Quote Originally Posted by tphaggerty
Ha! That explains why my PH was low after leaving the solar cover on for 4 or 5 days last weekend when we were out of town. I have an SWG and my PH stays rock steady at 7.6, except this weekend, when it was somewhere between 7.2 and 7.4 (I have trouble seeing the colors that well).
Well, now you've introduced another mystery. Something introduced into your pool is apparently acidic so that when you have the cover off with carbon dioxide outgassing this compensates so you have no net gain in pH. But that still leaves the question of what is driving your pH DOWN when the cover is on. I have no answer for that one! Anything unusual about your pool that could explain this?

Richard