A water purification system for purifying water from a conventional supply of tap water and dispensing a predetermined quantity of processed water into a user-supplied container in response to the deposit of a predetermined value of specie, coin, or token. The system includes a first purified water path and a second drinking water path. The first purified water path includes a reverse osmosis filter, a tank, and an afterfilter coupled between a prefilter and an ultraviolet disinfecting apparatus. The second path is substantially in parallel with the first path and includes a polishing filter. Manually operated switches can be used to select either drinking water of purified water and timing means are provided to insure that a predetermined quantity of water is supplied from the dispensing means into the user-supplied container. Valves are used to operate the first path for purified water, and the second path for a limited time followed by the first path for a longer time for better tasting drinking water. The system also includes a detector for sensing improperly processed water from the reverse osmosis filter and a diverter for sending improperly processed water to a sump. The ultraviolet disinfecting system or apparatus includes a hollow plastic housing with a lamp mounted therein. The lamp is wrapped in plastic and an annular space between the outer surface of the lamp and the inner surface of the housing provides a flow path for the purified water during which time disinfecting takes place prior to dispensing.