The backwash process cleans the filter by reversing the water flow. Clean water from the rest of the system is directed into the filter’s outlet, while simultaneously, the inlet valve closes and the drain valve opens. The upward flow of water expands the sand bed, releasing trapped particles, which are then flushed out through the drain line. This procedure can be performed manually or set to occur automatically. An automatic system requires a minimum of two filters to ensure a continuous supply of clean water for the backwash cycle.

Sand filters work by passing contaminated water downward through a multi-layered bed of sand. As the water travels through the fine spaces within the sand media, physical and organic particles are captured and removed. At the bottom of the tank, a network of diffusers or mushrooms collects the purified water and sends it to the outlet, while securely holding the sand media in place. The type and layering of the sand can be specifically selected to match the water quality and achieve the desired filtration level.