The water then filters slowly through the medium until it reaches the bottom of the tank where it is collected through a specially-designed sieved “basket” at the bottom of the center tube seen in the picture.
The unfiltered water enters from the left and is routed by the control valve into the filter tank. This is how it works when it is doing the job it is designed to do. The picture at right shows the filter in “service” position. Many media are known by their brand names of the leading product in the category: Centaur, Filox, Birm, Filter Ag, and KDF, for example. Common media are granular carbon, sand, garnet, anthracite, zeolite, granular manganese dioxide, and greensand. Media (media is plural, medium is singular) are numerous and varied. The filter bed itself is a granular substance that is usually referred to as the filter medium. Backwashing consists of reversing the flow of water so that it enters from the bottom of the filter bed, lifts and rinses the bed, then exits through the top of the filter tank. Backwashing water filters are large tank-style filters that get their name from the fact that they clean and renew themselves by backwashing.
