A self-purging filtering apparatus having a pressure vessel connected for discharging clean filtrate to subatmospheric pressure at a pump inlet. Actuators connected to an outwardly extending rod move a wiper piston to scrub the upstream side of an annular filter media element. The piston moves a main valve member to isolate a purge chamber from the filtering chamber. Remotely operated valves control flushing of the purged chamber. The main valve has a bleed valve to provide pressure equalization for facilitating main valve movement.