A method and apparatus for sanitizing a water dispenser that dispenses water for human consumption is disclosed. The dispenser can be in the form of any dispenser that dispenses water for human consumption employing a reservoir that dispenses water through one or more spigots. Water in the reservoir is sanitized with an air/ozone gas mixture that is transmitted to a porous polymeric diffuser having a central bore and a porous wall. The porosity of the porous wall defines bubble size.