Is a Single-Skin or Bunded Tank Better? An Honest Comparison

Choosing the right oil or fuel storage tank is an important decision for homeowners, farmers, business operators, and anyone who needs to store heating oil or diesel safely. One of the most common questions people face is whether to opt for a single-skin tank or a bunded tank. Both options have their advantages, but they serve different needs—and the right choice depends on your application, budget, environmental considerations, and local regulations.

This article offers an honest, comprehensive comparison of single-skin and bunded tanks, explaining their differences, pros and cons, regulations, and the kinds of situations each is best suited for. Whether you're considering a new installation or upgrading your existing system, this guide will help you make a well-informed decision.

What Is a Single-Skin Tank?

A single-skin tank consists of just one layer of material and is the most basic type of oil or diesel storage tank. These are typically made from plastic or steel and are commonly used in domestic applications for storing heating oil.

Pros of Single-Skin Tanks:

• Lower cost: Single-skin tanks are more affordable upfront than bunded alternatives.

• Lightweight (for plastic models): Easy to handle and install.

• Simple design: Fewer components mean lower maintenance.

Cons of Single-Skin Tanks:

• No secondary containment: If the tank leaks, oil can escape directly into the environment.

• Higher environmental risk: Any leak can lead to soil and water contamination.

• Not always compliant: In many jurisdictions, single-skin tanks are no longer approved for installations above a certain size or in sensitive areas.

What Is a Bunded Tank?

A bunded tank consists of two layers: an inner tank that holds the oil or diesel, and an outer tank (called a bund) that acts as a second containment barrier. If the inner tank leaks or overflows, the outer tank captures the spill, preventing environmental damage.

The term "double bunded oil tank" is sometimes used to refer to bunded tanks that offer even more advanced protection, though this typically means the same as a standard bunded model.

Pros of Bunded Tanks:

• Built-in spill protection: The outer layer provides a safeguard against leaks.

• Regulatory compliance: Required by law in many areas for certain capacities or locations.

• Long-term cost efficiency: May reduce the likelihood of costly clean-up and fines.

• Added features: Bunded tanks often come with integrated gauges, alarms, and locks.

Cons of Bunded Tanks:

• Higher initial cost: More expensive to purchase and install.

• Heavier and bulkier: Requires more space and professional installation.

• Maintenance of both skins: Periodic inspections of both inner and outer tanks are essential.

Key Differences Between Single-Skin and Bunded Tanks

Feature	Single-Skin Tank	Bunded Tank
Layers	One	Two (inner and outer)
Cost	Lower	Higher
Environmental Protection	Low	High
Compliance	Limited	Widely compliant
Leak Safety	Direct leakage	Leak containment
Ideal For	Low-risk domestic use	High-risk or commercial use

When to Choose a Single-Skin Tank

Although bunded tanks are increasingly recommended, single-skin tanks still have their place—primarily in domestic settings where the risk of leakage is low and local regulations permit their use.

Best suited for:

• Homes using low volumes of heating oil.

• Installations where risk to watercourses or drains is minimal.

• Areas with low environmental sensitivity.

• Applications where budgets are tight, and compliance allows.

However, even in these scenarios, it’s critical to conduct regular inspections and consider installing a drip tray or external bund if you opt for a single-skin tank.

When to Choose a Bunded Tank

Bunded tanks are widely considered the safest and most responsible option for storing oil or diesel fuel. If you store large volumes of oil or are close to a watercourse, bunded tanks offer essential protection against environmental harm and legal liability.

Best suited for:

• Commercial and agricultural use.

• Properties near streams, wells, or drainage systems.

• Urban settings where spills could affect multiple parties.

• Installations that store over 2,500 litres.

• Environments where heating oil tank bunded systems are mandated by law.

For example, many industrial users rely on bunded diesel tanks to protect fuel storage operations from leakage while meeting health and safety standards.

Understanding Legal Requirements

In the UK and much of the EU, oil tanks double skin or bunded tanks are legally required for certain storage situations. These include:

• Tanks over a specified capacity (often 2,500 litres).

• Tanks within 10 meters of a river or stream.

• Tanks within 50 meters of a well, borehole, or spring.

• Commercial, industrial, and agricultural applications.

Failure to comply can result in significant fines and environmental penalties. Therefore, even if a single-skin tank seems adequate for your needs, bunded tanks are a smarter long-term investment when compliance is a concern.

Costs and Long-Term Value

Upfront Costs:

• Single-skin tanks are typically 20–40% cheaper than bunded tanks of the same size.

Long-Term Costs:

• Single-skin tanks have a shorter lifespan and a higher risk of environmental liability.

• Bunded tanks may last longer and reduce the risk of oil loss or contamination.

When factoring in the cost of environmental cleanup, insurance claims, or system replacement, bunded heating oil tanks are often the more cost-effective solution over a 10–15-year period.

Installation and Space Considerations

Single-Skin Tanks:

• Easier to transport and install.

• Suitable for smaller spaces.

• May not require professional installation in all cases.

Bunded Tanks:

• Require more space due to their double-wall design.

• Often need to be installed on a solid base and away from heat sources or flammable materials.

• Professional installation recommended or required.

Proper tank positioning is essential for both types. Ensure your tank is:

• On level, stable ground.

• Accessible for delivery and maintenance.

• Away from water sources, trees, and buildings (as per local regulations).

Maintenance Requirements

Both single-skin and bunded tanks benefit from regular maintenance:

• Annual inspections: Look for signs of cracking, rust, or fuel leaks.

• Check gauges and fittings: Ensure all seals are intact and working.

• Monitor fuel levels: Sudden drops may indicate a leak.

• Bund inspections (for bunded tanks): Ensure the bund hasn’t accumulated water, debris, or oil, which could indicate a leak in the inner tank.

A double bunded oil tank may come with extra monitoring features to simplify maintenance.

Future-Proofing and Insurance Considerations

Insurance providers are increasingly favouring bunded tanks due to the reduced risk of claims. Some may even refuse to cover losses from single-skin tanks or offer reduced premiums for bunded alternatives.

Additionally, as regulations evolve and environmental standards tighten, bunded tanks are becoming the norm. Choosing a bunded tank today helps future-proof your investment, avoiding costly upgrades later.

Conclusion: Which Tank Is Better?

There’s no universal answer—but here’s a summary to guide your decision:

• Choose a single-skin tank if:

  • You’re storing a small volume of oil.

  • You live in a low-risk area with no watercourses nearby.

  • Local regulations allow it.

  • Budget is your main concern.

• Choose a bunded tank if:

  • You’re storing over 2,500 litres.

  • Your site is environmentally sensitive.

  • You want long-term peace of mind.

  • You require compliance for business or agricultural use.

While bunded tanks have a higher upfront cost, they offer superior safety, compliance, and value over time. Whether it’s for your home’s heating supply or your business’s fuel management, a bunded diesel tank or bunded heating oil tank is a smart investment for the future.

When it comes to storing fuel safely and responsibly, the best choice is not just about price—it’s about protection, performance, and peace of mind.