Owners of buildings desiring to use both the City water supply and a supply of water other than that furnished by the Bureau may obtain water service only upon the following conditions. An approved backflow prevention assembly must be installed on the service connection to the premises as outlined in the Bureau's "Backflow Assembly Installation Requirements." If water from a supply other than that provided by the Bureau is found without proper backflow protection the City water supply to the premises shall be immediately shut off with or without notice. In case of such discontinuance, service shall not be reestablished until satisfactory proof is furnished that the cross connection, or potential cross connection has been completely and permanently eliminated or that an approved backflow prevention assembly commensurate to the degree of hazard has been installed on the service connection to the premises, and the assembly has been inspected, tested, and registered with the Bureau.