Alkalinity P and Alkalinity M (Total Alkalinity) are important tests in boiler water treatment control where the pH of water is over 8.5. Results are usually reported in mg/l as Calcium Carbonate (CaCO3).
Alkalinity P is the alkalinity of the water to pH 8.3, uses a phenolphalein based indicator and represents the alkalinity due to hydroxides plus half the alkalinity due to carbonates.
Alkalinity M is a measure of the alkalinity of water to pH 4.5 and uses a methyl orange based indicator. Results represent the total alkalinity due to the combined concentration of bicarbonates, carbonates and hydroxides. Total Alkalinity is also an important test in swimming pools as it plays a part in maintaining the water balance.