The Zurn Wilkins ZWFR Backflow Preventer Freeze Protection Device monitors the water temperature within the valve. When the temperature-regulating thermostat senses that water is nearing the freezing point (35° F/1.6° C), the valve opens, allowing warmer supply water to flow into the system. As the system reaches 40° F/4.4° C, the valve closes. It threads into any standard 1/4” test cock. The compact design makes it easy to install on new and existing installations on virtually any brand of backflow preventer without the need to shut down or drain the system. It also can be used to protect other mechanical equipment, including any smaller-diameter commercial or residential outdoor plumbing system to prevent pipe, pressure-reducing valves, shutoff valves or fixtures from freezing.