Retrofit of Fuel Systems in Existing Buildings


The hazard-resistant design features needed by current codes may be missing from existing buildings. Moreover, the flood threat at the site of the building may have changed after construction — the position of the building may be more vulnerable to flooding or may be prone to higher base flooding. As a result, existing structures are even more vulnerable to flooding. Common flood-related faults of current fuel systems include: 


  • When inundated by floodwater, inadequately anchored fuel tanks can become displaced from their foundations. When removed, tanks or the fill, vent, and fuel lines leading to them are often destroyed, allowing the discharge of fuel that can contaminate the building and surrounding environment.
  • Partially filled fuel tanks can implode when submerged by floodwaters and cause fuel to be released.
  • Fuel tanks with vents not extending above the design flood depth or fuel tanks with non-watertight filling lines may either become contaminated with floodwater when submerged or cause fuel to be released when displaced by floodwaters.
  • Fuel pumps, which are used to transfer fuel oil from main storage tanks to tanks or equipment on elevated floors, can fail when floodwaters inundate. The equipment they support will only work for a limited period when fuel pumps fail before the equipment exhausts the fuel stored on the upper floors.


All components and equipment should either be elevated above the BFE or DFE as defined by ASCE 24, whichever is higher or protected from flooding to that height, to ensure fuel systems remain operational during and after a flood event. Since codes that allow parts of the fuel system to be put at risk of flooding, it may not be feasible to elevate all components of a fuel system, therefore it may be important to protect system components from flooding. The following mitigation steps identify methods for floodproofing of the main elements of a fuel oil system.

Fuel Tanks

For situations where fuel oil tanks can not be elevated, flood protection can be provided by replacing the tank with one that can withstand floods and flood forces or by putting the tank in a dry flood-proofed location.


Tank replacement. Replacing the tank with one that can withstand flood forces offers flood protection by ensuring the fuel tank can withstand the hydrostatic pressures and buoyancy (uplifting) forces for the flood event design. This could involve ensuring that the application of the tank is within the boundary conditions set out in tests performed on it, requirements it complies with, or instructions given by the manufacturer.


  • Hydrostatic pressure can cause imploding of tanks. For example, a tank that extends 10 feet below the level of the flood must withstand pressures as high as 640 pounds per square foot. Also tanks listed for underground applications can not be designed to withstand hydrostatic pressures if they are mounted at greater depths than the manufacturer specifies.


  • The buoyant force on a tank may cause it to break from its base or may push it out of the ground in the case of a buried tank. For example, when submerged, an empty 25,000-gallon fuel oil tank can experience more than 200,000 pounds of buoyant force. Using this example, if concrete ballast was used to stabilize the tank and the ballast was inundated with floodwaters, it would take almost 2,400 cubic feet of concrete (about 14 feet square by 14 feet high) to overcome the buoyant force. The weight of liquid material in a tank balances the buoyant force and decreases lift. Nevertheless, since the amount of fuel in a tank can vary, it is not advisable to depend on the weight of the material within the tank to resist the buoyant forces. Tanks should be properly secured where possible to avoid flotation when the tank is completely empty. If the amount of anchorage needed is not necessary, anchorage should be adequate to prevent the tank from floating when it contains the least amount of fuel oil it will usually hold. Anchorage points will be spread around the tank to prevent the tank from experiencing disproportionate uplift forces.


Dry floodproof. Providing protection by dry floodproofing means placing the tank in a watertight space. Tanks that can not withstand hydrostatic pressures or which can not be anchored to withstand floating can be put in reinforced rooms built to withstand hydrostatic pressures and anchored to prevent flotation. The spaces, also called vaults, are usually made of reinforced concrete because its density helps offset the buoyancy, and concrete can withstand hydrostatic pressures with proper reinforcement. Also useable are steel vaults, which are usually lighter than concrete, but also require additional mass or anchorage to withstand buoyant forces.

Because rooms that contain tanks need access and ventilation to prevent the explosive concentration of gases from accumulating, they should be fitted with specially built, watertight submarine doors and ventilation equipment that vents above the level of flood size. Also, even if dry floodproofing means rendering a building or area “substantially impermeable” inside a house, meaning that no more than 4 inches of water depth may accumulate over a 24-hour span, some water can accumulate so that an internal drainage collection system is needed. It’s recommended to use sump pumps supplied by emergency power sources.


Fuel Pumps

Fuel pumps should also be protected from floodwaters and their controls. Two general types of pumps exist submersible pumps, and external pumps. Submersible pumps that are installed inside the fuel tank are typically used in underground tanks, and sometimes in building tanks above ground. External fuel pumps are usually not floodwater tolerant and can only be used if they are installed in dry floodproof areas. For both types of pumps the pump controls and power should be elevated, dry floodproofed, or designed for submerged operation.


Fill Lines and Tank Vents

All filling lines, pipes, and connections should include suitable components ( i.e. valves) to prevent floodwaters from contaminating fuel tanks and to prevent fuel from escaping during a flood. Tank vents should also be either extended above flood levels or provided with inspection valves that prevent floodwaters from entering the vents when they are submerged. Since a check valve failure can lead to contaminated fuel, it is preferable to extend the vent lines above the DFE. Those guidelines comply with the specifications of NFPA 30.

Contact the Premier Source for Remote Fill Systems

Remote Fill Systems is the premier source for remote fill tanks and systems for generator fueling. We are committed to providing knowledgeable and experienced support to our customers from design and application through startup and commissioning. Our team has many years of experience with fuel oil as well as long experience in industrial process control and mechanical HVAC and piping systems. We have developed innovative and cost-effective products in response to customer needs, such as:


Concealment of the Remote Fill — Architects want to retain the appearance of their designs. The Concealed Underground Remote Fill allows the appearance and beauty of a building to be undisturbed. The Concealed Underground Remote Fill provides a code compliance solution where the required clearance to building openings cannot be achieved with an above ground product.