a co - extruded multi - layer plastic pipe and method of manufacture are disclosed in which a first extruder melts and extrudes a first plastic material into the outer annulus of a coaxial extrusion die to form an outer pipe layer , and a second extruder melts and extrudes a highly oxidation - resistant plastic material into the inner annulus of said coaxial extrusion die under a blanket of inert gas to create an inner pipe layer , whereby the outer and inner pipe layers are fused together under the protection of the inert gas blanket which prevents premature degradation of the oxidation - resistant inner layer until the finished extruded pipe has cooled and solidified .