No water pipe of the city water system shall be connected with any pump, well, pipe, tank or any device that is connected with any other source of water supply and when such are found, the city shall notify the owner or occupant to disconnect the same and, if not immediately done, the city water shall be turned off. Before any new connections to the city system are permitted, the city shall ascertain that no cross-connections will exist when the new connection is made. When a building is connected to "City Water" the private water supply may be used only for such purposes as the city may allow.
(1975 Code, § 3.70, Subd. 5)