Preventing Flotation of Underground Storage Tanks

underground storage tank flotation

Here, deadman anchors are used to hold down these underground storage tanks

The idea of an underground storage tank floating seems counter-intuitive at first. How can a tank float if it’s underground? The answer has to do with buoyancy. Think of a half-filled water bottle. If you toss it into a body of water, it floats, because the air in the bottle exerts an upward force known as buoyancy. The same concept applies to underground storage tanks. If the water table reaches a high level or if flood waters reach a high flood stage, the air in the tank will start to exert an upward force. Because of the large volume of underground storage tanks, this upward force can be very strong. It can even cause the tank to break through the earth above it, and all of a sudden you’ve got an aboveground tank when you wanted an underground tank.

Fortunately, there are several effective methods that will keep a storage tank underground.


  • Increased burial depth- By increasing the burial depth of the tank, you generate more downward force (by means of the weight of backfill), which counteracts the upward force of buoyancy.
  • Deadman anchors- If the burial depth can’t be increased, deadman anchors can be used to anchor a tank down. Deadman anchors are made of reinforced concrete, and help provide additional stability and counteraction against buoyancy.
  • Using a thicker grade paving slab- Concrete grade paving slabs are placed on the surface of the earth above the tank. Because concrete is heavier than earth, a thicker paving slab will exert more downward force on the tank.
  • Bottom holddown slab- This is essentially a paving slab that sits below the underground tank. The tank is anchored to the slab, which exerts a downward force to offset buoyancy. It also provides more stability for the tank.


A quick breakdown of our company:Tanks Logo - 20 Years of First Choice Service

-Nationwide supplier of storage tanks and vessels for 20 years.

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-Distributor for over 55 storage tank and related accessory manufacturers.

-Industry leader since 1993.

As a distributor and installer, we know everything there is to know about the business, which allows us to offer the best quality tanks and proper installation services. Our dual role also makes our services more cost-efficient, and allows you to cut out the hassle of working with independent distributors and installers.

Our status as a national distributor for over 55 storage tank and related accessory manufacturers means we offer a wide variety of tank solutions that are guaranteed to fit your needs, and our emphasis on customer service makes us one of the leading distributors in the industry. We’re focused on providing the best products and services to the consumer in order to remain one of the industry leaders.

We strive for complete customer satisfaction, and with our 20 years of experience, we think you’ll notice the difference you get with us. Let Tanks Direct be your first choice for all of your tank and storage system needs.




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