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Steel Vs. Fiberglass - Two UST Heavyweights Go Head-to-Head in Petroleum Storage


UST breach through driveway after heavy rain saturation underground storage tank.
Recently a customer contacted Shields, Harper asking what kind of material they should use to replace their underground storage tank (UST). Our sales rep for the region asked him, “Well, why do you need to replace your tank?” He responded, “My tank just breached through my driveway! After yesterday’s heavy rain the tank bed filled with water and forced my tank up through the ground!”

Determining your tank solution can be a tough decision. Depending on your site there are a number of different factors that need to be taken into consideration such as material properties, cost, geography, climate and environmental impact. Most of the time these site specific details are what will end up making your decision for you, which is why we’ve written this comparison. By using the following outline you will be able to make an informed decision that best suits your business needs.

Fiberglass Storage Tanks

Fiberglass UST’s have been utilized in the petroleum industry since the 1970’s and over the years have proven to be a great choice for petroleum containment. Some of the characteristics that have helped it stand out from the steel tank are its anti-corrosive nature and good strength-weight ratio. Fiberglass is naturally more anti-corrosive than steel which is the number one reason why petroleum marketers don’t even think twice when it comes to their fuel containment solution. On top of this fiberglass has a relatively strong strength-weight ratio, especially when considering the overall weight of the product. Both of these characteristics add up to create an exceptional product for your fuel containment needs. Keep in mind that these industry leading characteristics merit a higher cost than your average steel tank.

Xerxes Double Wall Fiberglass underground storage tank UST being lowered into ground during tank replacement in Adelanto, CA

Material Properties – Fiberglass

The most attractive quality of a fiberglass UST is its ability to resist corrosion. This is due to the fact that fiberglass is a composite material; a material made up of individual components. It is made of a type of fiber-reinforced plastic where the reinforcement fiber is specifically glass fiber, combined with a plastic matrix like epoxy or polyester resin. The resulting material has the ability to resist corrosion from unwanted microbes and combines to create a high strength-weight ratio.


Cost makes a big difference when it comes to purchasing a tank, which is why it is important to know what you’re buying before you pull the trigger. As mentioned in the material properties section, fiberglass tanks cost more because the product must be constructed from new material each time it is manufactured. As the saying goes, “you get what you pay for” and in this case there is no exception. When properly taken care of a fiberglass tank will outlast the rest of the equipment on your site. So far their reputations speak for themselves.


Where is your site located? What kind of buildings and roadways surround your site? Are you situated in a busy metropolitan area or do you have open space surrounding your property? How much traffic passes by your property? And what is its proximity to the site? These are all important considerations to make when planning the installation or removal of your UST. You will need to account for storage space, equipment space, work space, cost of construction, etc. If you’re situated on a busy intersection with limited real estate, then you will likely have no choice but to do a fiberglass tank replacement. This is because fiberglass tanks are easier to ship, easier to manipulate and easier to lower into the ground. When you have limited space to work with you will want a product that is lightweight and easy to handle.


Similar to steel, fiberglass is also a durable material, which has helped make it a choice material amongst fuel marketers operating in harsh climates. This is where fiberglass stands out. The material’s ability to resist corrosion is unparalleled and has made it the number one choice for fuel marketers operating in all types of climate conditions. Its durability helps it withstand severe weather conditions and other natural phenomena that can disrupt its bed, structure and fittings.

Environmental Impact

More often than not, the long-term environmental impact is overlooked when purchasing UST’s. Fiberglass poses a larger financial burden to the fuel marketer because of the lack of fiberglass recycling infrastructure. Although it can be done, recycling fiberglass is a complicated process and does not yield as much money as steel. This makes the overall decommissioning cost of a fiberglass UST higher than a steel UST.

Steel Storage Tanks

Since 1916 the Steel Tank Institute (STI) has been overseeing the production and installation of steel tanks for the petroleum industry. Their long history of service has led to exceptional steel tank technology, such as the sti-P3®. This cathodically protected double wall tank is the only UST design which allows for on-going monitoring of corrosion protection. Steel has superior structural strength and provides complete compatibility with all blends of ethanol and biodiesel fuels.

Modern Welding double wall underground Storage tank replacement UST

Material Properties - Steel

Steel boasts superior structural strength over any other tank material. This is an attractive quality for areas that undergo severe weather changes or sites that expect to support heavy loads driving over their property. The significant difference between steel and fiberglass is the attributed compressive and tensile strength; steel is higher in both. Having high strength, stiffness, toughness and ductile properties gives it a better strength-weight ratio and makes it the ideal choice for fueling stations that need to support heavy loads, i.e. – truck stops.


Perhaps the most attractive quality of a steel tank is the cost. Just as the price of gasoline fluctuates, so does the price of aggregate steel. Due to the face that steel is sold by the pound, the manufacturer can purchase and produce steel tanks at fair market value. This allows them to sell tanks at relatively affordable prices (compared to fiberglass) and depending on your site needs, make a great solution for storing your product. But be careful, steel tanks typically weigh 4x greater than fiberglass tanks and require heavy equipment to lower and remove them from their bed. Depending on your site location, the equipment needed to install a steel tank can sometimes outweigh the upfront cost of a fiberglass tank.


Again, when deciding on whether to choose a steel or fiberglass tank, it is imperative that you consider your proximity to buildings, roadways and thoroughfares. Answering these questions will help you determine installation costs, what kind of equipment you’ll end up using to install and remove, as well as help you decide how the fuel system will operate. Replacing a steel tank, because of its weight, requires heavy equipment to remove the old tank and lower in the new one. For example, a fuel marketer located in San Francisco is less likely to purchase a steel tank because of the tight parameters that typically surround fuel stations in this area. However, a fuel station located in Red Bluff is much more likely to purchase a steel UST because of the extra room they have available for installation.


What type of climate surrounds your site? When dealing with a steel UST you need to consider the fluctuation in temperature between the winter and summer months, the amount of saturation the ground receives and the humidity levels that are common in your climate. All of these variables will help you determine the best solution for your site. A steel tank, because of its heavier weight, is less likely to breach when the site becomes saturated, however it is more likely to corrode in humid climates. Will your steel tank be able to handle the fluctuation in temperature during the winter months when fittings are more likely to shrink and create leaks? All of these questions need to be answered in order to determine the best solution for your site.

Environmental Impact

Steel is a 100% recyclable material making it environmentally friendly, easier on the wallet and gives you the ability to sell the tank to a metal recycler at the end of its life. This is an attractive quality for tank operators interested in purchasing a sustainable product. Currently tanks are being manufactured with more than 50% recycled steel and end up being recycled at the end of their life by scrap metal recyclers who pay a good prices for the material.


When considering tank replacement there are several factors that need to be taken into consideration before purchasing your underground storage tank. Depending on your site specific needs, you will want to consider your site geography, climate and location. Each factor plays an important role in determining the longevity of the tank life, overall cost of the product and ease of installation.

Whichever decision you make, it is important to remember that in order for the tank to perform at its maximum capability, you must perform routine maintenance to keep the tank operating in optimal condition. This includes tank monitoring, performing leak tests, testing product pH and more. By performing routine maintenance, your tank will continue operating at high performance and ensure that your customers are provided with premium product. 

  Shields, Harper & Co.
4591 Pacheco Blvd.
Martinez, CA 94553

(510) 653-9119
(800) 772-2300
Fax: (510) 658-8448
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