Abstract: A non-return valve (10), typically of commonly called duckbill valve shape, comprising a valve body (12) and a valve membrane (14). The valve body (12) is generally tubular and includes an elongate passageway (16) with inlet (18) and outlet (20) at opposing ends. The valve membrane (14) is of a generally conical-shaped diaphragm formed integrally with the valve body (12). The diaphragm (14) has a collapsible opening or aperture (22) located at or adjacent the cones apex. The conical diaphragm (14) is oriented with its apex pointing downstream. The resiliently flexible material from which the diaphragm (14) is constructed, ensures that the diaphragm (14) in a collapsed condition obstructs or closes the aperture (22) to prevent fluid flowing in a reverse direction, i.e. backflow towards the inlet.