Thoughts And Perspectives From The Team

Single Wall vs. Double Wall Fuel Tanks

AUTHOR T Bailey, Inc.

PUBLISHED Nov 13, 2022

There are several different types of fuel storage tanks and choosing the right one can be daunting. However, the first step is to undertake a comparison between single wall vs. double wall fuel tanks.

Safety is the key issue when it comes to fuel storage. It’s essential to protect both people and the environment from the possible dangers of toxic and highly combustible substances. Besides being safe, your tank should be cost-effective, functional, and durable.

T BAILEY, INC is a leading fabricator of all types of tanks for storing all manner of substances, from hazardous chemicals to water. We have compiled this handy guide to help you specifically select the fuel tank that best suits your needs.

The Difference Between Single Wall and Double Wall Fuel Tanks

Single wall tanks only have one shell encasing the fuel, whereas double wall tanks have an inner shell surrounded by a second, larger containment shell.

Every fuel tank requires secondary containment that will prevent fuel from entering the environment. For a single wall tank, this safety feature has to be built into the storage site, as it’s not present in the tank itself. This is called external bunding. Specialist civil engineering is necessary for this construction.

A double wall tank has an interstitial space between the two walls that fulfills the function of secondary containment in the event of leakage. No external containment safety feature is required in the storage site. For this reason, a double wall tank is referred to as a self bunded tank—essentially it’s a tank within a tank.

In terms of storage, double wall tanks are safer than single wall tanks, and also suitable for the transportation of fuel.

Advantages of Single Wall Tanks

To comply with the Environmental Protection Agency’s (EPA) Spill Prevention, Control, and Countermeasure Plan (SPCC), single wall tanks require an epoxy-coated concrete dike for secondary containment. (Exceptions are diked tanks that have built-in integral steel dikes.)

If you have a concrete dike, then a single wall tank offers the following benefits:

  • Affordability: Single wall tanks are substantially cheaper than double wall tanks—they cost about a third of the price.
  • Convenience: They have a smaller volume and footprint than double wall tanks of the same capacity.
  • Flexibility: Some single wall tanks can be divided into compartments to accommodate different fuel products.
  • Weather Resistance: Advanced coating systems can be added to outdoor tanks to protect against the elements. 

Advantages of Double Wall Fuel Tanks

Double wall fuel tanks are more expensive but offer several advantages. This type of tank will be your safest and most reliable choice, due to:

  • Automatic EPA compliance: Your tank meets the EPA requirement for secondary containment provided that:
    1. It is shop-fabricated.
    2. The inner tank is a Underwriter Laboratories (UL)-listed steel tank.
    3. It has an overfill alarm and flow shut-off.

(Note that tanks that are double-walled for fire rating purposes have insulation in the interstitial space and therefore may not be EPA compliant in terms of secondary containment.)

  • Leak monitoring: A sensor monitors the vacuum between the shells. Loss of vacuum indicates a leak.
  • Weather resistance: The outer wall protects the contents from weather conditions. In addition, specialized exterior coatings can add extra protection.
  • Purposes: They are very versatile and have a wide range of applications.

Uses and Designs of Double Wall Fuel Tanks

Double wall fuel storage tanks can be any size, vertical or horizontal, aboveground or underground. They can hold diesel, gasoline, kerosene, etc.

T BAILEY offers several options: 

1. Fireguard® Tank: Insulation between the walls protects fuel from ambient temperature variations, and exceeds the UL 2-hour fire test.

2. Flameshield® Tank: Registered Steel Tank Institute tank with a 2-hour 2,000 fire rating for fire resistance.

3. Contain-A-Tank: A cylindrical primary tank and integrated rectangular outer tank are SPCC compliant for secondary containment.

4. UL142/F921 Tank: Registered Steel Tank Institute tank that meets UL142 Standard for Steel Aboveground Tanks for Flammable and Combustible liquids.

Single Wall vs. Double Wall – Which Should I Get?

Consider getting a single wall tank if:

  • You have a tight budget and a pre-existing secondary containment area.
  • You have limited space and need a smaller tank.
  • You require a compartmentalized tank for storing different products.
  • You’re in a jurisdiction that isn’t subject to EPA’s SPCC regulations. (Check your local applicable legislation.)

Consider getting a double-wall fuel tank if:

  • You don’t have a secondary containment area, or the space to build one.
  • You want a hassle-free way to comply with EPA's SPCC regulations. 
  • You want a durable outdoor tank that can resist adverse weather conditions.
  • You want to reduce the chance of leaks occurring if the tank gets damaged.
  • You want an externally visible vacuum gauge that can detect leaks.


Now that you’ve considered your unique situation and weighed up single wall versus double wall fuel tanks, you’ll want to partner with a company that specializes in fabricating all manner of tanks. T BAILEY will specifically engineer your tank to meet your requirements, ensure compliance, and withstand any environmental conditions. 

Whether your tank is small or enormous, our heavy steel fabrication shop can make it and our coatings division can prepare it to store any fuel product. Call us today!