed" and is only removed from the pool due to splash out / backwashing water replacement. There are some reports of the CYA disappearing over winter in a closed pool, but that does not sound like the case here.

How high was the CYA previously? Note that the test is only good to about +/-10ppm and lighting conditions can affect the test results. More info on the test can be found here: extended-test-kit-directions-t25081.html#p206397


LifeTime Supporter
TFP Guide
Jun 12, 2011
CYA stays in the water and it is only removed by draining or splash-out. It is very slow to dissolve and can take a week to show up on tests. The only time I have heard of it dropping is over the winter when the pool is closed. Be very careful not to add too much or you will be draining water to get rid of it. Use the Pool Calculator to determine how much to add based on your current level and pool capacity. Proceed with caution!

Wow, you guys are fast!


TFP Expert
LifeTime Supporter
May 10, 2010
SW Louisiana
CYA does get consumed even in a well balanced pool, but is a very slow process, loss due to back washing, splash out, and rain dilution are likely far larger factors in lowering CYA for most pools. I notice it only because I have an indoor pool where there is no rain dilution and maintain chlorine balance even in the off months when the water is too cold to swim, in general I will see around a 10 ppm CYA loss over the winter non swim season (this has been fairly consistent every year for the last 3-4 years that I have been closely tracking CYA) .

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
Do you have an auto fill that may be masking a leak. A leak will dilute the CYA as you're actually leaking it out of the pool.

Also check the CYA container. There was some posts about 50% CYA. So unless you tested it after ouy added it may not have added as much as you think it did.


Well-known member
May 9, 2008
NE Florida
My CYA goes somewhere every winter in Fl. I usually finish the season at about 40-50. In winter I circulate the pool and don't do much but keep the Cl and pH balanced. The becomes a mess in tree season from Feb-April, then I go crazy to get ready for spring. My CYA is consistantly "0" after winter. So in certain pools it gets consumed or deteriorates somehow.