Dirty water enters the inlet 1 and travels to the concave surface of the perforated screen 2. The water then passes through the screen and exits the outlet 3. Unwanted particles accumulate on the surface of the screen.

On activation of the rinse cycle, the rinse valve 4 is opened to drain. A portion of the water flows back through the screen, lifting the solids off. A portion of the flow also travels across the screen surface, carrying the solids to the drain.