70 ILCS 3705/22
Rates and charges for the use and service of the waterworks properties acquired by any district organized under the provisions of this Act shall be sufficient at all times to pay the cost of maintenance and operation, to pay the principal of and interest upon all revenue bonds issued under the provisions of Section 16 of this Act, and to provide a reasonable depreciation fund as established pursuant to the provisions of the ordinance authorizing the issuance of any such revenue bonds, and the holder of any bond or bonds or any of the interest coupon or coupons of any revenue bonds of any such district may in any civil action, mandamus, injunction or other proceeding enforce and compel the performance of all duties required by this Act and the covenants and undertakings set forth in any bond ordinance, including the making and collecting of sufficient rates and charges for the use or service of the waterworks properties of the district, and the proper application of the income and revenue therefrom.
70 ILCS 3705/22