are you testing the pH with the chlorine that high? If you are you are probably getting bogus pH readings. The Phenol red indicator for pH will give false high readings when the chlorine levels are above about 10 ppm (some cheapie kits it might be even lower. Pentair is one of them!) Don't test your pH until the chlorine is near normal levels and see if that helps. There have been many posts on the forum discussing this so I will not go through the chemisty of what is happening again.