The present invention provides valve assembly for use in a floor drain. In various embodiments, the valve assembly comprises a substantially cylindrical seal frame, the seal frame defining a seal frame wall and at least one support wall extending in the longitudinal direction of the seal frame, a flexible sealing member located proximate a distal end of the seal frame, and an attachment tab configured to secure the flexible sealing member to the seal frame, wherein the seal frame and the support wall are further configured to create a resting deflection of the flexible sealing member, such that fluid may flow through the valve assembly in one direction, and the flow of gasses through the valve assembly is prevented in the opposite direction.