Do You Need a Bunded Oil Tank?

The short answer

You need a bunded oil tank if it holds more than 2,500 litres, or if a risk assessment shows that a leak could pollute nearby water, a borehole or a drain. In practice, most new domestic installations are bunded. A single skin tank is only allowed where an OFTEC registered technician confirms the site is low risk.

What is a bunded oil tank?

A bunded tank is a tank within a tank. The inner tank holds the oil, and the outer tank, the bund, can hold at least 110% of the inner tank’s contents. If the inner tank leaks, the bund catches the oil before it reaches the ground. A single skin tank has just one wall, so any leak goes straight into the soil, drains or water.

When a bunded oil tank is required

Under OFTEC guidance for England, a domestic oil tank normally needs to be bunded if any of the following apply:

• The tank holds more than 2,500 litres
• It is within 10 m of controlled water, such as a river, stream, ditch or pond
• It is within 50 m of a borehole, well or spring
• It is sited where spilled oil could reach a drain or an open or loose-fitting drain cover
• It stands over hard ground where spilled oil could run off into a drain or watercourse
• It supplies a building other than a single-family home
• The vent pipe outlet can’t be seen from the fill point
• The risk assessment identifies any other significant hazard

If none of these apply, a single skin tank may be acceptable. Many homeowners choose a bunded tank anyway because it protects against costly clean-ups.

How the risk assessment works

When a tank is installed or replaced, an OFTEC registered technician assesses the site. They check the tank’s capacity, its distance from water, boreholes and drains, the ground it stands on, and whether the delivery driver can see the vent from the fill point. The result decides whether bunding is needed. The technician also checks the fire siting distances: 1.8 m from non-fire-rated buildings, eaves, openings and flues, and 760 mm from non-fire-rated boundaries. See our OFTEC regulations guide.

Bunded vs single skin oil tanks

Browse our bunded oil tanks and single skin oil tanks.

Why choose a bunded tank even if you don’t have to

Even on a low-risk site, a bunded tank has practical advantages. An oil leak from a single skin tank can soak into the ground under your home or a neighbour’s garden, and the clean-up is often far more expensive than the tank itself. A bund also keeps the valve, filter and gauge under a lockable lid, which helps deter oil theft and protects the fittings from weather. Some insurers and mortgage lenders also look more favourably on a tank that meets current standards.

Bunding for farms and businesses

The 2,500 litre threshold applies to tanks serving a single home. Businesses in England storing more than 200 litres of oil, including diesel and heating oil, generally need secondary containment under the oil storage regulations, and farms storing fuel oil have their own rules. Bunded fuel stations and fuel points meet these requirements in a single unit. See our bunded fuel stations.

Are the rules different in Scotland, Wales and Northern Ireland?

Yes. Scotland, Wales and Northern Ireland have their own oil storage and building regulations, and some apply bunding rules more widely than England. This guide covers England, where we work across Lincolnshire, Nottinghamshire, Yorkshire and Rutland. If you’re elsewhere, ask a local OFTEC registered technician.

Replacing an old single skin tank

Many older homes still have single skin tanks fitted under earlier rules. When yours needs replacing, the new tank is assessed against today’s rules, so you may need to switch to a bunded tank or move it to a new position. We handle the whole job: survey, removal and recycling of the old tank, a new base if needed, and transferring your oil into the new tank. See our oil tank replacement service and guide to oil tank sizes.

Frequently asked questions