Abstract: An extruded plastic drainage pipe having long narrow drainage openings with a width of about one eighth inch to limit the flow of particulate matter through the openings and into the pipe. The circumferential extend of the trough is greater than that of the roof and the thickness of both the roof and trough decrease from either side of the centers thereof. The lips of the trough join the roof at approximately 90.degree. to provide a construction particularly adapted to withstand high loading forces without collapse.

Abstract: An underground drainage pipe having a trough, a roof and wings extending outwardly and downwardly from the junction between the trough lips and the roof. Specialized water intake holes are formed through the thickness of the trough lips beneath the wings. The drain pipe may be formed from extruded uniform cross section stock having alignment means for orienting bits used to drill the drainage holes.

Abstract: A coupling for joining spiral underground drainage pipes includes a cylinderical body with an inner circumferential flange and locking projections. When the coupling is rotated on to the drainage pipes the ends of the pipes are held flush on the flange and the inner surface of the flange forms a smooth continuation of the inner surfaces of the pipes.

Abstract: A coupling for joining lengths of underground drainage pipe without inhibiting the flow of water into or along the pipe.