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 deg F (1.7 deg C) and closes completely when the water climbs back to 42 deg F (5.6 deg C) or above. 1/2 in NPTF inlet and outlet.