US Patent 7739757 Shower base with flow enhancing covered drain

A shower enclosure base has a flow enhancing flush-mounted drain cover that conceals the drain opening and provides a flat stepping surface. Drain flow is achieved through a narrow peripheral passage between the drain cover and the drain well in which it is seated. Despite the reduced flow area of passage, flow enhancing features of the drain cover serve to improve the flow rate through the drain. These features are radially converging ribs at the underside of the drain cover that interrupt the natural tendency for drain water to form a vortex as it passes into and through a circular drain opening. The drain cover can be removably secured to the base by suction cups that attach to the drain well.