70 ILCS 2605/26
Any city, village or incorporated town located in any such sanitary district which owns a system of waterworks and procures its supply of water from a lake or other source which will be saved from sewage pollution by the construction of the sewage facilities provided by this Act shall furnish water to any city, village, township, incorporated town or other municipal corporation within or outside the boundaries of any such sanitary district in such quantities as may be required to supply consumers within or outside said territory at no greater price or charge than said city, village or incorporated town charges and collects of consumers within its limits through meters for like large quantities; provided, however, that any such city, village, township, incorporated town or other municipal corporation making application for the sale of water to it shall be required to build or cause to be built suitable and sufficient water mains to the corporate limits of such city, incorporated town or village so owning a system of waterworks and supplying water as aforesaid to connect with the water mains and receive the water from such city, incorporated town or village.
However, where such a city, village or incorporated town constructs and operates waterworks facilities such as supply mains, pumping stations, reservoirs and other facilities outside of its corporate limits and within 35 miles of the limits thereof, for the purpose of supplying improved water service to municipalities, townships and water system authorities which request such service, such city, village or incorporated town may enter into contracts with such municipalities, townships and water system authorities at a higher water rate than the existing metered rate for like consumers within such city, village or incorporated town to allow such city, village or incorporated town to obtain a fair return to cover the costs of financing, constructing, operating and maintaining the said improved facilities, and in the event that thereafter such rates are not agreed upon by the parties or are not otherwise provided for by contract, such rates shall be fixed and determined by the Circuit Court of Cook County upon petition filed therein; provided that the right of any municipal corporation within or outside the sanitary district to obtain water from such a city, village or incorporated town at its corporate limits at the existing metered rate for like consumers within the corporate limits of such city, village or incorporated town shall remain unimpaired.
70 ILCS 2605/26