The automatic drain valve is used to discharge liquid contaminants from air receiver and / or centrifugal air filter with coalescer through dual exhaust ports in the locomotive. It is a double seated valve and very rugged in construction. The valve is actuated pneumatically by either the compressor unloader solenoid valve or other pneumatic source on a cycle or regular basis, i.e. Air Dryer actuating source or a locomotive microprocessor with an independent solenoid valve. The valve is also designed with an integral drain/shut-off feature to manually exhaust contaminants as desired. Automatic Drain Valve is supplied with a flange-type mounting bracket for ease of installation on standard locomotive air reservoirs or flange sump caps commonly used with the Centrifugal Air Filter with Coalescer. A thermostatically controlled heater assembly is available for severe weather applications.