How to install HDPE pipe

Dec. 20, 2022

High-density polyethylene (HDPE) is a versatile plastic made from petroleum that is used in many applications, one of which is piping. Also known as polyethylene, this material is used for domestic and agricultural water supply.

HDPE installation can be done in two ways. One option is to dig a trench in which to lay the pipe, while another is to use a commercial auger, which drills through the ground and pulls the pipe at the same time. The latter is recommended for situations where trenching may not be permitted or possible, such as in streets or driveways. Grooved installation, on the other hand, is easier because there is no need to use joints.

Step 1: Trench Construction

It is important to assess site and subsurface conditions prior to trench construction. Also, there should be a specific installation code, especially if the depth is deep and the soil conditions do not support the pipe. For pipe installations of 12" diameter PE pipe and smaller PE pipe, consideration should be given to groove width, length and depth.

Step 2: Trench Floor Preparation

The stability of the ditch bottom is important for supporting the bedding material and can be tested by walking on the ditch. If there are no visible footprints, the ditch floor has stabilized. For unstable ditch bottoms, correct by dehydration. However, if this is not possible, you can add gravel. It is important to make sure the bottom of the ditch is smooth and free of rocks, ridges, cavities and lumps. Remember, where boulders and rocks are present, they will need to be removed.

Step 3: Trench Underfill

It is important that about four to six inches of rammed bedding material be placed on the bottom of the trench. It should also be free of sand, gravel or clay sand.

Step 4: Pipe Laying

The HDPE tubing should be placed by hand at approximately 8 inches in diameter. The equipment should only be used for moving, lifting and lowering as it cannot be dropped, tipped, pushed or rolled into trenches.

Step 5: Pipeline Embedding

To support the pipe into the trench, it should be buried in the soil. To do this properly, embedment materials that include coarse-grained soils such as sand or gravel and coarse-grained soils that may contain clay and silt should be used. Conversely, for corner burials, chip the gravel with a shovel and dump it around the pipe. However, if these materials are naturally occurring, such as sand and fine powder mixtures, they should be in the lift and should not be more than eight inches thick. Once placed, they should be compacted using a mechanical compactor.

Step 6: Trench backfill and compaction

Once the HDPE pipe is in place, the next step is to backfill it to prevent the pipe from falling out of line and protect it from external damage etc. Backfill should be done from the underarm of the pipe to approximately 6 inches above the PE pipe. The lifts should be placed evenly on both sides of the pipe while ensuring that no large, hard objects hit the pipe. For final backfill, there should be at least one foot of backfill cover over the pipe prior to compaction.

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