Abstract: A pipe fitting is connected in a conduit from a source of fluid under pressure. The pipe fitting comprises a tubular body defining an elongate interior chamber open at both an upstream end and a downstream end. The wall of the body defines a plurality of radial passages opening into the interior chamber and extending through the wall at an acute angle relative to the longitudinal axis of the body. The passages open to the atmosphere through the wall axially spaced upstream from the passage openings into the interior. Fluid flows through the body from the upstream end to the downstream end without escaping through the passages. When fluid flow is blocked downstream of the body, backflow of fluid is directed radially outwardly and angularly upstream through the passages to the atmosphere.