What type of material should be used for piping backfill?

Using clean sand or pea gravel with a maximum size of 3/4" for piping backfill is vital for ensuring proper drainage and support around the piping. This type of material allows for effective water movement, preventing the accumulation of moisture that could lead to corrosion of the pipes or other complications. Clean sand or gravel provides sufficient void space, which helps in minimizing soil settlement around the piping system.

This option also meets industry standards for underground storage tank installations by promoting stability while allowing air circulation, which can help in keeping the piping system in good condition over time. Moreover, the absence of large particles in this backfill material reduces the risk of damage during installation or from external pressures.

Other materials such as a soil and clay mix could retain water and lead to settling issues, recycled asphalt might not provide adequate drainage, and concrete would pose risks of cracking and not allowing required flexibility and expansion of the piping system. Therefore, the use of clean sand or pea gravel is the most suitable choice for backfilling around UST piping.