Backwash filter with axial flow cartridge elements open at both ends during the filtration cycle and assembled concentrically. During the backwash cycle a powered mechanism presents one end of the cartridges singly, or in groups, to a dirt drain. Also claimed are cartridges with axial supports having a star-shaped cross-section with at least three edges over which a filter sleeve is fitted. Further claimed is the drive for the central shaft through a turbine driven reduction gear.
