How to Seal a Plastic Gas Tank

Co-authored by Ed Beery and Eric McClure

Last Updated: October 24, 2024 Approved

Plastic gas tanks are in high demand in the world of motorcycle racing and ATV enthusiasts. A plastic gas tank can weigh less than half of a comparable metal gas tank and it is easy to mold into shapes to fit odd configurations. Seamless gas tanks seldom leak and are impervious to the rust and corrosion that affect metal tanks. If a plastic fuel tank does sustain small holes or tears, there are several fairly easy ways to make the repair.

Method 1

Method 1 of 3:

Seal Plastic Gas Tank with Epoxy Glue

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Sand the area around the hole or crack, and clean the area with a shop cloth saturated with rubbing alcohol.^{[1]
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^{[2]
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Research source} Cut a fiberglass patch large enough to cover the opening and overlap it.

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Apply more epoxy to the patch and surrounding area, pressing firmly to saturate the patch.

Method 2

Method 2 of 3:

Seal Plastic Gas Tank with a Plastic Welder

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Tell the salesperson what you are doing with it to ensure that you get the correct rods.
Drain the gasoline from the tank, and allow it to dry both inside and outside. Don protective eye gear, a welding helmet and welding gloves.
Start at an edge and run the bead completely around the opening. Then begin crossing over the hole, allowing the rod to fill in the hole completely.^{[3]
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Method 3

Method 3 of 3:

Seal Plastic Gas Tank with a Soldering Gun

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^{[4]
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Research source} Lightly sand the perimeter of the area to be repaired.
Move the gun from side to side to push the plastic back into the trench. While the plastic is still soft from the soldering, lay the plastic patch over the area. Continue moving the soldering gun over the area to smooth the plastic, and fuse them together.^{[5]
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Mix a 2 part epoxy glue, and cover the entire area of the patch.^{[6]
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Research source} Allow to set up, sand and spray on a coat of plastic paint if desired.

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Question

Is Flex Seal gasoline resistant?

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This answer was written by one of our trained team of researchers who validated it for accuracy and comprehensiveness.

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According to the manufacturer’s website, Flex Seal is not a good choice for sealing gasoline tanks. It’s not made to withstand a lot of heat or pressure, and it’s not recommended for use with flammable liquids, such as gasoline.

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How do you fix a plastic gas tank on a lawnmower?

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A fiberglass repair patch will work well for this job. Drain the tank and let it dry completely first, and don’t forget to sand the area around the leak or hole so that the adhesive compound can adhere properly.

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Will Teflon tape seal in gasoline?

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No, the gasoline will eventually break down the tape. If you want a quick and easy fix, a fiberglass patch is a better option.

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Tips

Using epoxy glue is the easiest way to seal a plastic fuel tank, but it sometimes fails after a short time.

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If using a plastic welder for the first time, practice before attempting to seal the plastic gas tank. The rental store should be able to work with you to ensure that you have no problems.

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Warnings

A plastic welder is safe around gasoline and gasoline fumes, as it has a very high flash point. However, use common sense and do not use near open flames.

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