Abstract: A method is disclosed for forming a substantially flush joint or coupling between two profile wall thermoplastic pipes. The method comprises removing substantially all of the helical rib and inner wall of a first pipe for a distance from an end of the first pipe and removing a portion of the helical rib for a distance from an end of a second pipe. By so doing, the outer wall of the second pipe can be deflected radially inward and the end of the second pipe can thereby be coupled with the first pipe by overlapping the outer walls adjacent the ends of the first and second pipes, with the outer wall of the first pipe being on the exterior. When overlapped, the second walls of both the pipes can then be fused together. Alternatively, the outer wall of the first pipe can be removed rather than the inner wall, and the inner wall of the second pipe deflected radially outward such that the inner wall of the second pipe can be positioned around the inner wall of the first pipe and fused thereto.

Abstract: An improved coupler and method for fusing profile wall thermoplastic pipe in a manner to form a substantially flush joint are disclosed. The improved coupler is preferably configured to be inserted between the inner and outer walls of each of the pipes being joined. The improved coupler preferably has a radial thickness that is less than the radial dimension of the gap or channel that is formed between the inner and outer walls of the pipes being joined and is preferably configured and adapted to have an annular interference fit with one of either the inner or outer walls of such pipe ends. Electrofusion is preferably used to heat-fuse the improved coupler to each of the pipes to create a strong, leak-proof joint between the two pipes.