Piping which returns vapors to the UST must provide a clear unobstructed path and have a uniform slope of at least _____ drop back to the tank.

The requirement for piping that returns vapors to the Underground Storage Tank (UST) stipulates that it must provide a clear and unobstructed path with a uniform slope to facilitate the efficient movement of vapors back to the tank. The specified drop of at least 1/8 inch per foot ensures that there is sufficient gravitational force assisting in the flow of vapors, preventing any potential blockages or stagnation within the piping system.

A slope of this magnitude is typically sufficient to encourage proper drainage and movement of vapors, which is crucial for maintaining system functionality, preventing hazardous build-up, and ensuring effective vapor recovery. A more significant drop, such as 1/4 inch, 1/2 inch, or 1 inch per foot, while potentially aiding in flow, may not be necessary or could complicate the installation process without offering additional benefits. In contexts where the system is properly designed, the 1/8 inch per foot rule strikes a balance between practical flow requirements and operational efficiency.