(65 ILCS 5/8-4-18) (from Ch. 24, par. 8-4-18)
    Sec. 8-4-18. Rates charged for service and the use of the utility or facility shall be sufficient at all times to pay the cost of operation and maintenance, provide an adequate depreciation fund and pay the principal of and interest upon all revenue bonds which by their terms are payable solely from the revenues derived from the operation of the utility or facility.
(Source: Laws 1961, p. 576.)