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  • Writer's picturePlasTech Services Inc.

Fiberglass Tank Repair - How To Inspect A Fiberglass Tank

Updated: Jan 16, 2023

Fiberglass Tank Inspection: How to Inspect an FRP Tank

If you have a leaking fiberglass tank, you will need to take some time to diagnose the area of failure, gather materials and safety equipment, prepare the repair location, and apply the repair.

This is a difficult task, and it will take patience and expertise. If you need help inspecting or repairing your Fiberglass Tanks (i.e., FRP Tank), give us a call at 410-737-4700, send us an email at, or submit a request for a free quote at


Fiberglass tanks can leak for several reasons:

  1. Lining Failure from chemical attack (e.g., sodium hypochlorite, NzOCI or Sodium Hydroxide, NaOH).

  2. Nozzle Failure

  3. Penetration Failure from manufacturer's stock designs (pipes, valves, nozzles etc.)

  4. Impact damage from a forklift, motor malfunction, or falling equipment (e.g., mixing assemblies) or tools.

Areas to inspect: Tank Exterior, Tank Supports, Tank Identification, Tank Interior, Tank Testing, and Tank Manways.

Tank Exterior

The Contractor shall inspect the entire tank exterior, including ladders, handrails, mid rails, toe rails, flanges, nozzles, manway doors, pipes, pipe supports, and tank anchoring. Identify and document any:

  • Corrosion

  • Cracks

  • Crazing

  • Deformation

  • Insulation Failures

  • Paint Failures

  • Pitting

Tank Supports

Inspect the tank supports/feet and tank support pad/floor supporting the tank for signs of corrosion and/or deformation.

Tank Identification

Inspect the tank identification signs and the NFPA Hazard Identification Sign. Identify and document any damage or if a sign is no longer legible.

Tank Interior

  • Air Bubbles

  • Blisters

  • Burned Areas

  • Chips

  • Cracks

  • Crazing

  • Deformations

  • Delamination

  • Dry Spots

  • Edge Delamination

  • Foreign Inclusions

  • Pitting

  • Scratches

  • Surface Pinholes

  • Wrinkles

Tank Tests

FRP Tanks may need additional scanning and tests to determine Chemical Permeations, Degraded Areas, Thin Coverage Areas, Tank Thickness, or Overlapping of Corrosion barrier resin. Furthermore, a Barcol Hardness test should be performed at random areas of the tank interior. Barcol hardness readings shall be taken on both the bottom and sides of the tank in locations sufficient to evaluate the condition of the corrosion barrier.

Tank Manway Gaskets

As part of the inspection, it's essential to remove and replace the manway gasket after the Inspection or Repairs, and if Repairs are required, they should be authorized by the Owner.

New manway gaskets should be fabricated or repaired.

The FRP Tank Inspector should inspect, identify, and document any adverse changes to areas or items identified and/or repaired as part of a previous tank inspection or repair.


Tank entry BEWARE!

People involved with this job should be knowledgeable about reference materials published by API (American Petroleum Institute), NFPA (National Fire Protection Association), NIOSH (National Institute for Occupational Safety & Health), and OSHA (Occupational Safety & Health Administration).

Toxic fumes in fatal concentrations may result when working on a tank containing fuel oil, chemical liquids, or other flammable liquids. These vapors come from fuel sludge or scales in the tank or leaks from product lines not capped before entering the tank.

Applicable Material Safety Data Sheets (MSDS) for any material stored in the tank must be obtained from the tank operator and reviewed before entry into the tank. Lack of oxygen may occur if chemicals absorb or replace the oxygen in the tank or if the air becomes depleted due to improper or inadequate ventilation during tank entry—safe levels of oxygen range from 19.5% to 20.1%.

Fire and explosion may result from combustible liquid vapors inside the tank or other confined spaces. Fire and explosion may also be caused by sparks from tools, related electrical equipment, or static electricity. The three components of the fire triangle—fuel, oxygen, and ignition—are all required to sustain combustion. These three elements must be recognized, evaluated, controlled, and managed to create a safe work environment.

  • What kind of material does the tank hold?

  • Are there any special precautions for tank drainage or material relocation?

  • Is there a secondary containment failure?

  • Is this a confined space?

  • Do I need to supply fresh air to confined spaces?

  • What safety clothing and equipment are needed for the tank inspection and repairs?


Submit an inspection report to the owner to include all findings, recommendations, and pictures.

Make sure to abide by the currently adopted codes by the enforcing authorities (if applicable):

- American Water Works Association (AWWA) - National Fire Protection Association (NFPA) - Occupational Safety and Health Act (OSHA) - Society for Protective Coatings Standards (SSPC)

- Local Codes

- Plant-Specific Codes

The inspection report should be conducted according to client criteria and potentially according to the requirements of STI SP001 standards. It is also recommended to submit the information in print and digital format to the tank owner.

Tank Report

The inspection report should include Tank Descriptors, Tank Condition Assessments, Tank Measurements, Barcol Hardness Readings, and any associated pictures of the findings. Documenting inspection findings with photos is extremely important for future reference and confirmation of results.

Each Tank Inspection Report should include the following:

  1. Executive Summary

  2. Tank Name and/or Number

  3. Tank Data/Description (Material Type, Capacity, Dimensions – Height and Diameter, Manufacture Date, stored chemical, etc.)

  4. Location

  5. Foundation

  6. Shell

  7. Nozzles

  8. Floor

  9. Roof

  10. Ancillary Equipment

  11. Any other essential tank aspects

  12. Inspection Date

  13. Previous Inspection Date

  14. Inspection Findings

  15. UT Measurements

  16. Inspection Summary

  17. Recommendations

  18. Plans and or Diagrams

  19. Tank Repair Cost Estimate

  20. Photographs

  21. Tank Inspection Checklist

  22. Manufacturer data sheets

  23. NDE Records and certifications

When submitting the report, it will be helpful to submit the inspection drawings, checklist, photographs, manufacturers' data sheets, and NDE certifications as appendices.

The tank owner should be responsible for draining the tank to the lowest level possible using installed pumping equipment. The owner should also flush the tank of any remaining chemicals that may not have drained. After draining and flushing, the owner shall provide the inspector/contractor access to the tank and only re-fill the tank upon final written approval of the tank inspection and repair.


Drain or relocate and flush the tank of all liquid contents. The repair location will need to be completely dry and accessible for grinding, cutting, patchwork, and curing.

The tank may need to be repaired from the inside out. If this is the case, the tank must be flushed and cleaned out of all toxic chemicals. This will help you avoid further damage to the tank and make the repair process much more manageable. Furthermore, the owner will need to ensure that the tank is completely drained of any chemicals, flushed, removed any moisture or liquid, and relocated chemical contents to a storage container that has stored in-kind chemicals.


It's essential to submit a work schedule to the maintenance department to ensure scheduled activities don't adversely affect utility operations. It will be essential to communicate with the maintenance manager or tank owner to drain and flush the tank contents and allow time for drying and ventilation.

Be sure to submit all documentation on time, especially if the tank inspection is a public solicitation, procurement, or invitation for bid.

Need an FRP Tank Inspection?

If you need help inspecting or repairing your Fiberglass Tanks (i.e., FRP Tank), give us a call at 410-737-4700, send us an email at, or submit a request for a free quote at

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