Are flare nuts permitted for underground propane piping installations?

Are flare nuts permitted for underground propane piping installations?

• A. Flare nuts are allowed underground
• B. Only if rated for underground use
• C. Flare nuts can be used above ground only
• D. Flare nuts cannot be used underground

Answer: (D)

Underground propane piping must use fittings that are specifically rated for burial. A flare connection relies on a flare seat and a nut to seal, and while reliable above ground, these joints aren’t considered durable or easily inspectable once buried. Soil moisture, movement, corrosion, and the difficulty of leak testing underground all increase the risk of leaks over time. Because of these safety and maintenance concerns, flare nuts are not permitted for buried piping. If a joint is to be buried, it must be made with fittings that are approved for underground use, ensuring long-term integrity and traceable leak protection.

Underground propane piping must use fittings that are specifically rated for burial. A flare connection relies on a flare seat and a nut to seal, and while reliable above ground, these joints aren’t considered durable or easily inspectable once buried. Soil moisture, movement, corrosion, and the difficulty of leak testing underground all increase the risk of leaks over time. Because of these safety and maintenance concerns, flare nuts are not permitted for buried piping. If a joint is to be buried, it must be made with fittings that are approved for underground use, ensuring long-term integrity and traceable leak protection.