In all buildings in which any building drain is too low to permit gravity flow to the public sewer, sewage carried by such a drain shall be lifted by artificial means approved by the director of public works and discharged into the building sewer. (Ord. 1706 § 14.90.910, 1989; Ord. 781 § 2, 1975; Ord. 147 § 6.05, 1963)