Combination pipe, with outer and inner pipes forming the main opening through it, has additional conduit openings in the pipe wall to carry cables or fresh or waste water and the like

摘要

The combination pipe (1) structure has a circular outer cross section and a main pipe opening (4). At least one further circular pipe opening (12) is within the outer diameter (3) of the pipe, but through the thick pipe wall (7) outside the main pipe opening, and with a smaller clear width than the main opening. The pipe is composed of an outer pipe (14) and an inner pipe (15) which wholly clads the interior surface of the outer pipe.