A valve assembly includes first and second conduits having respective first and second flanges in abutment with each other, a stopper in the second conduit, and a valve body secured between the first and second flanges. The valve body includes a body bore in communication between the first and second conduits. The body bore defines a circular opening in one end of the valve body. The valve body also includes a circumferential notch that substantially insulates the circular opening from distortion arising from securing the valve body. The stopper snuggly seats against the circular opening to prevent fluid flow from the second conduit to the first conduit, but unseats to permit fluid flow from the first conduit to the second conduit. An o-ring may surround a portion of the valve body and be energized as the valve body is secured. A lip may surround the circular opening to provide a seat for the stopper.