Designed to drain unusually heavy rains from flat roofs of any construction, this 16" (406) diam., Duco coated cast iron drain has a 11" (275) deep, 12" (305) diam. sump that allows entrapped air, which would stop water from entering the drain pipe/leader, to escape. Its combined gravel stop and flashing collar grips roofing membranes for a leakproof seal without puncturing. The drain is protected from debris by a low profile polyethylene dome.