Water from the system is pumped through the over-drain assembly at the top of the filter tank and distributed evenly over the media. Unfiltered water flows downward through the filter media where suspended particles are trapped. The filtered water then passes through the vessel and out the under-drain assembly at the bottom of the filter and returns to the system. Precision slots cut in the under-drain prevent the passage of media to the outlet. When the trapped particles cause the pressure differential across the media bed to reach a pre-determined pressure (approximately 16 psi), flow is reversed through the tank by repositioning the valves. The media is backwashed with a rigorous scouring action, releasing trapped particles within the media. The dirty water passes from the filter vessel through the over-drain assembly at the top of the vessel and flows to drain. After the backwash cycle, the filter valves are again repositioned and the filtration cycle is resumed. The filter uses system water for backwash. The mechanical nature of the system guarantees an immediate improvement in water quality.