The Freeze Miser operates like the thermostat in your home. After installation, it senses the internal water temperature arriving at the faucet, not the air temperature. The Freeze Miser activates when the water temperature drops below 37? F/3? C. No water is released until the activation temperature is sensed. The Freeze Miser is on guard 24/7! Faucet protection in just 2 SIMPLE STEPS: Hand-tighten the Freeze Miser on your exterior faucet. Open faucet all the way to ensure that water pressure is available to the Freeze Miser (Minimum 10 PSI). And that?s it ? YOUR FAUCET IS PROTECTED FROM FREEZING!