Code
Total alkalinity shall be maintained in the range of 60 to 180 PPM (mg/L).
Annex
Total alkalinity is closely associated with pH, but rather than a measure of hydrogen ion concentration, it is a measure of the ability of a solution to neutralize (buffer) hydrogen ions. Expressed in parts per million (PPM), total alkalinity is the result of alkaline materials including carbonates, bicarbonates and hydroxides - mostly bicarbonates. As noted in the MAHC, the ideal range is 60 PPM to 180 PPM. This acid neutralizing (buffering) capacity of water is desirable because it helps prevent wide variations in pH (pH bounce) whenever small amounts of acid or alkali are added to the POOL. Total alkalinity is a measure of water's resistance to change in pH and is a source of rising pH itself from the outgassing of carbon dioxide.
Too Low
If total alkalinity is too low: pH changes rapidly when chemicals or impurities enter the water. pH may drop rapidly when using net acidic sources of CHLORINE or other acidic chemicals (e.g. Trichlor (trichloro-s-triazinetrione), Dichlor (sodium dichloro-s-triazinetrione), potassium monopersulfate), causing etching and corrosion.
Raising Total Alkalinity
Total alkalinity can be raised by the addition of bicarbonate of soda (sodium bicarbonate, baking soda). 1.4 lbs. bicarbonate of soda per 10,000 gallons (635.0 g per 37,854.1 L) will raise total alkalinity approximately 10 PPM.
Too High
If total alkalinity is too high: pH becomes difficult to adjust. High pH often occurs causing other problems such as; cloudy water, decreased disinfectant effectiveness, scale formation, and filter problems. The higher the total alkalinity, the more resistant the water is to large changes in pH in response to changes in the dosage of disinfectant and pH correction chemicals. If the total alkalinity is too high, it can make pH adjustment difficult.
Lowering Total Alkalinity
Add acid - The acid reacts with bicarbonates in the water and reduces the total alkalinity. Add 1.6 pounds of Dry Acid (Sodium Bisulfate) per 10,000 gallons of water, or 1.3 quarts of Muriatic Acid, to decrease the Total Alkalinity by 10 PPM. Retest and adjust the pH.
High levels of cyanuric acid will cause interference in the total alkalinity test. This interference is magnified at low levels of total alkalinity. To correct for cyanuric acid interference, measure the concentration of cyanuric acid, divide that number by 3, and then subtract that value from the measured total alkalinity value.
Minor deviations from the alkalinity levels stated in the CODE do not in themselves present imminent health threats to the BATHERS. As such, minor deviations in alkalinity levels do not require the immediate closure of the facility. Rather, deviations from permissible alkalinity levels indicate poor management of the water balance and should indicate a need for a thorough inspection of the entire facility.