Tennessee Code Title 7. Consolidated Governments and Local Governmental Functions and Entities § 7-35-414

(a) The governing body of any city or town acquiring and operating a waterworks or sewerage system under this part has the power, and it is the governing body's duty, by ordinance, to establish and maintain just and equitable rates and charges for the use of and the service rendered by the waterworks or sewerage system, to be paid by the beneficiary of the service. The rates and charges shall be adjusted so as to provide funds sufficient to pay all reasonable expenses of operation, repair, and maintenance, provide for a sinking fund for payment of principal and interest of bonds when due, and maintain an adequate depreciation account, and the rates and charges may be readjusted as necessary from time to time by amendment to the ordinance establishing the rates then in force. Any upward adjustment of rates and charges for sewage services shall not be granted solely on the basis of increases of rates and charges for water services, but shall be made only after a finding by the governing body that such an adjustment is reasonable and justified; provided, that this restriction on any upward adjustment of rates and charges for water services shall not apply to counties with a metropolitan form of government. A copy of the schedule of the rates and charges so established shall be kept on file in the office of the board having charge of the operation of such works, and also in the office of the city or town clerk, and shall be open to inspection by all interested parties.

(b) If any municipality in Tennessee adopts a sewer fee ordinance which includes a minimum base rate charge payable by all sewer users, it is declared the public policy of the state that such minimum base rate charge shall be considered to be a local tax upon sewer users in the same manner that local property taxes are so considered. However, user fees paid in excess of the minimum base rate charge that are related to the volume or strength of sewage discharged shall be considered as user fees in the same manner in which electrical, gas, or water consumption is related to actual use.