I know this has been covered many times before. I have an in ground fiberglass spa that turns bright white after the water is emptied out and it dries. I circulated 5 pounds of citric acid through the pump system for two weeks and nothing. Next was 15% muriatic pool acid from HD applied full strength. Nothing. It did not fizz at all.This seems to be the kind of white that is like water spots on a window. When they are wet they disappear and after they dry out they turn white. Should I try the 31% muriatic acid from HD next? Running out of ideas now. Thanks for any help!
