Manual tank gauging may not be used on tanks more than ____ years old with a capacity of 1,000 gallons or more.

• A. 5
• B. 8
• C. 10
• D. 12

Answer: (C)

The main idea is that large, older tanks require more reliable methods than a manual gauge to track inventory and detect leaks. For tanks with a capacity of 1,000 gallons or more, manual gauging is not permitted once the tank reaches ten years of age. After ten years, the potential for measurement errors increases due to factors like sediment buildup, corrosion, and liquid expansion, so automatic or more precise inventory methods are preferred to ensure accurate monitoring. Ten years is the threshold used, balancing practicality with safety. The other numbers don’t align with this standard, which is why ten years is the best choice.