Oil storage tanks on the inside of any building shall be located in the lowest story, cellar or basement. A total storage of 550 gallons shall be permitted inside of any building but not more than 275 gallons shall be permitted in any 1 storage tank. Where more than 1 storage tank is installed such tanks shall be connected to the main feed pipe leading to the auxiliary tank, or if no auxiliary tank is used, such storage tanks shall be connected with the main feed pipe leading to the burner, with a manually operated three-way valve so that not more than 1 tank can in any way discharge its contents at one time. In cases where conditions make it impossible to install tanks outside buildings, it shall be permissible to install tanks of larger capacity inside buildings subject to the regulations of section 13 hereof. Tanks shall be constructed of galvanized iron or basic open hearth steel or wrought iron, not less than 14 gauge. All joints shall be welded, brazed or riveted. The tanks shall be reinforced with a welded or riveted pad or flange where connections are made. All tanks shall be made tight and tested at 5 pounds air pressure and with soapy water without showing leaks. Tanks shall have rigid and incombustible support and shall not be located less than 5 feet, measured horizontally, from any fire or flame, and shall be placed on an incombustible floor. Glass gauging devices, or any others, the breakage or derangement of which would permit the escape of oil, shall not be used. Fuel oil shall not be forced from such storage tanks by positive air pressure.