A tide gate 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 and a downstream fluid outlet region, wherein the upstream fluid inlet end region and/or the downstream fluid outlet region is adapted to be affixed to a conduit; (b) the downstream fluid outlet region of said sleeve being integrally formed with a longitudinally-extending trough, said trough having a bottom wall and a pair of side walls (24, 26) integral with said bottom wall, said trough formed with said downstream fluid outlet region of said sleeve so as to provide a flow-through passage for said fluids; (c) a disc comprising a first material affixed along a first portion of its periphery to a flexible hinge member, said flexible hinge member affixed to and interposed between said disc and said downstream fluid outlet region of said sleeve, said flexible hinge member comprising a second material which is more flexible than the first material of said disc, and wherein a second portion of the periphery of said disc opposite said first portion rests within said trough on said bottom wall of said trough when said valve is in a closed position, wherein said disc opens said valve in response to positive differential pressure within said valve; (d) a bill affixed at a first end to one or more of the group consisting of the sleeve, the flexible hinge member, and the disc, said bill extending longitudinally downstream along said longitudinal axis of said trough, said bill being integrally formed with said side walls (24, 26) of said trough, said bill being formed of a flexible material and forming an opening for discharge of fluid in response to a 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; characterized in that the tide gate check valve further comprises: (i) at least one groove in a surface of the disc, wherein the at least one groove extends longitudinally along a length of the disc; and (ii) at least one notch that extends laterally along a width of the bill. (a) a tubular sleeve bounding a longitudinally-extending flow-through passage for fluids, said sleeve having an upstream fluid inlet end region and a downstream fluid outlet region, wherein the upstream fluid inlet end region and/or the downstream fluid outlet region is adapted to be affixed to a conduit; (b) the downstream fluid outlet region of said sleeve being integrally formed with a longitudinally-extending trough, said trough having a bottom wall and a pair of side walls (24, 26) integral with said bottom wall, said trough formed with said downstream fluid outlet region of said sleeve so as to provide a flow-through passage for said fluids; (c) a disc comprising a first material affixed along a first portion of its periphery to a flexible hinge member, said flexible hinge member affixed to and interposed between said disc and said downstream fluid outlet region of said sleeve, said flexible hinge member comprising a second material which is more flexible than the first material of said disc, and wherein a second portion of the periphery of said disc opposite said first portion rests within said trough on said bottom wall of said trough when said valve is in a closed position, wherein said disc opens said valve in response to positive differential pressure within said valve; (d) a bill affixed at a first end to one or more of the group consisting of the sleeve, the flexible hinge member, and the disc, said bill extending longitudinally downstream along said longitudinal axis of said trough, said bill being integrally formed with said side walls (24, 26) of said trough, said bill being formed of a flexible material and forming an opening for discharge of fluid in response to a 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; (i) at least one groove in a surface of the disc, wherein the at least one groove extends longitudinally along a length of the disc; and (ii) at least one notch that extends laterally along a width of the bill.