Abstract: An adapter for connection to a liquid faucet comprises an inlet member, a coaxial outlet member, and a valve device which is rotatable relative to the outlet member about an axis common to the inlet and outlet members. The inlet member is connectable to the outlet end of the liquid faucet. The outlet member has several outlet openings or groups of outlet openings separated from each other. The valve device is rotated in order to continuously adjust the opening ratio between the various outlet openings of the outlet member relative to each other, thereby providing a precisely regulated amount of liquid which is branched off from the liquid faucet for operating auxiliary devices such as a douche.