B. Check that check valve is slightly unseated.
(1) Lay flange on a straight edge.
(2) Allow edge of the swing check valve opposite hinge to be flush with straightedge.
(3) Check that a slight gap exists between edge of the swing check valve and straightedge under the hinge.
(4) Push down on the swing check valve at hinge and check that gap closes with little effort and opens when force is removed.
(5) If gap does not exist or if force required seems excessive, loosen hinge adjusting screws and move hinge up or down as required.
(6) Tighten adjusting screws