Two important compounds determine waters alkalinity: carbonate (CO32) and bicarbonate (HCO3-). In pool water, bicarbonate should be between 80 and 120 parts per million for an idea range. When the total alkalinity (TA) is within this range, the water is buffered against sudden pH changes.
When TA is too low, the water may turn green and swimmers eyes may burn. In addition, the walls of the pool can be etched and stain. When TA is too high, the water becomes cloudy and chlorine loses its disinfectant properties.
TA should be checked regularly. To raise TA, add bicarbonate, such as sodium bicarbonate. An online calculator can calculate the proper amounts. To lower TA, add a liquid or dry acid to the deepest part of the pool, being sure that the filter is turned off. Again, an online calculator can establish the correct amount of acid to be added. Changing a pools alkalinity can be a lengthy, back-and-forth process.