18" x 20' Corrugated Dual Wall Solid Pipe. Dual wall pipe combines a corrugated outer wall for exceptional strength and a smooth inner wall for outstanding hydraulic characteristics. Springfield Plastics, Inc. dual wall pipe combines a corrugated outer wall for exceptional strength and a smooth inner wall for outstanding hydraulic characteristics. This allows the dual wall pipe to be buried as shallow as 1 foot and as deep as 29 feet with Class I backfill compacted to 90% Standard Proctor Density. Dual wall pipe, manufactured from tough high-density polyethylene, is highly inert and resists rust and corrosion significantly better than competitor materials. The use of dual wall plastic pipe is recommended where discharge water contains floating debris and materials. The primary use of dual wall pipe is to convey water for underground non-pressure applications such as storm sewers, highway underdrains, drainage outlets, roadway culverts and farm drainage main lines.