There is disclosed an apparatus for cleaning circular filter screens comprising at least one suction chamber fitted to a conduit of the dirt collection conduit system extending along a central axis of the housing of the filter screen. The suction chamber comprises a central nozzle through which fluid is forced to flow by virtue of a pressure differential between the outer surface of the filter screen and an extremity of the dirt collection conduit system. The fluid flow through the central nozzle creates a low pressure regime near the mouth of the central nozzle such that fluid is forced through a plurality of peripheral suction nozzles arranged around the central nozzle from the outer surface of the filter screen to the inside of the suction chamber, thereby forcing the dirt and retentate accumulated along the inner surface of the filter screen to be washed away.