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

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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!”

Fortunately "breaching" is an uncommon scenario, however it can happen in areas with heavy rain OR a low water table. This makes it imperative that you use deadmans to secure your tank in place.

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, geography, climate, environmental impact and cost. Most of the time these site specific details are what will end up making the decision for you. This month's blog will outline these different variables to help you make a decision on which type of tank is best suited for your property.

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 them stand out from the steel tank are its anti-corrosive nature and strength-weight ratio. The number one reason why petroleum marketers choose fiberglass for their fuel containment solution is its anti-corrosive nature. Additionally, when considering the overall weight of the product, fiberglass has a relatively strong strength-weight ratio. Both of these characteristics work together to create a great fuel containment solution. 

Xerxes double wall fiberglass fuel underground storage tank petroleum UST

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 fiber-reinforced plastic combined with a matrix like polyester resin. The resulting material has the ability to resist corrosion from unwanted microbes and works together to create a high strength-weight ratio.


Where is your site located? What kind of buildings and roadways surround your site? Are you situated on an intersection or a roadway? 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 replacement or installation 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 need to plan for how your tanks will be positioned underground. An important variable to remember is that fiberglass tanks are oblong in shape and require more real estate to be buried underground whereas steel tanks have flat ends which helps them fit more ergonomically underground for sites with limited real estate.


Fiberglass is a durable material, which has helped make it a choice material amongst fuel marketers operating in harsh climates. Its ability to resist corrosion is unparalleled and has made it the preferred choice for fuel marketers operating in all types of climate conditions. Good choice for humid locations or sites with exposure to salt such as coastal climates or cold snowy conditions.

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. The costs of disposal can be an unexpected expense when it comes time to replace the tank.


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. Generally speaking, fiberglass tanks cost more because of the cost of production. However, as the old adage 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 your fueling equipment.

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 Modern Welding's Glasteel Material. This double wall tank is the most cost effective UST solution on the market. Additionally, steel has superior structural strength and provides complete compatibility with all blends of ethanol and biodiesel fuels.

Modern Welding Glasteel II fuel underground storage tanks

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 equipment. The significant difference between steel and fiberglass is the attributed compressive and tensile strength; steel is higher in both. This gives it a better strength-weight ratio and makes it the ideal choice for fueling stations that need to support heavy equipment.


Again, this is another critical consideration to make when deciding which material to use. Where is your site located? Intersection? Roadway? Traffic thoroughfare? 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. For example, a fuel marketer located in San Francisco might be more privy to installing a steel storage tank because the tank design is more compatible for squeezing into tight spaces (flat end vs. rounded end). However, a fuel station located in Red Bluff is much more likely to purchase a fiberglass tank 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. 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 harsh 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 gaining a return on investment.


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 fact 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 affordable prices 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 from their bed. Depending on your site location, the equipment needed to install a steel tank can potentially outweigh the upfront cost of a fiberglass tank.


When considering tank replacement there are several factors that need to be taken into consideration before purchasing your UST. 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. 

Containment solutions CSI double wall fiberglass underground storage tanks