To determine the sewage flow from any establishment, the Sanitary Board may use one of the following methods:
(a) The amount of water supplied to the premises by the City or a private water company as shown upon the water meter if the premises are metered;
(b) If the premises are supplied with river water from private wells, the amount of water supplied from such sources may be metered at the source or metered at its point of discharge prior to entry into the City sewer;
(c) If such premises are used for an industrial or commercial purpose of such a nature that the water supplied to the premises cannot be entirely discharged into the sewer system, the estimate of the amount of sewage discharged into the sewer system made by the Sanitary Board from the water, gas or electric supply, or metered at its point of discharge prior to the entry into the City sewer;
(d) The volume of sewage discharged into the sewer system as determined by measurements and samples taken at a manhole installed by the owner of the property served by the sewer system at his own expense in accordance with the terms and conditions of the permit issued by the Sanitary Board pursuant to this section; or
(e) A figure determined by the Sanitary Board by any combination of the foregoing or by any other equitable method.
(1977 Code Sec. 13.13)