A flow device having a body mounted in a sealing manner on a vessel, a spout arranged on an end opposite the vessel, a flow duct having a flow outlet situated on the spout and a flow inlet situated in the fitting portion, an air supply duct having an air inlet is situated on the body and an air outlet. The flow device also has a cap which is translationally moveable with respect to the body, the cap having a first valve and a second valve which cooperate respectively with a first valve seat formed by the flow outlet and a second valve seat which is separate from the first valve seat and is formed by the air inlet. A restoring element exerts a restoring force on the cap so as to keep the valves closed in the absence of an opposing force.