PURPOSE: To make a cartridge detachable by a finger-tip touch by providing a projecting structure on the water inflow orifice part of the cartridge and a recessed structure which is engaged with the projecting structure on a main system part, and installing a fixed ring which is detachable from a groove formed in the water inflow orifice, on the main system part.

CONSTITUTION: This tap-connected water purifier is composed of a main system part 1 and a cartridge 6 incorporating a filter medium. The main system part 1 is cylindrical with a tap fixing part 3 with an untreated water inflow orifice 2 provided on the top. In addition, fixed rings 5 with a formed button 4 are arranged at an opposite position to each other. In the cartridge 6, raw water passes through a water inflow part 6a and is purified by a cylindrical filter medium part consisting of activated carbon 6d and a hollow fiber membrane 6 to be discharged from a purified water discharge orifice 6f as a purified water. In this case, the water inflow part 6a is equipped with a projecting structure to be sealed by an O ring 6b and a groove 6c for the insertion of a fixed ring end. Thus it is possible to easily and rapidly detach the cartridge by a user in a finger-tip touch manner, as this water purifier is equipped with a joint mechanism.