Owners of buildings desiring to use both a city water supply and a supply of water other than that furnished by the city water system may obtain city water at applicable rates upon the following conditions and not otherwise. Under no circumstances shall a physical connection, direct or indirect, exist or be made in any manner, even temporarily, between the city water supply and that of a private water supply or between two services connected to the city water supply. Where such a connection is found to exist, or where provision is made to connect the two systems by means of a spacer or otherwise, the city water supply shall be shut off from the premises with or without notice. In case of such discontinuance, service shall not be reestablished until satisfactory proof is furnished that the cross connection has been completely and permanently severed.