Abstract: Disclosed is an improved tank vent. The vent prevents liquid loss if the tank is inverted and prevents contaminants from entering the tank. The vent includes an elongated housing forming a tubular chamber communicating with the interior of the tank. Disposed within the chamber is an annular valve seat. Disposed within the chamber adjacent the valve seat is a free sliding elongated buoyant valve member. The buoyant valve member has a protruding valve surface disposed on the end of the buoyant member adjacent the valve seat. The surface area of the valve surface is significantly less than the surface area of the end of the buoyant member upon which the valve surface is disposed. The valve surface is configured to sealably engage the valve seat for movement into and out of contact with the seat as the buoyant member moves within the chamber.