rotatability of member 20 provides selectable communication of slot 22 with the outer surfaces of each of elements 18 while the rotatability of each of elements 18 permit the slot 22 when in engagement with a given element 18 to effectively scan the entire outer surface of the element as it is rotated in the illustrated embodiment of the invention a water inlet 24 for water to be filtered is provided at the side of the housing such that water to be filtered is provided at the outer surface of each of the filter elements 18 the interior surfaces of each of the elements communicate via a suitable manifold 26 which does not impede rotation of the elements about their longitudinal axes with a filtered water outlet 28 the engagement member 20 communicates via a manually or otherwise operable valve 30 with the outside atmosphere or any relatively low pressure receptacle it is seen in fig1 and 3 that each of the elements 18 is provided with a suitably splined extension 32 which passes through the housing 10 via a suitable sealing bushing 34 or the like and which permits rotation of the element 18 about its longitudinal axis from outside the housing 10 the engagement member 20 is provided with a similar extension 35 for rotation of engagement member 20 about its own axis a rotation crank handle 36 having an associated socket 38 arranged for removable engagement with extensions 32 is rotatably mounted on a handle support 39 handle support 39 is in turn mounted for rotation together with extension 35 such that the location of the socket 38 is coordinated with the orientation of the slot 22 of the communication member 20 whereby when socket 38 engages the extension 32 of a.