Abstract: A housing adapted to receive a flow of slurry has a central section, an upper section, and a lower section. A clean water introduction assembly has a horizontal manifold, a plurality of horizontal apertured pipes and a plurality of vertical water lines. A valve assembly has an upper valve and a lower valve. The upper valve is normally open. The lower valve is normally closed to feed clean water from the manifold through the water lines and out of the apertured pipes into the housing. In this manner water entering the housing will cause a hindered settling. The valve assembly is also operable in a back flow mode with the upper valve being closed and the lower valve being opened. In this manner water from the housing will flow from the apertured pipes. In this manner clogs in the holes of the apertured pipe are cleared. A coupling assembly is provided.