traugh, if you haven't read up on CYA here to stabilize your chlorine, do..i've got mine at 60-80ppm..my cover has been off since sunday...sunday to wed it was sunny and 28-30C...today was rainy and 15...i shocked on sunday to about 20ppm..i'm down to 15ppm after going through the weather gamut with the cover off and tomorrow night it will still be way higher than i need it (now that my algae has cleared up..i'll pretty much put money that if i had used bleach and no CYA, 3 days into that heat and sun, my chlorine would have at best been 5ppm..that is how effective CYA is to "sunscreen" your chlorine..i'm itching to try my new chlorine generator installed tuesday, but it's no point until levels are normal..sigh i expect by sunday..one week since i shocked, they will be down to what i want...