The following measures shall be used to determine sewer charges provided by Section 923.02 (except with respect to subsection (e) and the air conditioning rate provided in subsection (f) of such section) upon all premises served by the system:
(a) On all premises using water exclusively supplied by the City, water consumption on the premises shall be measured by water meter acceptable to the Director of Public Safety and Service.
(b) On premises using water supplied either in whole or in part from sources other than the waterworks system of the City, the Director may require the owner or other interested party to install water meters satisfactory to the Director to the extent necessary to measure all such supplies of water and the quantity of water consumed on the premises shall be deemed to be the aggregate amount disclosed by the meters.
(c) In the event it can be shown to the satisfaction of the Director with respect to any premises, that a portion of the water from any source consumed on the premises does not and cannot enter the system, then in each such case the owner or other interested party may, at his expense, install and maintain separate metering devices to the extent necessary to demonstrate to the satisfaction of the Director the portion of the water consumed on the premises which is discharged into the system, which portion shall constitute the basis for measuring the sewer charge for the premises under Section 923.02.
(1957 Code §16-22)