The primary way to treat the problem of low pH water is with the use of a neutralizer. The neutralizer feeds a solution into the water to prevent the water from reacting with the house plumbing or contributing to electrolytic corrosion; a typical neutralizing chemical is soda ash.
Alkaline water is generally is harmless until it is too high Add sulfur, phosphoric acid or a pH-lowering solution lower the pH if the pH is too high