Abstract: A pressure switch adaptor designed to replace existing pressure switch adapters or connections and pressurizing air valves conventionally associated with water storage and distribution tanks. The adaptor is designed to be used as original equipment on new water tanks or to retrofit existing tanks, replacing the pressurizing air valve conventionally provided by the latter. Whether used on a new tank or retrofitting a used tank, the pressure switch adaptor fits into the port conventionally reserved for the pressurizing air valve. The adaptor provides a pressurizing air valve to allow initial pressurization of the air filled diaphragm and a pressure switch connection for fluid communication between an internal tank diaphragm and the pressure switch, which controls actuation of the tank's water-supplying pump. By placing the pressure switch adaptor on the air side of the system, problems associated with corrosion and corruption of the switch due to prolonged contact with water are eliminated.