60 ILCS 1/205-150
If, before July 18, 1972, a township (i) has constructed or acquired a waterworks system or a sewerage system, or combined waterworks and sewerage system, to serve a particular locality within the boundaries of the township, (ii) has kept separate books, records, and accounts for the system or systems, (iii) has collected rates and charges for use and service from the users of the system or systems that are different from those collected for any other system or systems, and (iv) has paid solely from the income and revenue derived from the operation of the system or systems the principal of and interest upon revenue bonds, the proceeds of which were used to pay the cost of the construction, purchase, improvement, or extension of that system serving a particular locality, all those acts of the township are hereby declared to be valid, and the township may continue so to act, provided the income and revenue of that system serving a particular locality are sufficient to make the payments of principal and interest as they become due. Nothing in this amendatory Act of 1972 (Public Act 77-2083) shall be construed to impair the obligation of the ordinance authorizing the issuance of the revenue bonds.
60 ILCS 1/205-150