Inside leaders must be constructed of cast-iron, galvanized, genuine wrought, steel or copperized iron pipe, with roof connections made gas and water tight. Outside leaders may be sheet metal, but they must connect with house drain by means of a cast-iron pipe extending vertically five (5) feet above grade level, where the building is located along public driveways or sidewalks. Where the building is located off building line, and not liable to be damaged, the connection shall be made with iron pipe extending at least one foot above grade level.
53 P.S. § 4620