Pressure Vessels are containers which are designed to hold liquids, vapors, or gases at high pressures, usually above 15 psig. Examples of common pressure vessels used in the petroleum refining and chemical processing industries include, but are not limited to, storage tanks, boilers, and heat exchangers. Each individual vessel has its own operating limits built in by design that it has to work under, referred to as its design pressure and design temperature. Operating outside of these limits could damage the equipment and potentially lead to loss of containment or catastrophic failure. A Storage Tank is a container for storage of water, oil, gas and petrochemical products for domestic and industrial uses. Storage tanks are available in many shapes and sizes. They can be vertical, horizontal, underground and portable, and can be made from plastic, steel, fiberglass, stone or concrete. Water tank leakage and corrosion, as well as bacterial growth, are threats to the tank.