The following measures shall be used to determine the sewer charges provided by § 51.25(A) upon premises served by the sewerage system:
(A) On premises using water exclusively supplied by the city, and having a water meter acceptable to the Service Director, the quantity of water used, as measured by the meter, shall determine the sewer charge thereon, as provided herein.
(B) On premises either using water exclusively supplied by the city or exclusively supplied from other sources, where the quantity of water used thereon is not measured by a water meter or is measured by a water meter not acceptable to the Service Director, the owner or other interested party shall at his expense install and maintain a water meter acceptable to the Service Director, and the quantity of water used, as measured by the meter, shall determine the sewer charge thereon, as provided herein.
(C) On premises using water supplied both by the city and from other sources, which in either case is not measured by a water meter or is measured by a water meter not acceptable to the Service Director, the owner or other interested party shall at his expense install and maintain water meters satisfactory to the Service Director to measure all such supplies of water, and the quantity of water used to determine the sewer charge thereon shall be the sum of the quantities of water measured by the several meters, as provided herein.
(D) In the event it can be shown, to the satisfaction of the Service Director, with respect to any premises, that a portion of the water from any source used thereon does not and cannot enter the sewerage system, then in each such case, the owner or other interested party may at his expense install and maintain separate water meters where necessary so as to show to the satisfaction of the Service Director that portion of the water used which is discharged into the system, and the quantity of water used, as measured by such meter or meters showing discharge into the system, shall determine the sewer charge thereon, as provided herein.
(`59 Code, § 927.06)