[Treatment process] pH correction [Contaminants Removed/Altered] Usually does not technically remove anything; alters water chemistry-except via air stripping (see below). Controlling low pH often reduces levels of leached copper and lead in plumbing systems. [What it does] 
By dissolving an alkaline (basic) material into water, low pH (<6.5 units) can be adjusted to prevent corrosion. Often accomplished with a calcite filter/contactor which uses clean lime to correct pH. Sometimes high pH's are controlled by acid injection. This may be done for scale control, though very seldom in our service area.