Abstract: A drain cover assembly 10 for venting a drain 14 located below grade to the ground level is disclosed. The assembly includes a hollow frustro-conical drain cover 12 which opens downward to cover the top of a floor drain 14. The lower annular end surface 64 of the drain cover 12 is provided with a rubber seal to engage the top of the drain 14. The drain cover is held in place by a jack screw which extends between a recess 46 in the top of the drain cover and the structure above, typically the ceiling of a basement. A flexible conduit is connected with the drain cover and extends upward through a window 20 or other opening to the ground level. When water from a sewer system backs up through the drain 14, hydrostatic pressure forces the water through the flexible conduit 18 to a location remote from the building in which the drain is located.