What material is specified for back-filling around piping?

The specified material for back-filling around piping is clean sand or gravel because these materials provide excellent drainage and support for the pipes. The use of clean sand or gravel ensures that there is minimal risk of water pooling around the piping, which can lead to corrosion or other deterioration over time. Clean sand and gravel also reduce the likelihood of soil compaction and shifting, which can apply undue stress to the piping, potentially leading to breaks or leaks.

In addition, using clean materials helps to prevent the introduction of contaminants that could negatively affect the integrity of the piping, especially in installations related to underground storage tanks (USTs). The requirement for cleanliness also complies with industry standards and regulations meant to protect environmental conditions and maintain the longevity of the infrastructure. Overall, the choice of clean sand or gravel aligns with best practices in piping installation and retrofitting, ensuring the system remains functional and safe throughout its operational life.