Newbie needs opinion on CYA levels after rain


Apr 7, 2020
Salisbury, NC
Hi And thanks in advance for help. My pool is new to me and I’ve taken over this year from a pool service. Opened the pool with a SLAM and your help and all going fantastic. After drain and refill of half the pool CYA levels were at 80 to start and I planned to do another drain and refill again at some point. Here in NC we had a ton of rain in the last 2 weeks. Twice the water in pool was above the skimmer and I had to drain about 2-3 inches off the pool. So a total of maybe 4-6 inches. Now my CYA level is reading 55. This is good news, I get that, but that much of a drop? Weird right? Any thoughts?

Today’s levels : CYA 55 ( half way in between 50 and 60)
FC 8 pH 7.6 TA 70 CH 50 (vinyl pool liner)


Gold Supporter
TFP Guide
Jun 8, 2019
Milwaukee, WI
It is strange, but the test isn’t perfect and CYA can degrade over time too. Just not usually very quickly.

If you are getting a reading between 50 and 60, round up and call it 60.