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When it comes to storing diesel safely and efficiently, choosing the right type of fuel tank is essential. The two most common options are single-skin tanks and self-bunded tanks. While they might look similar from the outside, there are important differences between them — especially when it comes to compliance, safety, and environmental protection.

In this guide, we’ll break down what each type of tank is, how they work, and which option is best for your needs.

1. What is a Single-Skin Diesel Tank?

A single-skin diesel tank has just one layer of steel or poly construction between the fuel and the outside environment.

Key characteristics:

• One wall of containment – no built-in spill protection.
• Typically used for smaller, temporary setups or where additional external bunding is in place.
• Requires the installation of a separate bund wall or spill containment system to comply with environmental regulations.
• Lower upfront cost compared to self-bunded tanks.
• When single-skin tanks are used:
• Farms or sites with dedicated concrete bund areas or spill pallets.
• Environments where mobility and lightweight construction are priorities.
• Operations with strict internal spill management systems.

Important: Under Australian Standard AS 1940, a single-skin tank cannot be used on its own for long-term diesel storage unless it sits inside a compliant bunded area that can contain at least 110% of the tank’s capacity.

2. What is a Self-Bunded Diesel Tank?

A self-bunded diesel tank — often called a double-wall tank — has two layers of steel or poly construction, with a sealed space (the “bund”) between the inner and outer walls.

This design acts as built-in spill containment, meaning that if the inner tank leaks, the outer wall catches the fuel before it escapes.

Key characteristics:

• Two layers of protection – inner tank for fuel, outer tank as secondary containment.
• Built-in bund area equals at least 110% of the inner tank’s volume, meeting environmental compliance without additional infrastructure.
• Designed for permanent or semi-permanent installations.
• Available in capacities from small portable units (e.g., 450L) to large stationary bulk tanks (e.g., 100,000L+).
• Often comes pre-fitted with pumps, hose reels, meters, and filtration systems.

Advantages of self-bunded tanks:

• No need to construct a separate bund wall or spill area.
• Easier to transport and relocate as a single, contained unit.
• Reduced risk of environmental contamination and clean-up costs.
• Quicker installation and set-up — simply place, connect, and fill.

3. Compliance and Environmental Requirements

In Australia, diesel storage must comply with AS 1940 – The Storage and Handling of Flammable and Combustible Liquids.
Key requirements include:

• Secondary containment (bunding) must hold 110% of the largest tank’s volume.
• Tanks must be constructed from approved materials (e.g., AS/NZS 4766 for poly, AS 1692 for steel).
• Spill management systems must be in place to prevent soil and groundwater contamination.

Practical difference:

• Single-skin tanks require extra infrastructure like a concrete bund wall or spill pallet to comply.
• Self-bunded tanks meet the standard automatically thanks to their double-wall design.

4. Cost Considerations

While self-bunded tanks have a higher purchase price, they often save money overall by eliminating the need for separate bunding construction and reducing environmental risk.

5. Which Tank is Right for You?

Your choice comes down to application, compliance, and long-term strategy:

Choose a single-skin tank if:

• You already have a compliant bunded area or spill containment system.
• You need a low-cost, lightweight solution for smaller or mobile setups.
• You have strict spill management protocols in place.

Choose a self-bunded tank if:

• You need a plug-and-play solution with built-in compliance.
• You want to minimise environmental risk and future-proof your operations.
• Your site doesn’t have space or budget for separate bunding infrastructure.
• You plan to relocate or expand fuel storage in the future.

Both single-skin and self-bunded diesel tanks have their place, but the trend in Australia is strongly toward self-bunded tanks. Their built-in compliance, safety, and mobility make them the preferred choice for most businesses — from farms and construction companies to industrial fleets.

Before making a purchase, always:

• Check local environmental and council regulations.
• Ensure the tank complies with AS 1940 and relevant Australian Standards.
• Consider long-term operational costs, not just upfront price.
• By understanding the differences, you can make an informed decision that keeps your fuel secure, your site compliant, and your business running smoothly.