Abstract: An odor trap apparatus (20) includes a housing (32) having an interior and an opening (48) extending from the interior to the external drain, and a cartridge (22). The cartridge has an exit opening (78) disposed to communicate with the housing opening. The cartridge and the housing have positions of final secured interconnection, when openings (26, 48) are aligned, and of initial unsecured interconnection, when their openings are not aligned. A lever (52) is swivelably secured to the housing bottom wall (46), and has a cap (54) for closing the housing exit tube (28) and a projection (56) engageable with the cartridge for effecting the closure when the housing opening (48) is not aligned with the cartridge exit opening (78). Three L-shaped keyways (60) in the housing interior are adapted to mate with three keyways (82) in the cartridge, and have corrugated surfaces to provide a ratcheted secure connection between the cartridge and the housing when in the secure orientation.