Abstract: A coupling serving for connecting a double valve on a pressure container with a content of pressure gas, such as CO2, and a liquid, such as beer, to a pressure-gas source and a tap for drawing the liquid respectively. The valve comprises a blockable gas and liquid passage respectively, and the coupling comprises a housing for coaxial mounting on an upper flange on the valve, a slide which is placed in the housing and which can be displaced by means of a hand grip between an upper position where the valve is closed and a lower position where the valve is open; an elastomeric sleeve secured onto the slide and forming sealing between the slide and the valve flange in the mounted position of the coupling; a mainly tubular plunger secured in the slide; and a gas chamber formed between the plunger, the sleeve, and an inner wall in the slide.