When I close my pool I do raise the chlorine concentration to about 8ppm. However I use bleach as my only source of chlorine. During the season, my pH never needs adjusting. Well that is once I get it right at opening. But my point is that bleach does not affect my pH over the course of the swimming season so I would not think it would affect the pH over the winter. The only thing I can think of is the water on top of my cover. I need to check into that.

Thanks for the information.

Jim