Abstract: A valve (10) for a water temperature control system having a heat exchanger (C), a tank (T), and a pump (P) for circulating heat transfer fluid through a supply line (11, 12, 13) from the tank to the heat exchanger and through a return line (14, 15) from the heat exchanger to the tank including a valve housing (20) interposed in both the supply line and the return line having supply inlet and supply outlet connections (24, 25), having return inlet and return outlet connections (26, 28), and having first and second drain connections (29), a valve element (45) associated with the valve housing having a first position for normally circulating the heat transfer fluid from the supply inlet connection to the supply outlet connection and from the return inlet connection to the return outlet connection and having a second position discontinuing circulation through the supply inlet connection and the return outlet connection and connecting the supply outlet connection to the first drain connection and the return outle