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Watco Permatank Outside

STI PERMATANK®

A double-wall jacketed underground storage tank featuring a steel inner tank and corrosion-resistant outer coating — engineered for strength, safety, and longevity.

Built the Watco Way

NextGen Performance and Proven Reliability

STI's NextGen Permatank® is a double-wall jacketed underground storage tank with a steel inner tank and a corrosion-resistant exterior coating that delivers long-term structural integrity and environmental protection.

The latest design features 14-gauge steel, replacing previous standoff materials to create a tight interstitial space for superior performance and EPA-compliant monitoring. Backed by STICO Mutual’s 30-year limited warranty, the Permatank® offers lasting reliability and peace of mind — engineered for today’s most demanding underground storage applications.

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Engineered for Performance and Compliance

Watco Tanks Key Technical Advantages

Design Efficiency
Reduces length to maximize storage without sacrificing real estate, designed shorter than fiberglass tanks of the same capacity, reducing installation costs and increasing layout flexibility
Durability
14-gauge steel replaces previous standoff material, creating a tight interstitial space. Braced double bulkheads provide dual sealed protection between contained liquids and are reinforced with vertical bracing for superior structural integrity
Fuel Compatibility
Steel construction ensures compatibility with all hydrocarbons and can be lined for DEF and JetA/AV Gas applications
Ease of Install
No anchoring required. Optional Watco-manufactured deadman and anchoring packages available for convenience.
Sustainability
100% recyclable steel supports environmental goals and responsible infrastructure design
Built-in Safety
Features a durable non-slip grip with OSHA-level strength for superior safety during installation
Capacity Range
Available in double-wall construction with capacities up to 40,000 gallons, providing scalable solutions for diverse storage needs

Permatank® Design Specifications

Standard Dimensions and Tank Capacities

Diameter Capacity Length +/- 2" Weight +/- 5%
96" 8,000 gal 21'-9" 11,000 lbs
96" 10,000 gal 27'-2" 13,000 lbs
96" 12,000 gal 32'-7" 15,000 lbs
96" 15,000 gal 40'-8" 18,000 lbs
96" 20,000 gal 54'-5" 27,000 lbs
120" 7,000 gal 17'-4" 12,000 lbs
120" 10,000 gal 20'-10" 13,000 lbs
120" 12,000 gal 26'-0" 16,000 lbs
120" 15,000 gal 30'-8" 18,000 lbs
120" 24,000 gal 41'-8" 27,000 lbs
120" 26,000 gal 45'-2" 29,000 lbs
120" 30,000 gal 52'-1" 33,000 lbs
120" 32,000 gal 55'-7" 35,000 lbs
126" 30,000 gal 46'-9" 34,000 lbs
126" 32,000 gal 49'-11" 34,000 lbs
126" 34,000 gal 53'-0" 36,000 lbs
138" 36,000 gal 56'-7" 37,000 lbs
138" 35,000 gal 45'-6" 35,000 lbs
138" 38,000 gal 48'-5" 36,000 lbs
138" 40,000 gal 51'-0" 39,000 lbs

Additional Features:

  • Designed shorter than corrosion-resistant material
    tanks of the same capacity, reducing the cost of
    installation and increasing site layout flexibility
  • Optional internal lining for DEF, water & JetA/AV Gas. 
  • Complete with STICO's 30-Year limited warranty
  • Features a durable non-slip grip application on top of tank to ensure OSHA safety compliance
  • Capacities range up to 40,000 gallons

Permatank® Benefits:

  • Double and triple-wall construction
  • Various backfill options allow for money-saving installation
  • Low-cost compartments and customization
  • Built to nationally-recognized STI Standards with
    strict third-party quality control inspection program
  • Braced Double Bulkheads
STI Permatank
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Protect The Environment - Buy Recyclable Steel Tanks
Compatible with a wide range of fuels and chemicals, including biodiesel and ethanol
Watco Tanks

Permatank® Double-Wall Jacketed Underground Steel Storage Tanks

  • Steel Tank Institute Permatank® and UL Labeled
  • Compatible with alternative fuels
  • Low-cost compartments and customization
  • Flat ends reduce installation costs
  • Provides safe and effective secondary containment
  • Capacities range up to 40,000 gallons
STI Permatank Underground Install

Permatank® Guideline Specification

 
General
  1. Provide Permatank® double‐wall jacketed steel‐fiberglass underground storage tanks.

Labeling
  1. Tanks shall bear the Steel Tank Institute Permatank® label.
  2. Underground tanks shall bear the appropriate Listing label.

Manufacturer
  1. Manufacturer shall be a licensed member company of the Steel Tank Institute and subject to Steel Tank Institute’s Quality Assurance program.
Product Description
  1. Tanks shall be manufactured per Steel Tank Institute Specification for Permatank®.
  2. Tanks shall be manufactured and listed following Underwriters Laboratories UL 58, Steel
    Underground Storage Tanks for Flammable and Combustible Liquids and UL 1746, External Corrosion
    Protection Systems for Steel Underground Storage Tanks or ULC‐S603.1, Standard for Corrosion Protection
    for Steel Underground Tanks for Flammable and Combustible Liquids.
  3. All tanks shall provide testable secondary containment and access for interstitial leak detection monitoring.

Trusted Watco Tanks Affiliates

Watco Tank Manufacturing Shot

U.S. Leader in UL & STI-Certified Solutions

Every Watco Tank undergoes independent inspections by UL and STI, with eight unannounced audits each year. Since the program's inception over 25 years ago, Watco has upheld a perfect inspection record, a standard achieved by only three STI-certified manufacturers nationwide.

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