Bunded oil tank replacement

A bunded tank is a tank inside a tank. If the inner one splits or a fitting weeps, the outer skin holds the oil instead of the soil. Swapping an old single-skin tank for a bunded one is the most common oil tank job in the country.

For a typical home it costs £1,900 to £2,900 for plastic or £2,600 to £3,800 for steel, with the old tank taken away.

1,200 litre bunded tank, fitted£1,900 to £2,900a guide, not a quote

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Reasons to go bunded

  • Your tank holds more than 2,500 litres, where a bund is required by law.
  • Spilled oil could reach a drain, ditch, stream or pond within 10 metres, or a well, spring or borehole within 50 metres.
  • The vent pipe cannot be seen from where the tanker fills.
  • Your insurer or oil supplier has raised the condition of a single-skin tank.
  • You simply want the protection: OFTEC recommends a bunded tank for homes as a matter of course.

Bunded tank prices

1,000 to 1,250 litres
Plastic / steel		£1,900 to £2,900 / £2,600 to £3,800
1,300 to 1,500 litres
Plastic / steel		£2,200 to £3,200 / £2,900 to £4,200
1,800 to 2,000 litres
Plastic / steel		£2,600 to £3,700 / £3,300 to £4,700
2,500 litres
Plastic / steel		£3,000 to £4,500 / £3,800 to £5,500
How we got these figures

The figures above are our own bands, drawn from three UK cost guides dated 2024 to 2026 and checked in November 2026. They describe the country as a whole rather than your county, and the guides leave VAT unclear, so when quotes arrive check whether each one adds it. Budget with them; the installer's written price is the one that counts.

Work out your price in the cost estimator

What a bund does, and what it does not

The rules describe a bund as secondary containment able to hold at least 110% of the tank's capacity, impermeable to oil and water. On a modern domestic tank the bund is built in: a moulded or welded outer tank around the inner one, with a lid that keeps rain out so the bund stays empty and ready.

A bund protects against slow leaks and splits in the inner tank. It does not protect against everything. Oil can still escape from the supply pipe, from an overfilled tank where the vent is blocked, or from a fitting outside the bund. That is why the pipework, the fire valve and the gauge matter as much as the tank.

Twin-wall is not the same thing

Some older tanks were sold as "twin-walled" or "double-skinned". Council guidance on domestic oil storage is clear that these do not contain spills the way an integrally bunded tank does. If your tank is described that way and you are near water, treat it as single skin when deciding whether to replace.

Old masonry bunds

Many steel tanks from the 1980s and 1990s stand inside brick or block bund walls. Those walls crack, lose their render and fill with rainwater, which means they no longer hold anything. Replacing the whole arrangement with an integrally bunded tank is usually cheaper than rebuilding the wall, and it frees up space.

Choosing the size

Size by your yearly use, not the old tank. A home using around 2,000 to 2,500 litres a year is usually well served by 1,200 to 1,400 litres, filled twice a year. Bigger tanks let you buy in summer when oil is often cheaper, but remember that 2,500 litres is the most a domestic tank can hold before a bund becomes compulsory regardless of position, and 3,500 litres is the ceiling for the household rules altogether. See oil tank replacement prices by size, or the cost estimator.

Swapping a single-skin tank? Tell us the size and we will find an installer for your area.

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From single skin to bunded

A like-for-like swap is a one-day job for most homes.

  1. Measure and check

    The installer checks the base size the new tank needs and the distances from the house and boundary.

  2. Drain the old tank

    Good oil is held in a bowser; sludge and water go for disposal.

  3. Swap

    Old tank cut up and removed, base adjusted, new bunded tank set level and connected.

  4. Refill and certify

    Oil returned, boiler checked, certificate and spill label handed over.

Bunded oil tank questions

Is a bunded oil tank a legal requirement?

For domestic tanks, only where the risk conditions apply: over 2,500 litres, near water, drains or a drinking water source, or where the vent cannot be seen from the fill point. Many installers will only fit bunded tanks now.

How much more does a bunded tank cost than single skin?

Published guides put it at roughly 30 to 50% more for the tank itself. Fitted, the gap is smaller because labour and removal cost the same.

Can I keep my single-skin tank?

If it is sound and none of the conditions apply, yes. Have it checked once a year, and replace it once it shows the signs on our homepage or reaches about 20 years.

What size bunded tank do I need?

Most three and four bedroom homes use 1,200 to 1,400 litres. Larger houses, homes with range cookers and farms often go for 1,800 to 2,500 litres.

Does rainwater collect in the bund?

It should not. Integrally bunded tanks have a covered bund. If you find water in yours, ask an installer to check the lid seals and the bund alarm, if fitted.

Plastic or steel for a bunded tank?

Plastic suits most homes and needs almost no upkeep. Steel suits large sizes, farms and exposed sites, and needs repainting.

Related tank guides

Get a quote for a bunded tank

Three steps: the postcode, the tank, and how to reach you. It takes a couple of minutes at most.

We are a free introduction service, not an installer. We find an OFTEC-registered tank installer who covers your postcode and tell you their name; that firm only hears from us once you give the go-ahead.

Step 1 of 3

Where is the tank?
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