65 ILCS 5/11-129-5

Whenever revenue bonds are issued under this Division 129, sufficient revenue received from the operation of such a waterworks or water-supply system shall be deposited in a separate fund designated as the water fund of the municipality. It shall be used only (1) to pay the cost of operation and maintenance of the system, (2) to provide an adequate depreciation fund, and (3) to pay the principal of and interest upon the revenue bonds of the municipality issued under this Division 129.