Abstract: A drain valve including a housing engaged on a base, compressed air may flow into the housing via an inlet of the base, a casing disposed in the upper portion of the housing, a piston slidably engaged in the casing, a rod extended downward from the piston into an outlet of the base for blocking the outlet, a puncture formed in the upper portion of the casing, a plug disposed for blocking the aperture and can be opened by a float. The condensate is accumulated within the lower portion of the housing. Most of the parts are disposed within the upper portion of the housing.