Chlorine It is used to kill nasty bacteria. When you use a hot tub, the warm water picks up oils, fats, dirt and hair from the surface of your skin. Bacteria from the air and unclean water can feed on deposits left in the hot tub, if there are enough bacteria it can lead to the development of infectious diseases. Therefore, it is essential to use chlorine to control bacteria levels. You must always use the STABILISED versions of these chemicals i.e. commercially available for