Abstract: A drain valve includes a valve body, inlet and outlet ports, a first bore communicating between the inlet and outlet ports and a second bore intersecting the first bore at a right angle. A slidable member is mounted for reciprocal movement within the second bore. The slidable member includes a pin comprised of a resilient composite material, such as virgin tetrafluoroethylene, which maintains its resiliency throughout a wide range of temperatures and pressures. The diameter of the pin is slightly greater than the diameter of the second bore. As such, the pin is compressible to allow the pin to be inserted into the second bore and is expandable against inner surfaces of the valve body defining the first and second bores to provide a positive seal along substantially the entire length of the pin. An effective seal is maintained, despite variations in temperatures and pressures, to prevent leakage and accidental movement of the slidable member. A slot is cut in the pin to function as a guide slot.