In the treatment of water, an end piece is connected to a treatment cartridge housing and inserted into an appliance having bypass, inlet, and outlet valves. The end piece has an end piece wall from which an inlet fitting, outlet fitting, and protrusion extend. The inlet fittings, outlet fittings, protrusion, and cartridge housing each have a longitudinal axis. The inlet and outlet fittings have a cam surface for actuating the inlet and outlet valves, respectively. Further, the cam surfaces of the inlet and outlet fittings are angled and vectored in relation to their respective longitudinal axis. The protrusion is shaped for actuating the bypass valve.