Right now it's at 40, and by what I've read, that should be ok. I'm adding 1/2 to 1 full 187oz bottle of bleach at least every day. Should I have higher CYA levels because of the full sun (8am-7PM) My pool is blasted by full sun all day and the temp got up to 94 last Sunday. I plumbed up an evaporator last Sunday evening and dropped it 12 degrees in two evenings. Not to get off my original question, but somehow my stuff seems to work backwards. Everyone says the evaporation (cooling) process works better during the day (humidity and all that jazz) but mine actually heats at least 2 degrees while running during the day, while when I run it at night it cools at least 6 degrees, sometimes 8 a night.