Are PVC insert fittings suitable for underground applications?

Yes, PVC insert fittings are suitable for underground applications. They are commonly used in irrigation systems.

The better question to ask yourself is whether they are the “best” option for the project. It is the responsibility of the system designer and or AHJ (Authority Having Jurisdiction) over the project to approve products and materials. It is also their responsibility to make sure that the product meets all the applicable plumbing and building codes for the area.

PVC insert fittings are quite durable and corrosion resistant, however metal insert fittings, like 304SS or NL bronze insert fittings, will provide greater structural integrity. Metal insert fittings also have higher impact resistance and the ability to withstand mechanical stressors on the fitting. It may be advised against using galvanized or zinc plated insert fittings for buried water lines as they will be more susceptible to corrosion.

If cost is the driving factor in the selection process, PVC insert fittings are an excellent choice. Otherwise, one should consider NL bronze insert fittings. They offer the best combination of corrosion resistance and structural strength. 304SS can also be a good option, however one must make sure that the soil is brackish soil with a high saline content. This can affect 304SS to varied degrees. Saline soils are usually categorized into three types, saline, sodic, and alkaline sodic soils.

CAUTION: Great care must be taken when back filling buried PVC fittings or pipe. PVC is more apt to break if impacted by rocks or stones. A sufficient layer of sand should be placed around and over the piping to protect it from impact damage from rocks and stones dropping into the trench. One must also avoid stressing the PVC fitting(s) by making bends in the piping too close to the fitting which could result in breakage.

WARNING: Never use gear clamps that are not ALL 300 series stainless steel for direct burial applications. The Boshart 2-SSC87 series clamps are ideal for buried water line connections. Clamps with any component, band, housing or screw that is carbon steel, or 200 or 400 series stainless steel, should not be used in direct burial application.

Additional Resources:

https://support.boshart.com/what-to-consider-when-selecting-a-plastic-insert-fitting

https://support.boshart.com/how-to-make-a-secure-connection-between-a-barbed-insert-fitting-into-poly-pipe-using-gear-clamps

https://support.boshart.com/barb-o.d.-dimension-for-poly-pipe-pe-insert-fittings

https://support.boshart.com/what-is-the-pressure-temperature-ratings-for-nylon-polypropylene-pvc-insert-fittings

https://support.boshart.com/do-you-have-chemical-resistance-information-on-the-plastic-insert-fittings

https://support.boshart.com/insert-fitting-pull-off-resistance-testing

https://support.boshart.com/pressure-temperature-ratings-for-bronze-insert-fittings

https://support.boshart.com/pressure-temperature-ratings-for-304-stainless-steel-insert-fittings