What’s That Stuff? Pool chemicals

Abstract

People love to complain about chlorine in pools—often as much as they enjoy plunging into the clean water. Chlorine-based compounds can dry out skin, turn eyes red, and produce the familiar and pungent pool smell. On the other hand, thanks to chlorine, we can swim in water free of microbes, such as Escherichia coli, that can cause digestive troubles. In addition to disinfectants such as chlorine, pool operators also add chemicals to control the pH, alkalinity, and hardness of the water. The chlorine used to disinfect pools is rarely present as elemental chlorine (Cl2). It’s typically added as part of more complex molecules such as hydrogen- and oxygen-containing hypochlorites or carbon-, nitrogen-, and oxygen-containing isocyanurates, explains Thomas M. Lachocki, chief executive officer of the National Swimming Pool Foundation. When these compounds are added to water, they spontaneously form hypochlorous acid, which is the disinfecting agent commonly called free chlorine in