I was keep my pump off for almost a week because I tried to figure out where the slow leakage is. So within the week, I kind of replace 2-3 inches of water. (The pool averagely is about 5 feet deep). My CYA level was 37 one week ago, and today it is 22. (FC is almost 0 and CC is 1. Ph & TA are good). I thought that CYA won't be decreased unless water is replaced. But how can my CYA level drops dis-proportionally? (btw, my pool has full sunshine. and during this week, long island has been pretty hot. >80F with everyday being sunny.) (The test result is from one of the local pool store and should be pretty accurate.)
One more question, for my case, do you think I need to shock the pool once? the water is pretty clear btw.