The Expello Air Products Automatic Drain Valve eliminates moisture in compressed air systems. The valve replaces the manual drain petcock on any air tank within a vehicle's compressed air system, whether the tank is on a vehicle or trailer. The Expello valve purges water, dirt and oil from the air system in a quick, 1-second burst, every 5 minutes of vehicle on time. That means clean, dry air and an end to frozen air brakes. The 15 watt thermostatically controlled heater ensures year round air system protection.