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How to Fix a Crack in a Plastic Bathtub: In Easy Steps

Seal that crack in your plastic bathtub before the problem gets worse.

Plastic bathtubs are a great option when working on a tight budget, but they are not as robust as porcelain or ceramic versions. They can damage easily, especially with sharp or heavy objects.

Knowing how to fix a crack in a plastic bathtub is a vital skill, and it saves you dollars on buying a new tub.

Key Takeaways

  • Fix hairline cracks in acrylic tubs by cleaning, sanding, and using epoxy resin.
  • Repair cracked plastic bathtubs with fiberglass mesh, sandpaper, and patch filler.
  • Flex Seal can provide a temporary fix for cracked bathtubs but is not a permanent solution.
  • Maintain plastic tubs by avoiding abrasive cleaners, heavy objects, excess weight, and scourers.

How to Fix a Hairline Crack in an Acrylic Tub

Acrylic tubs are made from polymethyl methacrylate, which is a softer plastic than resin plastic tubs. You are more likely to get hairline cracks in this type of bathtub.

Hairline cracks are the easiest to fix, provided you deal with the issue immediately. If you leave it, the gap expands, and then you have a more complex task to repair.

What You’ll Need

  • Putty knife.
  • Power drill.
  • 1/4-inch drill bit.
  • Clean rag.
  • Nylon paintbrush.
  • 120-grit sandpaper.
  • 240-grit wet and dry sandpaper.
  • Epoxy resin.
  • Nail polish gel coat.
  • Hairdryer (optional).
  1. Clean the bath just as you would during your usual cleaning regime. Allow the tub to dry for 24 hours before attempting a repair. You could use the hairdryer to speed up this process.
  2. Locate the crack and drill a 1/4-inch hole on either side of the split. This helps the sealant grip the bathtub and close the gap.
  3. Grab the 120-grit sandpaper and gently sand around the hairline split. Using too much force will damage the plastic surface and create a more significant problem.
  4. Wipe the area clean with a damp rag. Don’t leave any plastic dust particles because it will affect how the epoxy resin bonds to the surface.
  5. Leave the tub to dry for 12 hours, or speed up the process with a hairdryer.
  6. Follow the instructions on the epoxy packaging to get the correct mix between epoxy and hardener. This Epoxy resin kit comes with all the gear needed, including gloves.
  7. Spread the epoxy mix onto the bathtub crack using the putty knife and leave to dry for 10 to 12 hours.
  8. Wet the 240-grit sandpaper and gently rub it over the surface until the epoxy is smooth.
  9. Wipe the area clean with a damp rag and leave to dry for another 12 hours.
  10. To finish the repair, lay down a layer of gel coat enamel, like this nail polish kit.

How to Fix a Cracked Plastic Bathtub

Plastic tubs differ from acrylic tubs because they are constructed from a resin-based plastic, which is more brittle and prone to larger cracks.

Plastic bathtub crack repair is crucial if you want to save your tub and save money. Before you start, you’ll need the right tools.

What You’ll Need

  • Putty knife.
  • Fiberglass mesh.
  • 120-grit sandpaper.
  • 240-grit wet and dry sandpaper.
  • Utility knife.
  • Paintbrush.
  • Patch filler (caulk, repair kit, or model glue).
  • Damp rag.
  • Caulk gun.

With a Plastic Bathtub Repair Kit

Bathtub repair kits have all the gear you need to fix that cracked vinyl bathtub. This Tub and Tile kit is ideal because you can also repair tiles on the wall or floor.

  1. Clean the bathtub like you would during a regular cleaning regime. If the surface is wet, it will hamper the adhesion of the repair tape and epoxy resin. Let the surface dry for 24 hours before moving to the next steps.
  2. Fiberglass mesh works on cracks with a maximum span of 1/4 inches. Ensure that it overlaps each side of the gap by half an inch.
  3. Sand the bathtub around the crack to create a better bonding surface. Use the 120-grit sandpaper and rub gently.
  4. Mix your epoxy using the tools provided.
  5. Apply the filler to the gap with the plastic putty knife and press the mesh so that it bonds with the filler material. Apply a second filler coat to cover the mesh and seal the gap.
  6. Scrape away the excess filler with the putty knife and leave it to dry following the manufacturer’s recommended curing time.
  7. Use wet and dry 240-grit sandpaper with a small amount of water to rub the filler smooth. When you are happy with the results, clean the area using a damp rag.
  8. Leave the tub to dry for 12 hours before applying a gel coat to seal the repair. Leave it to dry for another four hours.

With Waterproof Caulk

Waterproof caulk is the most convenient way to fix a broken bathtub. It comes in handy tubes and is easy to dispense.

Top Tip

Cut the caulk nozzle at the correct size for the crack so you can lay the caulk in one smooth strip. If the nozzle is too thin, you will need a couple of messy caulk lines.

  1. Clean the bathtub to remove any grime or soap scum lingering on the surface. Use a detergent like this Better Life cleaning agent to cut through grease and mold. It’s a plant-based product that’s kind to the planet.
  2. Leave the tub to dry for 24 hours.
  3. Use the 120-grit sandpaper to sand around the crack to give the caulk better adhesion.
  4. Wipe the area with a damp rag and wait while the tub dries.
  5. Cut the caulk nozzle to the correct size to match the gap’s width.
  6. Load the caulk tube into the caulk gun.
  7. Hold the caulk at 90 degrees and gently squeeze the trigger. Work from the furthest end of the crack, pulling the caulk towards you.
  8. When you reach the nearest end of the gap, lift the caulk and press the release lever to remove the spring to stop the caulk from flowing.
  9. Wet your finger, run it along the caulk line to smooth it into the crack, and wipe the excess on the damp rag.
  10. