What is the minimum gas piping size for buried installations?

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

Answer: (D)

For buried gas piping, a baseline size is specified to ensure enough flow and to keep pressure drop within reasonable limits in underground runs. The minimum nominal diameter allowed for buried installations is 3/4 inch. This size helps provide adequate gas flow to typical residential loads and aligns with practical installation practices under the ground, including protection and backfill considerations. Smaller diameters would lead to excessive pressure drop and may not meet code requirements for underground piping. Larger sizes can be used if the calculated gas demand or run length requires them, but nothing smaller than 3/4 inch is permitted for buried piping.