Abstract: A method and apparatus for delivering disinfectant in a liquid form to a well of a water system is disclosed including a venturi having a suction side in fluid communication with a source of disinfectant such as chlorine. A flow of water is provided through the venturi between the pressurized side of the water system and the well when a pump is drawing water from the well and delivering the water to the pressurized side of the water system. Specifically, a solenoid valve is provided in the lines between the pressurized side of the water system and the venturi and is electrically controlled by the pressure switch which also controls the pump. In the preferred form, a timer is provided electrically intermediate the solenoid valve and the pressure switch to allow water flow through the solenoid valve only during selected times of pump actuation to allow adjustment of the rate at which the disinfectant is delivered.