When metallic piping is buried underground, an electrically insulating (dielectric) fitting must be installed before the entrance of the piping into the building. In no case shall the fitting be located after the connection of a bond wire for use with corrugated stainless steel tubing (CSST) or other piping material.
No flare fittings shall be located underground, unless specifically rated for such use and protected from corrosion in accordance with the manufacturer's instructions.
All underground metallic piping must be protected from corrosion. This may be accomplished by sleeving, using a PVC coated pipe material approved for direct burial, or by other corrosion prevention material listed for such use.
02-658 C.M.R. ch. 14, § 1