A variably tensionable check valve with a first end and a second end that includes a housing, a tension adjuster, a resiliently deformable elastic member, and a flow restriction member biased in a closed position. The housing includes a first portion, a second portion, and first and second passageways with a transition portion therebetween. The second portion includes at least one peripherally extending raised rib and a second internal passageway. The surface area of a cross-section of the first internal passageway is greater than the surface area of a cross-section of the second internal passageway. The tension adjuster, the elastic member, and the flow restriction member are located within the first internal passageway, wherein the tension adjuster secures the elastic member and the flow restriction member within the first internal passageway, and wherein rotational movement of the tension adjuster modifies the biasing force of the elastic member.