What standard must supply tanks conform to when installed inside of buildings?

The correct standard for supply tanks installed inside buildings is UL 80. This standard specifically addresses the requirements for the construction and integrity of steel petroleum tanks, ensuring they meet safety and environmental protection regulations when used for storage within a building. UL 80 outlines essential considerations such as tank design, materials, welding, and testing methods to prevent leaks and failures that could pose a risk in an indoor environment.

The other standards mentioned relate to different contexts. NFPA 30 pertains to the storage, handling, and use of flammable and combustible liquids but doesn't specifically focus on the construction standards of the tanks themselves. ASME B31.3 is a standard for piping systems and focuses more on the design and construction of piping rather than tanks. API 650 covers the design and construction of welded tanks for oil storage, primarily for tanks used in outdoor settings rather than inside buildings. Therefore, UL 80 is the appropriate standard for ensuring safety when installing supply tanks within enclosed spaces.