HDPE (high density polyethylene) pipe is a versatile material, used mainly in industrial applications. It is usually black, although a specialized yellow version is used for natural gas piping. It is also usually smooth-walled, although a ribbed version is used frequently in drainage applications. It comes in sizes up to 6 inches in diameter and is supplied in large coils, rather than fixed sections. That is one of its main advantages — it can be rolled out to a needed length, where other pipe must be joined in sections. Every joint is a potential weakness.
■Install HDPE underground one of two ways. Dig a trench, lay the pipe in it and backfill the trench. Or use a commercial auger, a machine which drills through the ground and pulls the pipe after it. This technique is used where driveways, streets or other surface barriers restrict trenching. Trench installation is easier because there are no joints to secure — just roll the pipe into the trench and cover it. Trench installation is frequently used for HDPE drainage or water distribution piping. It is universal for natural gas distribution.
■Place HDPE inside a building in a method similar to installation of any pipe, except there are no seams, elbows or other joints and no pipe sections to be lifted individually. Bend flexible HDPE around heating pipes, chimneys, beams or other obstructions to install it above a ceiling, as in a typical installation to distribute water for fire sprinkler systems or to move water or chemicals throughout a facility.
■Build piping systems for handling chemicals or other liquids in an industrial setting with overhead installations. Uncoil the pipe into the proper layout, running it along walls or up beams to a ceiling. Fasten it with clamps where needed and connect it with heat welding or mechanical connectors, if tying into to other types of piping. Use compression fasteners, which tighten inside the pipe to seal the joint, to connect HDPE with most other types of pipe; HDPE suppliers provide these connectors.
■Connect lengths of HDPE where necessary with heat welding, called "butt fusing." Ends of HDPE pipe are pushed together, then sealed by heating with a torch. A commercial fusing device forms the pipe ends, reaming one side slightly and tapering the other to fit inside; that joint is then welded with heat. Properly heat-fused joints are as strong as the original pipe.