US Patent 7451784 Corrugated pipe with perforation protecting cover

A pipe having an axially extending bore is defined by a corrugated outer wall having alternating, axially-adjacent, annular crests and valleys. The wall of the pipe has a hole disposed in a valley which provides fluid communication between the bore and the outside. The pipe also has a cover which extends between and is attached to axially adjacent crests. The cover is disposed over the hole to prevent material in which the pipe may be disposed from obstructing the hole and permitting fluid flow through the hole.