70 ILCS 2405/7.5

The sanitary district, in addition to other powers vested in it, is authorized to enter into agreements with any city, village or incorporated town located partly within and partly without the territorial limits of the sanitary district and which has a sewage system to receive and dispose of all sewage of such city, village or incorporated town collected by its system; and for such purpose the sanitary district may extend its drains, ditches or sewers to connect with the sewage system of such city, village or incorporated town.