As a result, home systems commonly use a series of cartridge filters, with each filter removing smaller particles. Another option is a rapid sand filter followed by two cartridge filters. These systems filter all the water entering a home. Some people treat only the kitchen tap water for drinking. An option in this case is to use reverse osmosis followed by ultraviolet light or a small distillation unit.
Disinfection is needed because some bacteria and viruses can pass through filters.
When disinfecting using constant chlorination, a small pump automatically injects a diluted chlorine solution, usually household bleach mixed with water, into the water pipe below the filter. The chlorinated water then flows into a holding tank, where the chlorine kills any organisms. This disinfects the entire home plumbing system. Constant chlorination systems require some maintenance by the owner. The amount of chlorine needed to kill harmful organisms depends on the temperature and acidity of the water and the length of time the organisms are in contact with the chlorine.