The present invention discloses an improved multiple filtration cartridge assembly comprising filter cartridges with internal riser tubes mounted on a collection rail via rail couplers. Within this configuration, at least one internal riser tube contains a drain down orifice which corresponds to a matching drain down orifice on the rail coupler. The disclosed assembly increases the lifespan of the filter cartridges. Further, the multiple filtration cartridge assembly may be configured as a filtration mechanism within a variety of Structural Best Practice Management water filtration systems.