Odor trap for drain

Claim 1

An odor trap for a drain, comprising: an upwardly open housing having a substantially flat sidewall provided with an exit port for entering waste water; a tubular insert in said housing adjacent said sidewall, said insert having a peripheral wall forming a bottom inlet beneath the level of said exit port and a circular lateral outlet registering with said exit port; mounting means securing said insert to said sidewall; and an upwardly concave tongue in said insert spaced from said peripheral wall and extending inwardly from the lower periphery of said outlet, said tongue having a curved bottom hugging said outlet over substantially the lower third of its periphery and a pair of upstanding flanks on opposite sides of said curved bottom, said flanks rising to a level below a horizontal midplane of said outlet, said curved bottom rising to the same level and merging there gradually into said flanks along a generally U-shaped overflow edge whose bight is curved about a vertical axis disposed inwardly of said outlet and whose arms defined by said flanks are substantially perpendicular to said sidewall, said overflow edge being separated by a generally ring-segmental clearance from said peripheral wall, said clearance terminating at said sidewall and having a horizontal cross-sectional area at least equaling the cross-sectional area of the flow path of said outlet.