Automatically Drain Moisture & Water from your Truck/Trailer Air Brake System Tanks by using #EXT-50-12V Electronic Drain Valve. Once Connected to the Air Tank and Ignition Power Circuit the #EXT-50-12V Drain Valve Will Operate Every 6 Minutes. This Product Can Be Used in Conjunction with #XD-30 to Drain Two Tanks Simultaneously. Outer Body is made from Air Craft Quality Aluminium. Recommended Service Period Twice Yearly for Transport Trucks and Recommended Service for Waste Compactor Trucks Every Three Months.