F2000 Media Filters (gravel or sand) are the most efficient type of filtration of water heavily contaminated with algae, organic matter and other impurities found in open reservoirs, canals and recycled water systems. The filtration occurs when the water passes through the open spaces and between sand particles, trapping the solid particles. The F2000 Media Filters use a bed of sand approximately forty centimeters deep to filter particles out of the water. The dirt particles are trapped in the open areas between the sand particles are removed during the backwash cycle. This dirt and backwash water is expelled out of the tank and into a disposal area.