with a groove 80 in the side wall of the fluid inlet 20 the slots 78 provide an opening for the tabs 70 on the upper end cap 48 to be inserted into the lid 12 and turned into the groove 80 to provide a bayonet connection between the upper end cap 48 of the filter cartridge 14 and the lid 12 an o ring seal 82 is provided in a groove in the underside of the lid to seal against a sealing surface 84 on the upper surface of the end cap 48 the filter cartridge 14 is adapted for the influent to enter the filter cartridge through the openings 68 in the upper end cap 48 pass into the chamber 76 of the filter cartridge 14 formed between the bundle of hollow fiber membranes 52 and the interior of the side wall 46 of the casing 44 and then into the membranes and out through the opening 72 in the bottom end cap 50 in use the filter cartridge 14 is attached to the lid of the reservoir by inserting the tabs 70 into the slots 78 of the underside of the lid 12 and twisting the filter cartridge 14 to secure the bayonet connection with this arrangement the filter cartridge 14 is sealed against the lid 12 and the lid 12 may be secured to the pitcher 4 by the clamps 29 other types of.