Which option correctly states the maximum capacity of the vapor dome roof tank?

• A. A maximum of 10,000 gallons
• B. 2,000,000 gallons
• C. 4,000,000 gallons
• D. A max of 8,500,000 gallons

Answer: (D)

A vapor dome roof tank is designed to store a very large volume of liquid while leaving space above the liquid for vapor to vent safely. The dome creates a dedicated headspace so that the tank can handle the vapor produced without building dangerous pressure. Because of this, the maximum design capacity refers to the total volume the tank can hold, including both liquid and that headspace, and for large bulk storage units that capacity runs into the millions of gallons. Here, 8,500,000 gallons represents the largest design volume among the options and aligns with the scale of a bulk storage facility. The smaller figures would correspond to much smaller tanks and don’t reflect the maximum capacity of a large vapor-dome roof tank.