Regulationcurrent
49 CFR 192.373
Service lines: Cast iron and ductile iron.
Current as of 2026-08-18 Government source
eCFR editorial compilationAuthoritative but unofficial
View source (a)Cast or ductile iron pipe less than 6 inches (152 millimeters) in diameter may not be installed for service lines.#
(b)If cast iron pipe or ductile iron pipe is installed for use as a service line, the part of the service line which extends through the building wall must be of steel pipe.#
(c)A cast iron or ductile iron service line may not be installed in unstable soil or under a building.#