What is the smallest size gas piping buried underground?

What is the smallest size gas piping buried underground?

• A. 1/2 inch
• B. 3/4 inch
• C. 1 inch
• D. 1 1/4 inch

Answer: (B)

The thing being tested is why buried gas piping has a minimum size. In NFPA 54, underground piping is required to be at least three-quarters of an inch in diameter. This minimum helps ensure the pipe is robust enough to withstand soil pressures, corrosion risks, and potential damage, while also providing a practical limit that keeps gas delivery reliable over distance without excessive pressure loss. Smaller underground piping—such as half an inch—would be more vulnerable to damage, more difficult to test and protect, and could lead to insufficient flow for typical residential loads. Larger sizes are allowed, but the question asks for the smallest size that can be buried, which is three-quarters of an inch.

The thing being tested is why buried gas piping has a minimum size. In NFPA 54, underground piping is required to be at least three-quarters of an inch in diameter. This minimum helps ensure the pipe is robust enough to withstand soil pressures, corrosion risks, and potential damage, while also providing a practical limit that keeps gas delivery reliable over distance without excessive pressure loss.

Smaller underground piping—such as half an inch—would be more vulnerable to damage, more difficult to test and protect, and could lead to insufficient flow for typical residential loads. Larger sizes are allowed, but the question asks for the smallest size that can be buried, which is three-quarters of an inch.