70 ILCS 3705/19

If there be any city, village or incorporated town located within the boundaries of the district which does not own or operate a waterworks system, and such city, village or incorporated town shall adopt an ordinance requesting the district to supply water for public and domestic use within such city, village or incorporated town, then any such district may construct, operate and maintain its waterworks properties within the corporate limits of such city, village or incorporated town for the purpose of supplying water for public and domestic use to the inhabitants thereof.