Filter system for a liquid stream with automatic rapid back flush

Abstract

A system for filtering a liquid stream, typically drinking water from a natural source. The system includes a plurality of filter stations, each of which receives at least a portion of the influent liquid flow, passes the flow through a filter and passes the filtered liquid to an affluent line. When the filter has reached its capacity for removing particulate material from the liquid flow, preferably as determined by measurements of pressure drop across the filter media, a small quantity of the clean affluent liquid is passed through the filter in a reverse direction to back flush the filter media, with the flush liquid directed to a waste water line. Back flushing can be accomplished automatically under microprocessor control, using signals from a filter media pressure sensor. With a plurality of parallel filter arrangements, continuous flow to the affluent line is easily maintained, since the back flush cycle is short and all filter sets would not be in the back flush mode at the same time. The filter has a porous tubular core bearing filter media on the core surface. The core is housed in a canister having an entrance directing influent liquid into the canister tangential to the core and an affluent line connected to the interior of the core. This configuration provides improved filter media life and efficient reverse flow during back flushing.