Quote Originally Posted by r-brian View Post
The one thing that never seems to come up is what is the pH of your water to begin with.
Perhaps because the pH of the water is rather trivial, especially compared to the acidity of an acid stop bath. And when I use the term "acidity", I'm referring to the amount of acidity that is available in the stop bath to neutralize the base in developer.

Whether your tap water is pH 6 of pH 8, it may have very little buffering capacity and have a negilgible effect on the neutralization on the developer other than merely diluting it. Of course, a pH 8 water can't "neutralize" the developer as it has no acidity.

Bill Troop recommends using a buffered stop bath for a high efficiency stop. It consists of acetic acid and sodium acetate combined to make a buffered solution which has moderate pH that is around 5, but it has a very large amount of acidity with which to rapidly neutralize the pH of the developer and stop development very quickly.