65 ILCS 5/11-129-6

Rates charged for water by such a municipality shall be sufficient at all times to pay the cost of operation and maintenance, to provide an adequate depreciation fund, and to pay the principal of and interest upon all revenue bonds issued under this Division 129. The holder of such a bond, or of any of its coupons, in any civil action mandamus, injunction or other proceeding, may enforce and compel performance of all duties required by this Division 129 including the making and collecting of sufficient water rates for the specified purposes and the proper application of the income therefrom.