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Storing Petrol (ULP) On Site: Why the Rules Are Stricter Than Diesel
Petrol is not diesel in a different colour. It sits in a different classification, and that difference decides where a tank can go before it decides which tank you buy.
- Classification
- Siting
- Equipment
- Sizing
Petrol is classified as a flammable liquid and diesel as a combustible liquid, and almost every practical difference in how the two are stored follows from that one distinction. Petrol gives off ignitable vapour at ordinary Australian temperatures, that vapour is heavier than air, and it travels. So siting, separation from boundaries and buildings, control of ignition sources and the specification of the tank and pump are all treated more stringently than they are for diesel. The practical consequence is that the regulatory position should be confirmed before a tank is selected, because it can determine where the tank is allowed to stand.
Plenty of sites that have run bulk diesel for years assume petrol is the same exercise with a different label on the tank. It is not, and the assumption is an expensive one, because the constraint that catches people out is usually not the tank at all. It is the distance between where they wanted to put it and something else on the site.
This article sets out what actually changes when the stored fuel is unleaded, what that means for siting and equipment, and how to size a petrol tank so the fuel keeps moving. It deals with storage. The separate question of what you can legally carry on a road is covered in how much diesel you can legally transport in Australia.
Class 3 Petrol is a flammable liquid. Diesel is a combustible liquid, and that gap drives the whole requirement
600 to 8,000L The GENCUBE ULP range, each supplied with a 12V ULP pump kit and filtration
Position first Confirm the regulatory position before choosing a tank. It can decide where the tank stands
Petrol Is a Different Classification, Not a Different Fuel Grade
The property that separates the two fuels is flash point, the lowest temperature at which a liquid gives off enough vapour to form an ignitable mixture in air. Diesel sits well above ordinary ambient temperatures. Petrol sits far below them.
That means a diesel tank in an open yard on a hot day is holding a liquid. A petrol tank in the same yard is holding a liquid and continuously producing a vapour that will ignite if it finds a source. Because petrol vapour is heavier than air, it does not disperse upwards and away. It sinks, follows the ground, and collects in pits, trenches, drains and the low corner of a shed, which is how it reaches an ignition source that is nowhere near the tank.
| What differs |
Diesel |
Petrol (ULP) |
| Australian classification |
Combustible liquid |
Flammable liquid |
| Vapour at ambient temperature |
Negligible in normal handling |
Continuous, and heavier than air |
| How far the hazard extends |
Essentially the tank and the fill point |
Wherever the vapour can travel and settle |
| Separation and siting |
Controlled, and usually straightforward |
Controlled more stringently, and often the deciding constraint |
| Ignition source control |
Good practice |
A primary control, extending beyond the tank itself |
| Equipment |
The standard diesel range |
Specified for petrol from the start, not adapted |
Confirm the position before you choose the tank
In Australia the storage and handling of flammable and combustible liquids is addressed by AS 1940, alongside state and territory requirements and local council conditions. What applies to your site depends on the quantity you intend to hold and on the site itself. That is worth establishing early, because it can rule out a location before it rules out a tank, and relocating a proposed petrol installation on paper costs nothing.
What Changes When the Fuel Is Petrol
The hazard
Vapour, not liquid
The thing being controlled is the vapour above the fuel rather than the fuel itself. That is why ventilation, drainage and the low points around a tank matter as much as the tank does.
The site
Separation distances
Distance from boundaries, buildings, openings, drains and other stored materials is treated more stringently than for diesel, and on a constrained site it is usually the first thing that limits where a tank can stand.
The surroundings
Ignition sources
Control extends past the tank to whatever the vapour could reach: electrical fittings, hot work areas, vehicle movements and anything at low level where vapour settles.
The hardware
Petrol-specified equipment
Tank, pump, filtration and dispensing components are specified for unleaded from the outset. Diesel equipment is not converted to petrol duty by changing the label on it.
The Regulatory Position, and What This Article Deliberately Does Not Say
The substantive point above is reliable: petrol is a flammable liquid, diesel is a combustible liquid, and petrol is treated more stringently as a result. Everything that follows from it is site specific, and this article does not put numbers on it.
No separation distances, quantity thresholds, notification or licensing triggers, hazardous zone classifications or standard edition numbers are stated here, because those depend on the quantity, the site, the state or territory and the local council, and because they change. They should come from the current instruments and be confirmed by someone with them in front of them.
The instruments and bodies to work from are AS 1940 for the storage and handling of flammable and combustible liquids, your state or territory work health and safety regulator, your state or territory environment regulator, your dangerous goods regulator where one applies separately, and your local council for planning conditions. A-FLO's existing guides on Australian standards for fuel tanks and on council and EPA approval for above-ground tanks cover the approval pathway in more detail.
What a Petrol Installation Looks Like in Practice
Establish the regulatory position
Quantity and site first, against AS 1940 and the state and local requirements. This determines what is possible before anything is specified or ordered.
Fix the location
Separation from boundaries, buildings, openings and drainage, and an honest look at where vapour would travel if it were released. Low points near the tank are the ones to worry about.
Choose a self-bunded format
A self-bunded tank carries its secondary containment in a second skin, so containment arrives with the tank rather than being built around it. On petrol, where a release is a vapour problem as well as a spill, that matters more than it does on diesel.
