What Is The Difference Between A Pressure Vessel And A Storage Tank: Code, Design and Inspection What is the difference between a pressure vessel and a storage tank? The dividing line is pressure. A pressure vessel is built to hold a gas or liquid at a pressure different from, and usually well above, atmospheric, and it is designed, fabricated and inspected to a pressure-equipment code such as ASME BPVC Section VIII with a stamped nameplate stating its maximum allowable