An integral water trap and venturi tube element for use in an exhaust stack on a vehicle, the exhaust stack being generally vertically oriented and having a catalyst element or other moisture-sensitive emission control component disposed below the water trap, the venturi tube having an aspirator tube disposed therein to provide a low pressure aspiration source for the vehicle, wherein the venturi tube is so disposed in the exhaust stack to also function as the water trap and allows capture and diversion of water entering the exhaust stack from above.