Resources › Tanks & Transport
Diesel Fuel Trailers:
Compliance, Sizing and Selection
The tank is the easy part. What should decide the purchase is the tow vehicle, the trailer build underneath, and how the fuel gets used at the other end.
- Self Bunded or Single Skin
- Sizing
- Compliance
- What to Ask
A diesel fuel trailer puts bulk fuel where the machinery is, and the decision comes down to three things. Whether you need a self bunded tank or a single skin one, which is a site and spill risk question rather than a fuel question. What size you can actually tow, which is set by your vehicle rather than by what you would like to carry. And what the trailer itself has to meet, which comes from it being a trailer on a public road, not from the diesel it carries.
Diesel is generally not a dangerous good for road transport, so the compliance conversation around a fuel trailer is not the one most people expect. It is largely the ordinary trailer conversation: registration, brakes, coupling ratings, load restraint and tow capacity. That is covered in more depth in our guide to how much diesel you can legally transport.
What follows is the selection side of it: the two tank constructions and when each is right, how to size a trailer against a real tow vehicle, what the trailer build should include, and the questions that separate a trailer built for the job from one that merely holds fuel.
0.83 kg Per litre of diesel. A 1,500 litre trailer is well over a tonne of fuel before the trailer
Tow first The vehicle's rated capacity, not the tank size you want, sets the ceiling
Bunding Is a site and spill decision. It is what most sites specify and many require
Self Bunded or Single Skin
This is the first fork, and it is decided by where the trailer will stand rather than by what it carries.
A self bunded tank is a tank inside a second, outer tank. If the inner one leaks, the fuel is caught in the space between the two rather than reaching the ground. A single skin tank is one wall, so a breach releases fuel directly.
- Self bunded suits sites where a spill would reach soil, stormwater or a waterway, where an environmental approval or a client's site rules require secondary containment, and anywhere the trailer sits unattended for long periods. Most commercial and civil sites specify it, and a good number will not let a single skin trailer through the gate.
- Single skin costs less and weighs less, which means more usable payload for the same tow rating. It suits lower risk settings, typically farm and lighter duty use on private land where the operator controls the site and the spill risk is assessed as low.
A-FLO's trailer range runs both, with self bunded FUELTRANS trailers and single skin poly trailers in the diesel fuel trailers category.
Ask the site before you buy the trailer
If the trailer will go onto client sites, mine sites or government projects, their requirements decide this, not yours. A single skin trailer that cannot enter the site it was bought for is an expensive lesson, and it is a phone call to avoid it.
Sizing It Against a Real Tow Vehicle
The common mistake is choosing the tank first. Work the other way, because the vehicle sets a ceiling you cannot negotiate with.
Diesel weighs roughly 0.83 kg per litre, so the fuel alone in a 1,200 litre trailer is close to a tonne, and the trailer, pump and fittings sit on top of that. The figures that constrain you:
| Figure |
What it limits |
| Braked towing capacity |
The maximum loaded trailer weight the vehicle may tow. Check the compliance plate and the manufacturer's figure, not a general spec for the model |
| Tow ball download |
The vertical load the coupling may carry, often a percentage of trailer weight. A full fuel trailer loads it heavily |
| GCM |
Gross combination mass, the total for vehicle plus trailer. It is common to be inside towing capacity and still over GCM once the ute is loaded |
| GVM |
The vehicle's own maximum, which the ball download counts against |
| ATM and GTM |
The trailer's own rated maximums. Buying a trailer rated above what you tow with is not a problem; loading it beyond its rating is |
| Licence class |
Heavier combinations can move into a different licence class and into heavy vehicle obligations |
Size on the trip, not the tank
A trailer you can only tow half full is a trailer bought too big. Work out how much fuel a run actually needs and how often you are willing to refill, then buy the size that carries it inside your tow figures with margin. Fuel that sits for months in a part-filled tank has its own problems, covered in how long you can store diesel.
What the Trailer Itself Should Have
Most of the compliance burden sits in the trailer rather than the tank, and this is where build quality is either present or absent.
- Braking appropriate to the mass. Above a threshold, trailers require brakes, and heavier trailers require a breakaway system that applies them if the trailer separates. Electric brakes are the usual arrangement and need a controller in the tow vehicle
- A coupling rated above the loaded weight, correctly fitted, with safety chains rated to match
- A chassis designed for a liquid load. Fuel moves, and surge loads a chassis differently from a static weight. Baffles inside the tank reduce it
- Lighting, reflectors and plating to the standard required for a registered trailer, with the compliance plate present and legible
- A jockey wheel and stabilisers that handle the loaded weight, not just the empty one
- Tank mounting engineered to the chassis, not strapped to it
- A spare wheel, because a fuel trailer is often used where a tyre service is hours away
- Lockable fill and dispensing points, since a fuel trailer parked overnight is a target
Registration, roadworthiness and the periodic inspection requirements come from your state road authority and apply because it is a trailer. Confirm them locally rather than assuming they match another state's.
The Dispensing End
A trailer can be supplied bare or built with pumping equipment, and the choice affects both price and how useful it is on arrival.
Bare means tank and trailer only, for operators who already have pumping gear or want to specify it themselves. Built means the trailer arrives with a pump, hose, nozzle and usually a filter and meter, ready to dispense.
