A ball cock has a housing that includes at least two housing parts. Each part has a flow-through channel as a flow-through path. The ball cock also includes a ball-shaped shut-off element having a passage bore as a flow path for optionally connecting the flow-through paths of the housing parts. This shut-off element is accommodated within the housing between ring-shaped seals, and can be switched by means of a switching shaft between an open position in which the flow path is released and a closed position that shuts off the flow path. At least one of the seals that accommodate the shut-off element between them is mounted in one of the housing parts, with limited axial mobility, and can be pressed against the shut-off element with a sealing surface by means of a device, whereby the seal can be switched between an axial contact pressure position and a stress-relief position.
