The invention relates to a tap cock comprising a cock body (1) having a tap receptacle opening (2) and a cock gas passage opening (3) for the passage of gas to or from the tap receptacle opening, and a tap (4), the outer wall of which is rotatably supported in a gas-tight manner in the tap receptacle opening and comprises a tap gas passage opening (5) for the passage of gas from or to the cock gas passage opening through the tap, depending on an adjustable angle of rotation between the cock body and the tap. The outer wall of the tap comprises an open channel (6) connected to the tap gas passage opening (5) that can be at least partially covered by the cock gas passage opening (3), depending on the angle of rotation.