A valve comprising an inlet housing, an outlet housing, an elastomeric valve element having a generally dome-shaped configuration with a central integral stem positioned substantially concentrically therewith, the inlet housing and outlet housing being fastened together at a joint with the elastomeric valve element positioned therein and the valve element including a plurality of longitudinal ribs formed along an outer annular periphery of a lower end of the dome-shaped configuration that define flow channels that allow fluid flow from across an upper surface of the dome-shaped configuration through the flow channels.