A separate and independent building sewer shall be provided for every building, except where present sewer structures are in use; and except that where one building stands at the rear of another on an interior lot and no private sewer is available or can be constructed to the rear building through an adjoining alley, court, yard, or driveway, the building sewer from the front building may be extended to the rear building and the whole considered as one building sewer.
(1980 Code. Sec. 50.38)