Why is hard water a problem for swimming pool water and what are the proper concentrations?
Hard water is the most predominant problem with swimming pools in Arizona, and many other regions of the country. This is due to the presence of Calcium, Magnesium and other minerals present in the potable water used to fill and maintain appropriate water levels in pools and spas. Hardness is measured in parts-per-million (ppm.) or in milligrams per liter, both representing the same number. A typical hardness in Phoenix tap water has been seen as high as 1000ppm. The ideal concentration for a swimming pool is approximately 150-300ppm. Concentrations above 300ppm are much more problematical for the pool owner, making the pool water hard to control with respect to clarity and chemical stability. Although low concentrations of hardness are virtually impossible to achieve here in the southwest, high concentrations are almost commonplace.
