14.01 Where is double wall piping required?

Double wall piping is required by nearly all regulations for underground fuel piping. Aboveground piping is often required to be double contained by State and local regulations – however, requirements vary widely. NFPA 30 requirements for piping allow for single wall piping, however, piping within walls or otherwise inaccessible needs to have welded pipe joints.

In practice, most technical building have double wall piping within buildings for all piping that can contain fuel. Vent piping is typically single wall.