A device that permits the in-home UV treatment of drinking water such as tap water is disclosed. The device employs a bare low-energy UV lamp suspended below a reflector and above a free surface of water flowing within the device. The water is supplied from a tap or other store of drinking water and proceeds through the device by the force of gravity. The device itself is not pressurized. The flow of water within the device is exposed to UV radiation from the UV lamp and is disinfected as a result. In the illustrated embodiment, the device is of a small size to permit its use, for example, directly at a tap for drinking water within the home. The flow rate of the device is commensurate with the normal flow rate of tap water, preferably less than about 8 liters per minute. The lamp power for safely disinfecting the water can be less than 20 watts, and in the illustrated embodiment the lamp is a low-pressure Hg lamp.