Abstract: A check valve for deterring intrusion into drain pipes comprises a body member having at least a first orifice and configured to mount on a drain pipe wherein the drain pipe is adapted to promote fluid flow in a single direction. Pivotably mounted on said body member will be a valve member. The mounting arrangement will provide a closed position that substantially occludes the first orifice and a range of open positions when the valve member is pivoted to open in the flow direction. In addition, at least one additional orifice is provided in either the body member or the valve member to permit fluid flow irrespective of the position of the valve member.