Brown stains on a Pebbletec finish, that go away when you raise the chlorine level, but can't be brushed off?
Is that right?
If it is, I'm stumped. Are the stains distinct enough, to show up in a photo?
Regardless, you need a good test kit -- pretty much everything starts with accurate testing . . . though I can't promise it will help with the stains. Anyhow: http://pool9.net/tk/
It's pretty common for pools with an SWCG to experience a constant slow pH rise: it's an effect of the SWCG. Higher borate level will make it easier to control. Using muriatic acid makes it fairly cheap to manage: http://pool9.net/ma/
. . . membership updated.
Bookmarks