How does a vacuum sand filter work?
Most sand filters function by mechanically straining solid impurities from the water. Water from the pool is forced into a pressure vessel, where filtration takes place at the top of the media bed by simple entrapment of particles. This results in shorter filter runs and frequent backwashes as the upper portion of the bed becomes clogged. By contrast, with vacuum sand filtration, water is drawn through the media, where electrostatic attraction between sand grains and the contaminant particles occurs. This process, called depth filtration, utilizes the entire media bed and results in the removal of extremely small particles. Under the vacuum, even tinier colloidal particles group together to form larger particles which can be removed, resulting in the clearest, cleanest water possible. Depth filtration means long filter runs—often four to six weeks, for which the Paddock Compak filters are famous—as opposed to pressure filters which often require daily backwashing, consuming significant
