by PHTA Recreational Water Quality Committee July 2021
Total alkalinity in pool or spa water provides buffering so that pH does not swing in and out of the proper range in response to sanitizer addition, bather load or other factors. With total alkalinity levels too low, there will not be enough buffering, and the pH may quickly drift out of the proper range.
Maintaining total alkalinity depends on keeping the concentration of CaCO3 (calcium carbonate) within the recommended range, thus reducing the tendency of pool and spa water to scale or etch surfaces. The ANSI/APSP/ICC11 2019 American National Standard for Water Quality in Public Pools and Spas by the Pool & Hot Tub Alliance states that total alkalinity shall be maintained between a minimum of 60 ppm and a maximum of 180 ppm as CaCO3.