What is the maximum capacity of a DOT406/MC306 nonpressure liquid tank?

The maximum capacity of a DOT406/MC306 nonpressure liquid tank is indeed 9,000 gallons. These tanks are designed primarily for transporting nonpressure liquids, such as fuels and other hazardous materials, and have specific construction and operational standards regulated by the Department of Transportation (DOT) and the Pipeline and Hazardous Materials Safety Administration (PHMSA).

In these designs, the capacity is determined based on the structural integrity required to handle liquids without the need for pressure, allowing them to be built with lighter construction materials compared to pressure vessels. The 9,000-gallon capacity is a practical limit that ensures safe handling, transport, and storage of liquid materials while adhering to safety standards.

Other capacities listed, such as 3,000, 6,000, and 11,500 gallons, do not align with the typical specifications for DOT406/MC306 nonpressure tanks, as they either fall below the typical size range or exceed the practical limits for nonpressure transport tanks.