Any interconnection of piping systems which are supplied through separate service meters should be avoided. If necessary, as when an appliance such as a laundry stove or drier is installed for the joint use of tenants of a building, a special pipe from each tenant's meter should be installed to the room where such appliances are located and a header provided adjacent to the appliance. Each pipe shall be provided with a lock cock at a point near the header, and each such cock shall be labeled with a metal tag wired in place or with a suitable device indicating the number of the tenant's apartment or other designation for identification. Not more than one illuminating fixture should be supplied from such header in addition to the fuel appliance. The owner of the building shall supply the locks for each cock, thus preventing the removal of the lock when the tenant leaves the premises. (Ord. 15.28)