Bunded vs Non-Bunded Diesel Tanks: What Is the Difference?

When you order a diesel tank, one of the first questions is whether it should be bunded. Here is what that means, and how to choose.

What is a bunded tank?

A bunded tank is a tank inside a second tank. The inner tank holds the fuel. The outer one, called the bund, catches any fuel that leaks, overflows or spills. A common industry rule is that the bund should hold at least 110 percent of the inner tank’s capacity.

A non-bunded tank is a single-skin tank. If it leaks, the fuel goes straight onto the ground, unless the tank sits inside a separate concrete bund wall.

Why bunding matters

• Safety: spilled diesel is a fire risk and a slip hazard.
• Environment: diesel soaks into soil and groundwater, and it is expensive to clean up.
• Less fuel lost: slow leaks are caught and spotted early instead of draining away unnoticed.
• Security: many bunded tanks come with lockable fill points and covers, which makes fuel theft harder.

When a non-bunded tank can make sense

A single-skin tank costs less. It can work where the tank sits inside an existing concrete bund wall, or on a site that already has proper spill containment.

What about double-walled tanks?

A double-walled tank has two steel walls with a small gap between them. It protects against leaks and against damage from outside, and it takes up less space than a tank sitting inside a larger bund.

Which should you choose?

For most factories, estates, hospitals, schools and farms, a bunded or double-walled tank is the safer long-term choice. For large tanks, check the rules that apply to your site with your local authorities and your insurer before you order.

We build self-bunded, non-bunded and double-walled diesel tanks in Lagos. Not sure what size you need? Read how to choose the right diesel tank size, or ask us for a quote.