Double-wall steel tank

F921® aboveground storage tanks are manufactured with a double‐wall steel design. Standard features include built‐in, testable, interstitial monitoring capability and impermeable secondary containment. The F921® delivers uncompromising performance, reliability, service and economy.

F921® Features

  • Meets UL 142, Standard for Steel Aboveground Tanks for Flammable and Combustible Liquids
  • Double‐wall design offers integral, impermeable secondary containment to meet EPA SPCC requirements
  • Primary and secondary tank can be tightness tested on site with standard testing procedures, or manufacturer may ship with vacuum in the interstice to prove integrity of both walls during installation
  • Interstitial space can be monitored for leak detection
  • Primary storage tank and secondary containment compatible with a wide range of fuels and chemicals
  • Support designs available for all seismic requirements
  • Choose from many integral support types, including saddles and skids
  • Vertical tanks supported on legs, and skirted available, with listing label
  • Capacities range up to 75,000 gallons

F921® Benefits

Steel construction allows for recycling
Low cost compartments and customization
Built to nationally‐recognized STI standards with strict third‐party quality control inspection program


F921® is available from an extensive group of Steel Tank Institute fabricators who participate in the STI Quality Control Program. Under the program, independent quality control inspectors make unannounced visits to STI members, ensuring fabrication to the highest possible standards.


  • Aboveground
  • F921
  • Tank Technologies