Abstract: An improved cartridge housing assembly and distributor is provided for a water filtration system installed at a point-of-use or a point-of entry of plumbing networks in buildings. The improvements include a mechanism for actuating a shut-off valve and a pressure-relief valve upon removing the housing assembly from the distributor, a bayonet-type mount between the housing assembly and the distributor, a housing lid to prevent spilling of water when the housing assembly is removed from the distributor, and fastener clips that allow for modular attachment of the distributor to plumbing fittings and a mounting bracket.