What to match: the flow rate to the machines you fill, since filling a large machine through a low flow pump wastes real time; the hose length to how close you can park; an automatic nozzle for anything you fill regularly; and filtration, because a trailer collects water and dirt through its vent and its fill point more readily than a tank standing on a slab. Micron ratings and water separation are covered in our fuel filtration guide, and fittings and accessories cover the rest.
A trailer is a hostile environment for fuel
It is exposed, it is moved, it heats and cools daily, and it is often part filled. That combination drives condensation and water in the tank, which is the precursor to microbial growth. Filtration and a regular water check matter more on a trailer than on a static tank, and the maintenance schedule in our tank cleaning guide applies here too.
Trailer, Ute Tank or Transportable Cube
A trailer is not always the right answer. The three options solve different problems.
- A ute or tray mounted tank keeps the vehicle single, needs no separate registration and is quicker to take anywhere, but it consumes payload the vehicle needs for other things and it is limited in volume
- A trailer moves the weight onto its own axles, frees the tray, and carries far more, at the cost of registration, towing skill, somewhere to park it and a reversing problem on tight sites
- A transportable tank such as a FUELCUBE is designed to be lifted and relocated rather than towed. If the fuel needs to move between sites every few weeks rather than every day, and a forklift or hiab is available at both ends, it often beats a trailer
The distinction worth holding onto: a trailer is for fuel that moves with you daily. A transportable tank is for fuel that relocates occasionally. Buying a trailer for a tank that will sit in one place for a year is paying for axles you are not using. The full diesel systems range covers all three.
Questions Worth Asking Before You Buy
What is my real towing figure
From the compliance plate and the manufacturer, with the vehicle loaded the way it actually gets loaded. Then work out the tank size that fits inside it, rather than the reverse.
Where will this trailer be required to go
If client or mine sites are involved, ask them whether self bunding is mandatory before choosing. Their rules override your preference and they will not bend for a delivered trailer.
What is the ATM, and is it plated
A trailer without a compliance plate and a clear rating is a problem you inherit. Ask for the plate details in writing before purchase, not after delivery.
Bare or built, and what is included
If it is built, get the pump flow rate, hose length, nozzle type and whether a filter and meter are fitted. Those four decide whether it is usable on day one.
Frequently Asked Questions
Do I need a special licence to tow a diesel fuel trailer?
Not because of the diesel. Diesel is generally not classified as a dangerous good for road transport, so carrying it does not by itself trigger dangerous goods driver licensing. What can require a different licence class is the weight of the combination, since heavier vehicle and trailer combinations move into higher classes and can bring heavy vehicle obligations with them. Check the combination mass against your licence class with your state road authority.
Does a diesel fuel trailer need to be registered?
Yes, if it is used on public roads. It is subject to the same registration and roadworthiness requirements as any other trailer in your state, along with coupling, brake, lighting and load restraint obligations. Those requirements come from the fact that it is a trailer rather than from what it carries. Requirements differ between states, so confirm with your own road authority instead of assuming another state's rules apply.
Should I buy a self bunded or single skin fuel trailer?
Decide it on where the trailer will stand rather than on what it carries. Self bunded means a tank within a tank, so a leak is contained instead of reaching the ground, and it suits any site where a spill could reach soil, stormwater or a waterway. Most commercial, civil and mine sites specify it and many will not admit a single skin trailer. Single skin costs and weighs less, giving more usable payload, and suits lower risk farm and private land use.
What size diesel trailer can I tow?
Work from the vehicle rather than the tank. Diesel weighs roughly 0.83 kilograms per litre, so 1,200 litres is close to a tonne of fuel before the trailer itself, plus pump and fittings. Check braked towing capacity, tow ball download, GVM and gross combination mass from the compliance plate and the manufacturer's figures, with the vehicle loaded as it normally is. Then choose the tank size that fits inside those numbers with margin.
Is a fuel trailer better than a ute tank?
They solve different problems. A ute or tray mounted tank keeps everything on one vehicle, needs no separate registration and goes anywhere the ute goes, but it uses payload you may need elsewhere and holds far less. A trailer moves the weight onto its own axles, frees the tray and carries much more, at the cost of registration, parking, and manoeuvring on tight sites. Volume and how often you refill usually decide it.
Do fuel trailers need brakes?
Above a certain mass, yes, and a loaded fuel trailer reaches that threshold quickly because fuel is heavy. Heavier trailers also require a breakaway system that applies the brakes automatically if the trailer separates from the tow vehicle. Electric brakes are the usual arrangement and need a compatible controller fitted in the tow vehicle. The exact thresholds are set by your state road authority, so confirm them for your combination.
How do I stop water getting into a fuel trailer?
A trailer is harder on fuel than a static tank because it is exposed, moved, heated and cooled daily and often part filled, which drives condensation. Keep it as full as practical to reduce the air space, check for water at the lowest point regularly and drain it, keep the fill point and vent sealed and clean, and fit filtration with water separation. Water in the tank is what precedes microbial growth, so removing it early avoids the harder problem.
Can I get a fuel trailer with a pump already fitted?
Yes. Trailers are supplied either bare, meaning tank and trailer only for operators who have their own pumping equipment or want to specify it, or built with a pump, hose, nozzle and usually a filter and meter so they dispense on arrival. If you buy built, confirm the pump flow rate, the hose length, the nozzle type and whether filtration and metering are included, because those four decide whether it is usable on day one.