Transfer Tank Rules: Diesel, DOT Requirements and Approved Liquids
Questions about what a transfer tank can carry often sound simple: Is it DOT approved? Can it carry gasoline? Can it feed the truck? The accurate answer depends on the product documentation and the complete use case. Start with the manufacturer's stated application, then verify the rules that apply to the vehicle and operation.
Diesel Is Not the Same as Gasoline
Transport rules distinguish between materials based on their properties, quantities and use. Diesel is generally treated as a combustible liquid, while gasoline is a flammable liquid. Combustible and flammable liquids do not fall under the same regulations. Therefore, a tank designed for diesel and non-flammable liquids cannot be assumed suitable for gasoline simply because both are fuels.
The same caution applies to blends and additives. Confirm compatibility for the diesel grade or biodiesel blend you intend to carry, including effects on coatings, seals, pumps, filters and hoses.
Transfer Tank vs. Auxiliary Fuel Tank
A transfer tank carries liquid so it can be dispensed into equipment. An auxiliary fuel tank is connected to the vehicle's fuel system to extend driving range. Those functions are not automatically interchangeable, and a safe dispensing tank is not necessarily approved as an auxiliary feed tank.
Do not connect a WEATHER GUARD Transfer Tank to the truck's factory fuel system. A connection can change the regulatory, emissions, installation and vehicle-warranty considerations.
What "Meets DOT Requirements" Does and Does Not Mean
The DOT requirements vary depending on the liquid type and volume of liquid being transported. For example, combustible fluids of 119 gallons or less do not require DOT HazMat certifications or special tank certifications.
It is up to the operator to determine which requirements apply based on the liquid, quantity, vehicle class, commercial use, route and jurisdiction. State and local fire, environmental and transport rules may add obligations. Product compliance does not replace correct mounting, securement, labeling, operation, inspection or documentation.
Five Questions to Answer Before Transport
- Is the exact liquid approved? Check current product documentation rather than relying on a general category or a competitor's claim.
- Is the tank being used as designed? Treat a dispensing transfer tank differently from an auxiliary vehicle-fuel system.
- Is the installation correct? Secure mounting, venting, compatible dispensing components and leak-free operation remain essential.
- Does the loaded truck remain within its ratings? Include the tank, liquid, pump, people, tools and cargo in payload and axle calculations.
- Which regulations apply to this trip? Review federal, state and local requirements for the vehicle, liquid, quantity, route and business use.
Safe-Use Fundamentals
- Carry only liquids approved for the exact tank and dispensing system.
- Keep the tank vented as designed; never block the vent or intentionally pressurize the tank.
- Keep ignition sources away from fueling and dispensing operations.
- Inspect the tank, cap, mount, pump, filter, hose and nozzle for damage or leaks before use.
- Secure the truck, control spills and follow the liquid supplier's safety information.
- Stop using any tank that leaks, shifts or shows structural damage.
Where to Verify the Rules
Use current primary sources: the WEATHER GUARD model instructions and warranty, the eCFR text for applicable federal rules, vehicle manufacturer information and the authorities that regulate transport and fire safety in the states and localities where the truck operates. For commercial or unusual applications, consult a qualified compliance professional.
Review Product Information Before You Haul
Compare the redesigned WEATHER GUARD tanks and confirm the documentation for the model and liquid you plan to use.