Check Valve With Secondary Flap

A check valve comprising:

• (a) a tubular sleeve bounding a longitudinally-extending flow-through passage for fluids, said sleeve having an upstream fluid inlet end region adapted to be affixed to an effluent conduit and a downstream fluid outlet region;
• (b) the downstream fluid outlet region of said sleeve being integrally formed with a top wall, a pair of side walls, and a bill, said downstream fluid outlet region of said sleeve providing a flow-through passage for said fluids;
• (c) a disc affixed along a first portion of its periphery to a flexible member, said flexible member affixed to and interposed between said disc and at least one of said top wall and said pair of side walls of said sleeve, wherein a second portion of the periphery of said disc opposite said first portion is affixed to said bill of said sleeve, and wherein said disc opens said valve in response to a first positive differential pressure within said valve;
• (d) the bill being integrally formed with said side walls of said sleeve, said bill being formed of a flexible material, said bill forming a first opening for discharge of fluid in response to the first positive differential pressure within said valve from said fluid, and said bill forming a seal to prevent backflow of said fluid through said valve when no differential pressure or negative differential pressure is present;
• and
• (e) a flap affixed to said disc via a flexible hinge, said disc defining an aperture forming a second opening for discharge of fluid in response to a second positive differential pressure within said valve from said fluid, wherein said second positive differential pressure is less than said first positive differential pressure, and wherein said flap forms a seal against said aperture to prevent backflow of said fluid through said valve when no differential pressure or negative differential pressure is present.