Abstract: A filter belt is progressed stepwise over successive vacuum boxes by a guide roller at the forward end of the upper run being extended from its retracted position to its full line position while vacuum to the boxes is shut off. A displaceable roller permits this by taking up any slack in the belt and return movement of the belt upon retraction of the foremost guide roller is prevented by a unidirectional arrangement in at least one of the rollers guiding the lower return run of the belt. Slurry is fed onto the belt by a first nozzle, optional wash liquor is fed onto the resultant filter cake by a second nozzle and optional recirculated wash liquor is fed by a third nozzle all under the influence of a control which provides for such feed only for a predetermined period of time during the actual movement of the belt.