Quote Originally Posted by tphaggerty
Well, here in NY the rain is pretty acidic. We had about 1" (or possibly more) of rain during that same period (which on a 20x40 pool is about 500gals). Does that work?
Yup, that could do it if the rain were particularly acidic. You would have needed the rough equivalent of 4 cups of Muriatic Acid to go from 7.6 to 7.3 in a 24,000 gallon pool (my rough estimate from your 500 gallon, 1" number, assuming average depth of 4 feet and assuming a TA of 100). 4 cups of Muriatic Acid in 500 gallons of pure water would make the pH of about 4.

Richard