Model SP158B, fully engineered freeze protection valve is constructed of a one piece brass body, and supplied with a removable cartridge for easy cleaning and maintenance. Automatic thermal actuator bleed valve opens when internal water temperature falls below 35 °F (1.7 °C) and closes completely when the water climbs back to 42 °F (5.6 °C) or above. 1/2 in NPTF inlet and outlet. Haws® Bleed Valve, 1-Piece Freeze Protected, Activates At: 35 °F, 1/2 in Inlet, 3-1/2 in Length, Brass