A water disinfection apparatus includes a chamber adapted for connection to a pressurized water source. An ultra violet light is oriented to shine ultra violet rays into the chamber and to disinfect water therein, and a normally closed output valve connects the chamber to a supply valve. A control senses when a connected supply valve has been opened, and is operative to turn the ultra violet light on when the connected supply valve is opened; open the output valve after the ultra violet light has been turned on; close the output valve off after a supply time period expires; and turn the ultra violet light off when the output valve has been closed. The ultra violet light is turned on at all times that the output valve is open.