Do Steel Oil Tanks Need To Be Bunded?

Approximately 1.5 million households in the UK heat their homes with oil, kept in a storage tank outside the house. For many years these tanks were simple, single-skinned fabrications, made from welded steel sheets. But they had a tendency to leak as thermal expansion and contraction and the pressure of a full tank of oil placed strain on the welded joints, while corrosion ate through the steel.

A leaking oil tank is a financial and environmental liability, and when heating oil started to contaminate land and watercourses, it was time to put a stop to it. Oil pollution can be contained if the tank is placed in a secondary containment system such as a sealed tray or pit, called a bund.

From single-skinned to bunded

The problem with an external bund like this is that the bunds were often made of materials that were prone to splitting or cracking, with the result that the oil still escaped into the soil, and from there into watercourses. This solution also failed to do anything to protect the oil tank against damage or corrosion. A better solution was plainly required.

Steel Bunded Oil Tank Cross SectionThus came about the development of the bunded oil tank. Essentially a ‘tank within a tank’, this concept features an inner tank that contains the oil and an outer tank that acts as an integral bund. The space between the inner and outer tank walls is sufficient to contain a greater volume of oil than that of the inner tank. So that if the inner tank fails for any reason, its contents will be safely retained by the outer wall and in the bund.

The outer tank also serves two other purposes, shielding the inner tank from weather conditions that accelerate corrosion and acting as a first line of defence in the event of an accidental impact.

 


Does this apply to all oil storage tanks?

In some parts of the United Kingdom, namely Scotland, Wales and the Channel Islands, all oil storage tanks must be bunded, while in other regions they only need to be bunded if their storage capacity exceeds a maximum volume. This also varies between tanks for domestic use and those for commercial use.

In England, commercial-use oil tanks holding 200 litres or more must be bunded, while domestic oil tanks only need to be bunded if their capacity is 2,500 litres or more. However, this doesn’t mean that smaller-capacity tanks are exempt – if a smaller tank is situated near an open drain or loose-fitting manhole, within ten metres of a watercourse such as a stream or river, within fifty metres of a borehole, well or natural spring, or on hard ground where it could run into a river or stream, it must be bunded. A tank of any size must also be bunded if it serves any building other than a single-family dwelling, if the tank vent isn’t within line of sight of the tank fill point, or if other hazards are present on the site. For a more detailed explanation of the regulations, OFTEC has published a handy information guide.

Do I need to replace my old oil tank with a bunded one?

if you are replacing your old tank and its capacity exceeds the legal maximum, it must be replaced with a bunded tank. Tank replacement will be necessary if, say, your old tank is showing signs of deterioration. In this case, upgrading to a new steel bunded oil tank is sensible. You will benefit by:

  • Removing the risk of losing oil
  • Avoiding the contamination of your immediate environment and of nearby communities; and
  • Avoiding the risk of incurring a financial penalty for any heating oil spilling from a ruptured tank

Even if your oil tank is small enough to be exempt, we would recommend choosing a bunded one for your next tank. This is because it will not only assure you of knowing your oil supply is secure and the new tank will last longer, but it will also protect you in the event of new legislation tightening up on the regulations and banning all single-skinned tanks. Remember that in Wales and Scotland and Wales single skinned tanks are already outlawed.

If you do need to replace your oil for a bunded model, Atlantis Tanks is well-placed to help you. We have no less than 27 steel bunded oil tanks of various capacities from which you can choose. They are manufactured in-house to our own designs for maximum efficiency and longevity.

What other regulations or factors should I consider?

If you are replacing or installing an oil tank, there are a few other points you should bear in mind.

Where you position the tank

For fire security reasons, an oil tank must be situated at least 1.8 metres away from a building, including the overlap of the eaves, unless it is rated for thirty-minute fire resistance, and at least 760 mm from any boundary. The tank should also not be surrounded by any concealing enclosure such as a fence, wall or hedge that isn’t fire-rated.

If there is insufficient space to allow this fire gap between the tank and the building, a thirty-minute fire-rated wall that extends at least 300 mm beyond and above the extent of the tank can be built between them to serve as a fire break. Atlantis Tanks is known for supplying great quality fire-resistant wall sets.  

If the tank capacity is greater than 3,500 litres, you should contact OFTEC or your local Building Control Officer for advice.

A suitable oil tank base

We have talked about tank bases in some detail in our separate article here:
https://atlantistanks.co.uk/oil-storage-tank-base-requirements/

In essence, your oil tank must be placed on a properly constructed base. This should be made of non-combustible materials such as concrete, brick and stone and should extend at least 300 mm beyond the sides of the tank.

Needless to say, with the total weight of a full tank, the base must be strong, stable and protected against ground movement. It should also support the entire base of the tank evenly to avoid localised stress on the tank.

DIY tank installation

While you may be an expert and confident DIY enthusiast, there are good reasons for not trying the installation yourself. In most instances, an insurance company will require an OFTEC certificate for the installation, which can only be provided by an OFTEC-approved installer.

Not having an OFTEC certificate to cover the installation will also have repercussions when you come to sell the property, as a non-certificated installation is likely to reduce the value of the property and even make it harder to sell.

Building Regulations

All new and replacement oil tank installations will require Building Regulations approval, as these will cover its position, base, bund and fire protection.

Building Regulations approval can be obtained from your local Building Control office, but if the work is carried out by an installer registered with a Competent Person Scheme (such as OFTEC in England and Wales) they will be authorised to self-certify their work rather than directly involving Building Control – another benefit of using an OFTEC-approved installer.