Tennessee Code Title 7. Consolidated Governments and Local Governmental Functions and Entities § 7-36-119

(a) The authority shall not be operated for gain or profit or primarily as a source of revenue to the associated municipality or any other person or entity. The authority shall, however, prescribe and collect rates, fees, or charges for the services, facilities, and commodities made available by the authority, and shall revise such rates, fees, or charges from time to time whenever necessary so that each system, or any combined systems as authorized in this chapter, shall be and always remain self-supporting, and shall not require appropriations by the associated municipality or any other municipality, this state, or any political subdivision of this state to carry out the authority's purpose. Any one (1) system of the authority shall not subsidize any other system, unless the systems are operated as a combined system in accordance with the terms of this chapter, in which case the combined system shall be self-supporting. The authority shall keep books and records as may be required to properly account for the reasonable distribution of joint or common expenses between the systems of the authority.

(b) The rates, fees, or charges prescribed for each system shall be such as will produce revenue at least sufficient: