What is the KBS Plastic Tank Sealer System?
The KBS Plastic Tank Sealer System is a three-step fuel tank sealing kit that cleans, primer etches, and permanently seals the inside of hard plastic fuel tanks so fuel stops weeping through the tank walls. The kit pairs KBS Klean, Fusion SEP plastic primer etch, and Gold Standard Tank Sealer, a single-component moisture-curing sealer that reaches full cure in 96 hours and resists gasoline, diesel, E10, E15, and E85.
55°–82°F
Ideal Temp Range
Single Coat
Pour, Coat & Drain
E10 / E15 / E85
Fuel Compatible
Plastic fuel tanks on lawn tractors, ATVs, generators, and outdoor power equipment turn porous with age, and ethanol-blended fuel accelerates the process. The result is a tank that is not visibly cracked but still smells of gas, leaves a damp film on the outside, or slowly loses fuel. That is fuel vapor weeping straight through the plastic wall.
Metal tank kits solve a rust problem, so they lead with an acid etch. Plastic has no rust to remove and almost nothing sticks to it, so this system substitutes Fusion SEP, a primer etch that gives Gold Standard Tank Sealer a surface it can bond to. Once cured, the silver coating flexes with the tank instead of cracking off it, and stays impervious to gasoline, diesel, and alcohol-blended fuels.
Safety first: always wear protective gloves and safety glasses, and always work in a well-ventilated area. Gold Standard Tank Sealer is a moisture-curing isocyanate coating with a 103°F flash point. Heed all warnings and caution notices on the product labels.
Seal the tank once and stop replacing it. Satisfaction guaranteed!
Every kit ships with all three steps plus gloves, a stir stick, and printed directions. Container sizes vary by kit.
Before You Begin: Check Your Tank for Holes and Cracks
It is important to verify the condition of your plastic tank before you start. Make sure the tank does not have any holes or cracks in it. If your tank does have holes or cracks, patch those FIRST before you start the process.
Tank Sealer is a coating, not a filler. Gold Standard Tank Sealer stops fuel from weeping and seeping through porous plastic walls, but it will not bridge an open hole or a split seam. Sealing over unrepaired damage wastes the kit and leaves the tank leaking.
Patch the outside of the tank first with KBS NuMetal Epoxy Putty or KBS Patch: clean the area with KBS Klean, let it dry, scuff with 320 grit sandpaper, then follow the NuMetal or KBS Patch instructions and allow 12 hours of cure time before sealing the inside of the tank.
Yes, if the tank has any hole or crack. The KBS Plastic Tank Sealer System coats a porous tank wall to stop weeping, but Gold Standard Tank Sealer will not bridge an open hole or a split seam. Inspect the tank before you buy or begin, and patch every hole and crack from the outside first, then seal the inside.
How Do I Tell the Difference Between a Weeping Tank and a Cracked Tank?
A weeping plastic tank has no visible opening. The outside feels tacky or damp, the tank smells strongly of fuel, and the level drops slowly with no puddle underneath. A cracked or holed tank drips or streams from one identifiable spot, usually along a mold seam, at a mounting boss, or where the tank has been struck or rubbed through.
If you are unsure, drain the tank, wipe it completely dry, and fill it with water. Water will find a hole that fuel vapor was only weeping through, and it costs nothing to check.
How Do I Patch a Hole or Crack in a Plastic Fuel Tank?
Patch plastic tanks from the outside using KBS NuMetal Epoxy Putty or KBS Patch. Clean the outside of the tank with KBS Klean and let it dry. Scuff the area to be patched with 320 grit sandpaper, then apply the patch material per its own instructions. Allow NuMetal or KBS Patch to cure for a full 12 hours before you move on to sealing the inside of the tank.
Once the patch has cured, the tank is ready for Step 1 of the sealing process. Any leftover Gold Standard Tank Sealer can be brushed over the outside of the repair to reinforce it.
Patch First. Then Seal.
Sealing over an unrepaired hole or crack will not stop the leak, and cured Tank Sealer cannot be removed by any solvent. Get the repair right before the sealer goes in.
Shop NuMetal Epoxy Putty
Shop KBS Patch
Every KBS Plastic Tank Sealer System kit contains three products applied in order: KBS Klean to degrease the tank interior, Fusion SEP to primer etch the plastic so the coating can bond, and Gold Standard Tank Sealer to permanently seal the tank. Nitrile gloves, a stir stick, and printed step-by-step directions are included in all three kit sizes.
Step 0
Inspect & Patch
Check the tank for holes and cracks before anything else. Patch them from the outside with NuMetal Epoxy Putty or KBS Patch and allow 12 hours to cure. Tank Sealer coats a porous tank; it does not fill an open hole.
Step 1
KBS Klean
Water-based heavy-duty cleaner and degreaser. Mix 1:1 with hot water, pour it into the tank, and rotate at intervals so it reaches every surface. Rinse until the water runs clear, then let the tank dry bone dry. The cleaner the tank, the stronger the bond.
Step 2
Fusion SEP
Plastic primer etch and adhesion promoter. Stir, do not shake. Pour the full can in, roll the tank for up to 15 minutes until every surface is coated, then drain the excess immediately. Fusion SEP is designed to work as a thin film and must never be left to puddle.
Step 3
Gold Standard Tank Sealer
Single-component, ready-to-use silver sealer. Stir thoroughly without whipping, pour it in, and roll the tank for up to 30 minutes. Drain all excess until it stops dripping, rotating side to side every 5 minutes. Allow 96 hours for full cure.
Timing note: seal the tank within 10 days of cleaning and prepping it. A prepped tank left sitting picks up moisture and contamination, and the adhesion Fusion SEP created starts working against you rather than for you.
The KBS Plastic Tank Sealer System is built for hard plastic fuel tanks, including HDPE and other rigid molded plastics, the kind permanently mounted in lawn tractors, riding mowers, ATVs, generators, and small engine equipment. The system is not suitable for flexible plastic containers, and it is not the right product for metal tanks.
- Hard plastic and HDPE fuel tanks
- Rigid, molded tanks that hold their shape when squeezed. These are the tanks this system was formulated for.
- Tanks that weep or seep rather than drip
- Porous tank walls that let fuel vapor pass through, often after years of ethanol-blended fuel. This is the exact failure the sealer stops.
- Repairable tanks with patched damage
- Tanks with holes or cracks already patched with NuMetal Epoxy Putty or KBS Patch and cured for 12 hours.
- Not for flexible plastic containers
- Portable gas cans, jerry cans, and any container that bends or compresses when squeezed. Flexing breaks the bond of the cured coating.
- Not for metal tanks
- Steel, aluminum, and fiberglass tanks need rust removal and metal etching instead of a plastic primer. Use the KBS Tank Sealer Kits for metal tanks.
- Not for unrepaired holes or cracks
- Patch first, cure 12 hours, then seal. Sealer coats a tank; it does not fill an opening.
The KBS Plastic Tank Sealer System is one of the few tank sealing kits engineered for plastic rather than adapted from a metal kit. Fusion SEP primer etch replaces the rust treatment step, so Gold Standard Tank Sealer bonds to a substrate that normally rejects coatings, then cures into a flexible 76 percent solids film that moves with the tank.
- Built for plastic, not adapted to it: Fusion SEP primer etch is the step that makes a permanent bond on HDPE and rigid plastic possible. Metal kits have no equivalent.
- Stops weeping permanently: the cured film closes off the porous tank wall so fuel and fuel vapor no longer pass through it.
- Flexes with the tank: a smooth, ceramic-like finish with high flexibility and toughness that expands and contracts with the plastic instead of cracking or peeling.
- Handles modern fuel: impervious to gasoline, diesel, and alcohol-blended fuels including E10, E15, and E85, plus strong resistance to acids, alkalis, salts, solvents, and hydraulic fluids.
- Single component, no mixing: Gold Standard Tank Sealer is ready to use straight from the can. Stir it, pour it, roll it, drain it. No hardener, no ratios, no pot life clock the moment you open it.
- Single thin coat: one properly drained coat does the job at a minimum 3 mil dry film thickness.
- Proven durability: 2000 hours of ASTM B-117 salt spray at 95°F with no noticeable change, and no noticeable change after 168 hours of continuous contact with 93 octane fuel, diesel, MEK, xylene, brake fluid, or hydraulic fluid.
- Complete kit: all three steps plus nitrile gloves, a stir stick, and detailed printed instructions in every size.
- Made in the USA: manufactured in Valparaiso, Indiana and shipped factory direct, same day.
Use the KBS Plastic Tank Sealer System on any hard plastic fuel tank in outdoor power equipment, powersports, and small engine machinery, from riding mowers and generators to ATVs, snow blowers, and personal watercraft. Kit sizes cover tanks from under 5 gallons up to 25 gallons.
- ✓ Lawn Mowers & Garden Tractors
- ✓ Riding Mowers & Zero-Turn Mowers
- ✓ String Trimmers & Weed Eaters
- ✓ Leaf Blowers & Hedge Trimmers
- ✓ Garden Tillers
- ✓ Log Splitters
- ✓ Portable Generators
- ✓ Pressure Washers
- ✓ Portable Water Pumps
- ✓ Chipper/Shredders
- ✓ Snow Blowers & Snow Throwers
- ✓ ATVs & UTVs
- ✓ Go-Karts & Mini Bikes
- ✓ Dirt Bikes
- ✓ Small Boats & Outboard Motor Tanks
- ✓ Personal Watercraft (PWC)
- ✓ Walk-Behind Cultivators
- ✓ Irrigation & Sprayer Pumps
- ✓ Plate Compactors
- ✓ Standby & Portable Generator Sets
Choose the KBS Plastic Tank Sealer System kit by tank capacity, not by how much surface looks porous. The 0 to 5 gallon kit carries 8 oz of each product, the 5 to 12 gallon kit carries a quart of KBS Klean plus a pint each of Fusion SEP and Gold Standard Tank Sealer, and the 12 to 25 gallon kit carries a full quart of all three.
| Kit Size | KBS Klean | Fusion SEP | Gold Standard Tank Sealer |
|---|
| 0–5 Gallon Tank | 8 oz | 8 oz | 8 oz |
| 5–12 Gallon Tank | Quart | Pint | Pint |
| 12–25 Gallon Tank | Quart | Quart | Quart |
All three kit sizes also include nitrile gloves, a stir stick, and detailed application instructions. For reference, a quart of Gold Standard Tank Sealer covers roughly 100 square feet of porous surface at 2 mils, and a gallon covers roughly 400 square feet, though coverage inside a tank varies with baffles, surface profile, and how thoroughly the excess is drained.
Working windows: roll Fusion SEP for up to 15 minutes, then drain. Roll Gold Standard Tank Sealer for up to 30 minutes, then drain until it stops dripping, rotating the tank side to side every 5 minutes.
Pro Tip: if your tank capacity falls right on a boundary, size up. Running short of sealer partway through a tank is not recoverable. Drained sealer has been exposed to atmospheric moisture and cannot be saved or reused, so a partial second attempt from an opened can is not an option.
Not sure of your tank's capacity? Check the equipment owner's manual, or use our tank sealer sizing guide.
Sealing differs from replacing in that the KBS Plastic Tank Sealer System restores the tank you already have for a fraction of a replacement tank's cost, and the cured coating is more fuel resistant than the bare plastic underneath it. Replacement gives you a new tank but does nothing to prevent the same ethanol-driven porosity from returning.
| | KBS Plastic Tank Sealer System | Replacing the Tank |
|---|
| Works on discontinued or obsolete tanks | Yes, the original tank is retained | No, depends on a part still being made |
| Ethanol resistance after the job | Coated interior rated for E10, E15, and E85 | Same bare plastic that became porous the first time |
| Repairs holes and cracks | No, patch with NuMetal or KBS Patch first | Yes, damage is replaced outright |
| Time to back in service | 96 hours full cure before adding fuel | As soon as the new tank is fitted |
| Fit and mounting | Original tank, original fit | Aftermarket fit varies by supplier |
Replacement is the better call when the tank is warped, structurally split beyond a patch, or when an inexpensive OEM tank is still available off the shelf and downtime matters more than cost. Sealing wins when the tank is sound but porous, or when the part is discontinued and a replacement is expensive or simply gone.
Allow the sealed tank to air dry naturally in a well-ventilated area for a full 96 hours before adding fuel. Gold Standard Tank Sealer is touch dry in 4 to 6 hours at 77°F and 50 percent humidity, but touch dry is not cured. Test the tank for leaks by filling it with water before you refill it with fuel.
- Do not force the cure
- Keep the tank out of direct sun and away from direct heat. Heating will not cure the sealer faster and may hinder adhesion.
- Coat every surface
- Any spot left uncoated stays vulnerable to alcohol-blended fuel. Foaming or bubbling means sealer pooled and did not drain, and the only fix at that point is to strip the tank and start over.
- Use the leftovers immediately
- Brush any remaining sealer onto the outside of the tank to reinforce patched holes and seams. Drained sealer cannot be saved or reused.
- Dispose of it safely
- Let leftover sealer harden in the can with the lid OFF. Sealing the lid before curing finishes can build pressure and pop it. Dispose of hardened sealer per federal, state, and local regulations.
- Clean up right away
- Use KBS #1 Thinner or lacquer thinner immediately. Cured sealer cannot be removed by any solvent.
Read the Full Application Directions
How To Seal a Plastic or Polyethylene Gas Tank
The full walkthrough for plastic and poly tanks, including why plastic needs a primer etch instead of a rust treatment.
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Plastic Tank Sealer Application Directions
Step-by-step directions with temperatures, working windows, cure times, and the tank inspection you do before Step 1.
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Gold Standard Tank Sealer Technical Data Sheet
Solids, VOC, viscosity, film thickness, dry times, salt spray results, and the full chemical contact test table.
