Pipe Laying Fundamentals

For a distribution operator, installation of your pipe material is an extremely important factor. It will have many effects on how well your system will run on a day-to-day basis. If not installed correctly, many problems may occur. Below are a few things that should be considered during the installation process.

Water mains should not be placed in the same trench with sewer lines. If the sewer pipe isleaking, as they often do, a water main could be surrounded by contaminated soil. If a break were to occur in that water main, a serious health hazard could be in the making.

Waterlines should be laid at least two feet above and two feet laterally from the sewer line. If the water and sewer lines are at the same elevation, they should be at least 10 feet apart. Whenever a water line crosses a sewer line, the water line must be at least three feet above the sewer line and should not contain any pipe joints, except pressure joints on either side of the pipe crossing.

When pipelines are installed under roads, railroads, etc., the pipe should be installed in a way that allows for the accessible repair or replacement of that pipe. Casing or casement pipe is required to protect the water line from loads and stress.

Bedding is usually considered to be the material in which the pipe is partially or fully embedded and serves as its foundation. It increases the load-bearing capability of the pipe. The trench bottom should be correctly leveled and compacted to ensure continuous, firm support throughout its length. Granular bedding material may be used to facilitate a true grade on an imperfect or undercut trench bottom. It can also be used to arrange material to accommodate the pipe bells. Granular material is crushed rock aggregate with 1/4–3/4 inch particle size.

The bedding material should be well-graded material, uniform in size and not containing rocks or other materials that cannot be graded uniformly.

Backfilling is to provide support for the pipe, provide lateral stability between the pipe and the trench walls and to form a cushion around the pipe to protect it from potential damage. The backfill material should be clean and dry and small enough to fill voids and effectively protect the pipe.

The material should contain enough material to be compacted properly to viably protect the pipe. Larger rocks, debris and frozen material should not be used to backfill. Fill the trench in stages and compact as each layer is installed. Tamping can be achieved by hand, mechanically or by saturation.

The correct laying of pipe is one of the most important things that you as operators do. If it is done correctly, deep enough and wide enough, laid with care and backfilled correctly with the proper bedding, the pipe should last its estimated lifespan.

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