PVC and CPVC piping can be installed underground, but the installation must follow all ordinances, regulations, and codes. If you're planning on installing PVC and CPVC piping, make sure to pay special attention to local pipe installation techniques since it will be installed deep within a wide range of sub soils.
The information in this article applies to PVC and CPVC piping installed with solvent cement. This article examines how deep the piping must be buried and will give other essential information about PVC and CPVC piping installation.
Handling and Storing PVC and CPVC Piping
Keep the following in mind when handling and storing piping:
- Store thermoplastic piping in an area where it won't reach high temperatures. If it's exposed to elevated temperatures, it can distort and become damaged.
- Keep PVC and CPVC piping stored in a place where it won't become warped or be subject to external weight or pressure.
- When installing the piping, don't drag it across the ground or harm it.
Before Installation
Inspect the piping for damage before installing. If there are any scratches, holes, or any other damage, the damaged areas must be cut out and thrown away.
Trench Construction
The following underground non-pressure applications should be handled by an engineer or by following the ASTM D2321 standard practice regulations for installation of thermoplastic piping:
- Bedding
- Compaction
- Haunching
- Trench construction
- Initial and final backfill
If your installation project involves a pressure application, follow the guidelines and regulations under ASTM D2774.
When installing, the trench should be wide enough to allow for convenient installation, but it should also be as narrow as your application will allow. Join the piping before inserting it into the trench and place it into the trench after you develop adequate joint strength. Keep in mind that the width of the trench must be wider than the piping when taking expansion from heating and contracting into account.
Note: Cure times for the solvent cement will vary. Refer to the manufacturer's instruction manual for recommended cure and set times.
Pipe Depth
Amount of depth should be calculated by intended service, application, and local weather conditions. If piping liquids are susceptible to adverse weather conditions such as extreme heating or freezing, it should be laid no less than 12 inches below the max freeze level. If the pipelines will be utilized often, the least amount of cover they should have is 24 inches. For low traffic applications, 12 to 18 inches is sufficient. The stress of the bearing load should be determined for larger sizes.
It's highly recommended to install any thermoplastic with a metal or concrete casing when it's installed beneath surfaces that are subject to a lot of traffic, i.e. roadway applications. Piping should be designed to ensure adequate load handling.
Keep in mind that the end of the trench should be smooth and should not have any abnormalities such as rock in or around it. If there are rocks or boulders, cushion the bottom of the trench using four inches of sand or earth below the piping.