Abstract: The invention relates to a valve unit (26) comprising a cartridge and valve holder (1), which has means (6) for connecting the same to a cartridge protective housing (3), means (7; 36, 49) for sealingly fastening the same in a hole (10) that is provided for this purpose in a liquid receptacle (11) as well as a lateral, continuous hole (20), an internal housing (4), which is mounted in the cartridge and valve holder (1), in which a tapping tip (8) and a pressure-reducing valve unit (13, 14, 15, 16, 17, 18) are located at the end of the internal housing (4) facing the cartridge protective housing (3), wherein the pressure-reducing valve unit has a pressure-regulating chamber (13), wherein the pressure-regulating chamber (13) encompasses a connection to the interior of the liquid receptacle (11) via a continuous hole (19) in the internal housing (4) and the lateral, continuous hole (20) in the cartridge and valve holder (1), which [connection] is protected or can be blocked by a non-return valve.