Specify the equipment for petrol
Tank, pump kit and filtration together, rated for unleaded. The ULP Systems range is built this way so the compatibility question does not arise.
Size it to turnover
Petrol quality becomes a question when it sits. Size the tank so the fuel cycles regularly rather than sitting for months, which is covered in more detail below.
Plan monitoring and response
Level monitoring so the tank is not opened to check it, spill containment at the dispensing point, and a response procedure people have actually read.
Sizing a Petrol Tank: Let Turnover Decide
On diesel, oversizing a tank is mostly a cost question. On petrol it is a quality question as well, because petrol held for long periods is petrol whose condition becomes uncertain, and the equipment most sites run it in is sensitive to that.
Size the tank so it cycles. A site consuming a few hundred litres a week is generally well served in the 600 to 2,000 litre range, while higher-consumption operations move up through the 3,000 to 8,000 litre capacities. A-FLO's bulk ULP tank range steps through 600, 1,000, 2,000, 3,000, 4,000, 6,000 and 8,000 litres precisely so capacity can follow consumption rather than rounding up to the next convenient size.
Two families cover it. GENCUBE ULP is the self-bunded format, supplied as a complete unit with a 12V ULP pump kit and filtration already matched to the tank. The PETROLBOX family covers on-site petrol holding and dispensing in the same way. There is also a bare ULP Fuelcube for sites that already have compliant dispensing equipment in place.
Filtration is not optional on petrol
Petrol-fuelled equipment, and small engines and generators in particular, is sensitive to particulate and water carried over from the tank. Filtration on the dispensing side protects that equipment, which is why it is supplied as part of the ULP pump kit rather than left as an accessory to remember.
Who Actually Needs Bulk Petrol On Site
Bulk petrol is a smaller market than bulk diesel, and the sites that need it usually know why. Three patterns come up repeatedly.
- Petrol plant and small engines. Pumps, compactors, saws, blowers, mowers and the general run of two-stroke and small four-stroke equipment on a property or a works depot.
- Petrol generators. Standby and prime power units that need fuel available without a trip, which is the case the GENCUBE ULP range is built around.
- Light fleets on remote sites. Petrol vehicles on properties and remote operations where a run to a service station costs half a day of someone's time.
In each case the argument for holding fuel on site is the same as it is for diesel. The difference is only that the installation has more conditions attached to it.
What Goes Wrong
- Choosing the tank before confirming the position. The most common and the most expensive, because the site constraint usually bites after the order.
- Treating a petrol tank as a diesel tank with different contents. The classification is different, so the siting and the equipment are different.
- Repurposing diesel equipment. A pump and filtration package specified for diesel is not made suitable for petrol by putting petrol through it.
- Ignoring low points near the tank. Vapour sinks. A pit, a trench or a drain within reach of the tank is part of the problem even though it is not part of the installation.
- Oversizing. A tank sized for the busiest imaginable month holds petrol for long stretches in every other month.
- Leaving filtration out. The equipment that runs on the fuel is usually less tolerant than the vehicles that run on diesel.
Frequently Asked Questions
Is storing petrol on site treated differently to storing diesel?
Yes, and considerably so. Petrol is classified as a flammable liquid and diesel as a combustible liquid. Petrol produces ignitable vapour at ordinary ambient temperatures and that vapour is heavier than air, so siting, separation distances and ignition source controls are all applied more stringently. The requirements that apply to your site depend on the quantity and the site itself.
What standard covers on-site petrol storage in Australia?
AS 1940, the storage and handling of flammable and combustible liquids, is the principal standard, and it sits alongside state and territory work health and safety and environmental requirements and local council planning conditions. What applies depends on quantity and site, so the position should be confirmed against the current instruments rather than assumed.
Can I use a diesel tank for petrol?
No. Bulk petrol tanks and their pump and filtration equipment are specified for unleaded from the start rather than adapted from diesel equipment. A-FLO supplies petrol storage as a separate ULP range for that reason.
What size petrol tank should I install?
Size it so the fuel cycles rather than sits, because petrol held for long periods raises a quality question. A site using a few hundred litres a week is generally well served by a 600 to 2,000 litre tank, and higher-consumption operations move up through the 3,000 to 8,000 litre capacities.
Why does petrol vapour matter so much?
Because it is heavier than air, so it does not rise and disperse. It sinks, travels along the ground and collects in pits, trenches, drains and low corners, which means it can reach an ignition source some distance from the tank. That is why the controls extend beyond the tank itself.
Should a petrol tank be self bunded?
A self-bunded tank carries its secondary containment in a second skin, so containment arrives with the tank rather than being constructed around it on site. A-FLO supplies bulk ULP storage in self-bunded GENCUBE format from 600 to 8,000 litres.
Do I need filtration on a petrol tank?
Yes. Petrol-fuelled equipment, particularly small engines and generators, is sensitive to particulate and water carried over from the tank. Filtration on the dispensing side is supplied as part of the ULP pump kit rather than left as an optional extra.
What should I sort out first when planning petrol storage?
The regulatory position, before the tank. What applies depends on the quantity and the site, and it can determine where a tank is allowed to stand. Establishing that early is far cheaper than discovering a siting constraint after equipment has been ordered.