An improved floor drain valve for buildings, basements, exterior paved areas, and the like. The invention provides floor drain assemblies and check valves providing improved drainage performance, particularly where drainage is an irregular occurrence, and having unprecedented simplicity and reliability. Floor drains according to the invention comprise check valves having elastomeric hinge structures mounting relatively rigid flapper structures biased upwardly against sealing surfaces adapted for disposition within floor drains. Water entering the valve structure opens the flapper valves by gravitational forces downwardly against the relatively rigid flapper, and after passage of the water, the valve is elastomerically urged into the sealed position restricting back flow of gases from the downstream area of the drain conduit and permitting pressure testing of the downstream conduit.