thanks for the help, no trees around pool closest ones are 75 ft away. on the cya it is around 65-70. ph usually stays around 7.2- 7.5. i use the t-100 test kit. I think that is what it is called it is the kits that everyone here recommends. it does want to start in the corners that seems to get most shade in afternoon as sun sets behind house. this last time we went on vacation for 7 days and i put solar cover on it to help keep water from evaporating when i came back had it in several spots mostly still in areas that got some shade during day(shadow from diving board, slide, etc) and the corners. it had started to spread to more spots. once i brush walls and floors it comes off with no problem. i use an automatic cleaner and it will pick up most of it . I thought maybe cleaner was spreading it so last time i shocked pool i left cleaner in pool to make sure it got all algae. My overnight test came back good and then once we go 3-4 days with no one swimming it will just start in corners . Not alot but enough you can notice it. If my chlorine levels are good how can it keep coming back??? I have tried raising levels to 9-10 and it seem to help a little..... What would be highest chlorine level that i could run pool at with out any issue with swimmers or equipment????
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