Abstract: A water treatment device which is of simple construction and operation, and which can provide sufficient oxidant gas to disinfect drinking water for about 3,000 people. The device includes an electrolysis unit, a water flow circuit with constant water flow and a venturi which aspirates the oxidant gas produced by the electrolysis unit. A timer turns the electrolysis unit on and off to maintain oxidant gas levels substantial constant in the water supply and a valve is provided which is operated by a timer unit to replace water in the anode compartment of the electrolysis unit. When the electrolysis unit is shut-off for maintenance, the venturi is used to aspirate liquid from the electrolysis unit, thus avoiding operator contact with caustic chemicals to the extent possible.