Abstract: A backflush attachment for a filtering device, in particular for a plastics melt filter, the backflush attachment comprising a housing having guide channels following an entry bore, as well as backflushing channels, and at least one rotary piston which enables a flow passage in the respective guide channel when in its passing position and which interrupts the passage in the guide channel from the entry bore to the filtering device when in its closing position while providing a connection of a portion of the respective guide channel with an associated backflushing channel leading outside of said housing, the rotary piston having an eccentrically arranged passage channel of constant cross-section substantially corresponding to the cross-section of the guide channel, the axis of rotation of the rotary piston extending eccentrical in corresponding manner relative to the axis of the guide channel, and the passage channel forming a part of the guide channel when the rotary piston is in its passing position, whereas