Abstract: A device for filtering and sterilizing potable water for household use which may be connected in the water line at a faucet or ahead of the automatic ice-making mechanism of a refrigerator. The water is purified in two stages: The first stage uses an activated carbon filter to remove solid particles, dissolved gases and colloidal particles from the water; the second state uses intensive ultraviolet radiation provided by a mercury vapor lamp to kill essentially all bacteria, viruses and any other organisms which are not trapped by the activated carbon filter. The lamp is mounted concentrically within a cylindrical tube having a water inlet at one end and an outlet at the other end, so that the water is sterilized as it passes through the annular chamber defined by the lamp and the outer wall of the cylindrical tube. A solenoid-activated shut-off valve cuts off the water flow from the device whenever a control circuit detects a failure of the lamp or a loss of line power.