CYA value higher AFTER draining 2/3 of pool

Nov 20, 2018
Newnan, GA

We are hoping someone can shed a light on an issue we have with our CYA.

Oct 1 - Water tested by local pool store CYA = 128

Nov 15 - Water tested by our local pool maintenance company using their Taylor test kit = CYA too high to get a value

Nov 15 - Water tested by local pool store CYA = 136

Last week we drained 2/3 of the pool --- about 22,000 gallons. We refilled the pool with local tap water. Nothing else has been added. The pool company says the CYA using their Taylor test kit is too high to get a value.

My husband and I purchased a Taylor kit 2005C. We tested the CYA and it looks over 150.

How can the CYA be higher after draining 2/3 of the pool?

The local pool company wants us to completely drain the pool this week 33,000 gallons and pay for them to acid wash it. Bye the way calcium hardness is fine and there are no stains in the pool. The pool was built in 2004 but the pebbletec finish is very nice.

Has anyone else had this situation?

Kind regards,

Stephanie in Newnan GA

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Hi Stephanie. Simply put - probably poor testing before. Since there is no stabilizer in local water, CYA will not increase unless you add it - either directly or as a byproduct in items like bags of shock and/or chlorine tablets (pucks). Your sig shows the inline chlorinator. Are you keeping that stocked full? If so, that's part of the problem. As for the pool store tests, you can just about ignore them all. Pool store CYA tests are horrible and almost never produce an accurate CYA test. It's good you ordered your own K-2006 test kit (according to your sig). Use that once it arrives and base your water exchanges (if any) on those results.
CYA Testing:
Proper lighting is critical for the CYA test, so you want to test for CYA outside on a bright sunny day. Use the mixing bottle to gently mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then gently mix again. Recommend standing outside with your back to the sun and the view tube in the shade of your body at waist level. Then, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. Once it disappears, record the CYA reading. To help the eyes and prevent staring at the dot, some people find it better to pour & view in stages. Pour some solution into the viewing tube, look away, then look back again for the dot. Repeat as necessary until you feel the dot is gone. After the first CYA test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, gently shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate your own CYA reading. Finally, if you still doubt your own reading, have a friend do the test with you and compare results.


Bronze Supporter
May 20, 2018
Clovis, CA
Easy -- pool store results were horribly inaccurate, as would be expected from a pool store. They are often inaccurate at high CYA levels (err... at all CYA levels).

The pool maintenance company should have been able to perform the test using the dilution method. There is no excuse for them to not know about that, other than they don't know what they are doing. In your case probably mix 1 part pool water with 3 parts tap water, then multiply CYA result by 4.

Acid wash? Is there a reason why? CYA is not one.

See what you get with your own kit, then consider a new pool company, or even better, learn the TFP method, because if you want it done right, you do it yourself.

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
You got two good readings that would explain what happened.
Water tested by our local pool maintenance company using their Taylor test kit = CYA too high to get a value
It's not uncommon for CYA to be 400 or higher in a tablet fed pool, so draining 2/3rds of it would still mean that it's over 100 and possibly as high as 200.

I don't see any reason to completely drain it and have it acid washed.

I'd say just drain another 1/2 and see where that gets you to.