Sometimes confused with pH, has nothing to do with pH level. Alkalinity is due to the presence of bicarbonate, carbonate, and hydrate ions. For our purposes alkalinity consists of calcium and magnesium bicarbonate. This alkalinity will produce CO2 when water is heated; therefore, it can cause corrosion even though the pH is neutral. Usually alkalinity as high as 300 ppm is not a problem unless the hardness is below 10 gpg. An index called the saturation index is used to determine if a specific water will cause corrosion.