How to Install Corrugated PE Sewer Pipes

Corrugated polyethylene pipe is a common material used to construct underground storm and sanitation sewers. Composed of an inert high density polyethylene, the pipe is lightweight and easier to install than concrete pipe. It also does not rust like steel pipe. Corrugated polyethylene pipe must be installed properly because the pipe depends on pressure from the soil on its sides to support the weight on top of the pipe. Since it is lightweight, PE pipe moves around easily during installation, so extra care must be taken to prevent it from slipping out of place before installation is complete.

Corrugated polyethylene pipe
Corrugated polyethylene pipe couplings
Pipe bedding material (clean gravel or crushed stone, no stone larger than 1 1/2 inch)
Backhoe or hydraulic excavator
Small vibratory compactor (optional)
Builder's level
Pipe laser (optional)
Non-woven geotextile
Shovel
8-foot length of 2-by-4 lumber

Instructions

- 1
  
  Trenching with a backhoe is recommended.
  
  Install the corrugated polyethylene pipe in a trench that is at most 1 foot wider than the widest part of the pipe. The trench should be the same width from the bottom to an elevation of 2 feet over the top of the pipe. While digging the trench, be sure to separate the topsoil from the subsoil so that the topsoil can be replaced and seeded during the restoration process.
  
  The pipe must be buried with at least 2 feet of fill over the top of the pipe, in order to carry the rated loads on the pipe. If you cannot bury the pipe this deep you can raise the grade of the area by filling, or you may be able to lower the elevation of the pipe. The pipe must be placed on 3 inches of bedding material, so be sure to accommodate the bedding depth by increasing the depth of the trench by this amount.
  
  The bottom of the trench must be firm and dry before placing the pipe into it. Remove any mucky or soft soil and replace it with clean gravel before proceeding. Always make sure the trench remains dry while you are placing the pipe into it. You may be able to drain the trench by allowing it to flow to a lower point, or you may need to pump it dry.
- 2
  Just before placing the pipe into the trench, place 3 inches of bedding material in the bottom. The bedding material should be clean gravel or crushed stone and it should compact easily. Shape it to conform to the bottom shape of the pipe.
  
  Install the CPE on top of the bedding and hold the pipe in place with boards or stone so that the bedding can be compacted around the pipe. Finalize the correct grade of the pipe with a builder's level or with a pipe laser installed inside the pipe.
- 3
  
  Crushed stone makes an excellent bedding material.
  
  Compact the bedding around the bottom half of the pipe with a hand tamper or length of 2-by-4 lumber. Then place the bedding material in 6-inch layers on each side of the pipe. You can drop the bedding carefully from a backhoe bucket around the pipe, slowly filling and compacting each side of the pipe equally.
  
  Install the bedding to an elevation of 6 inches above the top of the pipe. A small vibratory compactor can be used once the bedding is above the widest point of the pipe.
  
  Then fill the trench with the soil you removed in Step 1. Grade the soil to its final elevation. For safety reasons and to prevent the pipe from slipping out of place, backfill the trench as soon as possible after installing each section of pipe.
- 4
  
  Use a level to check the grade of the pipe.
  
  Once the previous section is firmly in place, install the next section of pipe. The pipe should be joined using a coupling supplied by the pipe manufacturer and made for the particular brand of corrugated polyethylene pipe you are using. If the pipe is entering a concrete structure, you must carefully mortar it into the structure. Surround the joint at the structure with a non-woven geotextile to prevent soil from entering the joint.
- 5
  In lawn areas, the top 6 inches of fill should be topsoil. After placing the topsoil, seed the trench with grass or install sod. Since the trench may noticeably settle after a few months, be prepared to go back and place a little more topsoil and seed on any low areas that develop.
  
  In previously paved areas, it is a good idea to backfill with clean gravel to 12 inches below the bottom of the pavement. Then place 12 inches of crushed stone or equivalent on the area. Extra care must be taken to compact the fill thoroughly. Then pave the trench with an equal thickness of pavement to the existing pavement. In public areas, the backfill and pavement must conform to local or state regulations.

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