Sec. 11. If:
(1) a district is established for the purpose of furnishing water supply for domestic, industrial, and public use or that purpose is added to a district; and
(2) there is within the boundaries of the district a municipality or public utility providing water supply to part of the territory within the boundaries;
the order of the court establishing the district or adding that purpose is territorial authority only for that territory within the boundaries not served by the municipality or public utility.