Great forum! Thanks for the help!! I am hand dosing 10 % chlorine. Our pool is in the sun. I am confused as to why I want the CYA at 30 or above. If chlorine is more efficient with low CYA... it seems that keeping the CYA low at maybe 10 or 15 will use more chlorine due to sun but since it is more efficient at low CYA levels is it a wash since it the amount required for acceptable FC will be far less overall? I really don't want to end up with high CYA and go through draining again. The next bazillionaire is the one who comes up with lowering CYA without draining and replacing water.