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  • Writer's picturePlasTech Services Inc.

Interstitial Leak In A Fiberglass Tank

Updated: Feb 20, 2023

Interstitial Leak Repair in Fiberglass Tanks

PlasTech Services Inc. provides professional industrial maintenance services that specialize in interstitial leak repair of fiberglass tanks. Modern fiberglass double-walled storage tanks feature an inner fiberglass wall tank surrounded by a protective outer fiberglass containment vessel. These tanks are designed to contain any spilled liquid, but if the space between the two vessels becomes compromised and begins to leak, it can create a dangerous or expensive situation.

Understanding Interstitial Space

The area between the two walls of chemical storage tanks is known as the interstitial space or annular space. Even when a tank is empty, the interstitial space can still become filled with liquid and cause leaks that can be costly and hazardous to your operation. If you suspect a leak in your fiberglass tank, it’s important to contact a professional service technician right away for an inspection and prompt repair solutions.

Assessing Your Tank for Leaks

If you notice signs of leakage from your fiberglass tank, you should first check for visible signs of damage on the exterior such as cracks, holes, bulges or other deformations. However, some leaks may not be visible from outside so you should also look for damp spots around the seals or joints connecting one section with another in order to identify any potential sources of fluid intrusion. Since most modern tanks are equipped with sensors that detect changes in pressure levels or temperature variations due to leaks, inspecting these data logs may provide valuable information as well. Lastly, be sure to assess whether there is adequate containment capacity should any liquids spill onto surrounding properties during repairs.

We provide several articles on Fiberglass Tank Inspections here:

Steps to Repairing Interstitial Leaks

1) Drain your tank

Once you have identified and isolated the source of leakage in your fiberglass tank, start by draining out all liquids inside it so that repairs can begin safely and without interruption. If necessary utilize pumps or vacuum trucks for faster dewatering processes.

2) Remove damaged sections

Inspect all accessible areas around the affected area(s) of your tank in order to remove damages sections/pieces before attempting repairs on them. In cases where more extensive damage appears present further steps may need to be taken such as relining or replacing parts depending on budget constraints and site requirements.

3) Make temporary patches

After cleaning up all areas around damage sections apply temporary patches with epoxy, resin, and fiberglass mat before replacing them completely with new pieces or conducting any additional relines needed on them (this way they will remain protected from further corroding). A full tank reline may be necessary if the source of the leak cannot be detected.

4) Replace damaged components

Replace any permanently damaged components either through relining existing materials using seamless thin layers (ideal for minor surface damages) or installing brand new pieces (such as panels/sections).

5) Conduct testing

After all repairs have been completed conduct thorough testing procedures such as hydrostatic tests in order ascertain whether they were successful at fixing all potential sources of leaking and preventing future reoccurrences when filled back up with liquids again later on down line operations wise speaking

6) Consider Installing Sensors

Various sensor manufacturers produce interstitial leak detectors that you may find helpful. These sensors, placed in the bottom of the interstitial space of the tank, will sound alarms if a leak it detected.

If you have an interstitial leak, it's important to contact us at 1-410--737-4700 or request a free quote at

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