Patent attributes
A stormwater filter cartridge includes a housing with internal filter medium disposed along a flow path between a water inlet and a filtered water outlet. A solid wall float tube in a drainage space has an open lower end and open upper end and is movable between a lowered position and a raised position. As the housing fills, water level in the housing rises to cause the solid wall float tube to move to the raised position and a negative pressure draws fluid through the filter medium. As water level outside the filter cartridge drops, air enters the housing and causes the solid wall float tube to drop to the lowered position, and filtered water in a fluid reservoir backflows through the filter medium while air enters the housing by passing upward through the solid wall float tube so as to enhance rate of backflow.