a fluid filter assembly incorporates a filter element and valve assembly within a filter housing and base plate . the filter element and valve assembly is a single pre - assembled unit which includes an anti - drainback valve seat and diaphragm , a by - pass valve assembly , a pleated paper filter element , and a spring endcap . the filter housing and base plate separably clamp together to enclose the filter element / valve cartridge which is replaceable , as a single assembly , once its filtering ability is degraded . the anti - drainback valve seat engages complementary features on the base plate to correctly align and position the filter / valve cartridge during assembly . further , a recess within the top of the filter housing receives a protrusion on the filter element endcap to provide additional alignment and to provide pressure to seal the filter / valve cartridge to the base plate in a fluid - tight manner .