The Environmental Protection Agency (EPA) recommends drinking water to be at pH 6.5 – 8.5. It is important to maintain drinking water within the safe range as pH influences concentration of certain contaminants.
If the pH is low (acidic), you get “soft” water. This will cause corrosion in the metal water pipes, and will pose a major health risk.
At higher pH (alkaline), the water is “hard”, which will result in the building up of lime scale, and may cause blockages in pipes. This may also destroy appliances like washing machines or dish washers.
Another parameter to test for is Total Dissolved Solids (TDS).
TDS basically refers inorganic salts and small amounts of organic matter that are dissolved in water. The principal constituents are usually the cations calcium, magnesium, sodium and potassium and the anions carbonate, bicarbonate, chloride, sulphate and, particularly in groundwater, nitrate.
The U.S. EPA sets the maximum contaminant level for TDS at 500 ppm. At higher levels, gastro-irritations, excessive hardness, unpalatability, mineral deposition and corrosion may occur.