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The KBS 3-Step Tank Sealing System Explained
Why clean, prep, and seal has to happen in that order, and what goes wrong when a step gets rushed or skipped.
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Tip of the Month: Patience When Using Tank Sealer
The single most common cause of a failed tank seal is rushing the drain and the cure. Here is what patience looks like.
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Before and After Project Photos
Real customer tank sealing and rust prevention projects, before and after, sent in from the shop and the driveway.
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Have questions before you buy? Find answers to the most common plastic tank sealing questions below, or
select your kit size and get it shipped same day.
The KBS Plastic Tank Sealer System is a three-step kit that permanently seals hard plastic fuel tanks that are weeping or seeping fuel. It contains KBS Klean to degrease the tank interior, Fusion SEP to primer etch the plastic so a coating can bond to it, and Gold Standard Tank Sealer, a single-component moisture-curing sealer that forms a fuel-impervious film. Nitrile gloves, a stir stick, and printed instructions are included in every kit size.
Yes, if the tank has any hole or crack, patch it first. It is important to verify the condition of your plastic tank before you start. Make sure the tank does not have any holes or cracks in it. If your tank does have holes or cracks, patch those FIRST before you start the process. Gold Standard Tank Sealer coats a porous tank wall to stop weeping, but it will not bridge an open hole or a split seam.
Patch from the outside with KBS NuMetal Epoxy Putty or KBS Patch. Clean the area with KBS Klean, let it dry, scuff with 320 grit sandpaper, apply the patch material per its instructions, and allow 12 hours of cure time before sealing the inside of the tank.
This kit is designed for hard plastic fuel tanks, including HDPE (high-density polyethylene) and other rigid molded plastics. Those are the tanks found in lawn tractors, riding mowers, ATVs and UTVs, portable generators, snow blowers, pressure washers, and similar small engine equipment. A qualifying tank is rigid, holds its shape when squeezed, and is permanently mounted in the machine.
No. This kit is not suitable for flexible plastic containers such as portable 5-gallon gas cans and jerry cans. Flexible containers bend and compress in normal use, which breaks the bond of the cured sealer film. If the container flexes when you squeeze it, it is not compatible with this kit.
Not sure if your tank qualifies? Hard plastic tanks are rigid and permanently mounted in the equipment.
Contact our technical team if you need help identifying your tank type.
Fusion SEP is a primer etch formulated for plastic tank interiors. Plastic cannot be treated with the rust removers and acid etches used on metal tanks, so Fusion SEP creates the adhesion bond between the plastic and the sealer instead. Stir the can thoroughly without shaking it, pour the entire contents in, roll the tank for up to 15 minutes until all surfaces are coated, then drain the excess immediately. Fusion SEP works as a thin film only and must never be allowed to puddle.
Once cured, Gold Standard Tank Sealer is impervious to gasoline, diesel, and ethanol-blended fuels including E10, E15, and E85. In 168-hour continuous contact testing it showed no noticeable change against 93 octane fuel, diesel fuel, MEK, xylene, brake fluid, hydraulic fluid, hydrochloric acid, and phosphoric acid, and it survived 2000 hours of ASTM B-117 salt spray at 95°F with no noticeable change.
Allow at least 96 hours, or 4 days, before adding fuel to a newly sealed tank. Gold Standard Tank Sealer is touch dry in 4 to 6 hours at 77°F and 50 percent humidity inside an enclosed tank, but touch dry is not cured. Let the tank air dry naturally in a well-ventilated area and keep it out of direct sun and away from direct heat, since heating will not speed the cure and may hinder adhesion. Always test for leaks by filling the tank with water before refilling it with fuel.
The ideal working temperature range for the KBS Plastic Tank Sealer System is 55°F to 82°F in a well-ventilated area. Gold Standard Tank Sealer is moisture curing, so both temperature and humidity affect how fast it sets. Store the unopened product in cool, dry conditions between 41°F and 95°F and out of direct sunlight.
Choose the kit by your tank's fuel capacity. The 0 to 5 gallon kit includes 8 oz each of KBS Klean, Fusion SEP, and Gold Standard Tank Sealer. The 5 to 12 gallon kit includes a quart of KBS Klean plus a pint each of Fusion SEP and Gold Standard Tank Sealer. The 12 to 25 gallon kit includes a quart of all three. If your capacity falls on a boundary, size up, because drained sealer cannot be saved or reused and running short partway through a tank is not recoverable.
No. This kit is built specifically for plastic. Metal tanks need a different prep process, including rust removal and metal etching with RustBlast rather than a plastic primer etch. For steel, aluminum, and fiberglass fuel tanks, use the KBS Tank Sealer Kits for metal tanks, available for tanks from 1 to 50 gallons.
