(a) Except as provided for liftboats by § 134.180 of this subchapter, each fitting, flange, valve, and run of piping must meet the applicable requirements of part 128 of this subchapter. Piping must be-(2) At least extra-heavy schedule; or(3) Of a suitable corrosion-resistant material.(b) Each distribution cut-off valve must be marked in compliance with § 131.820 of this subchapter.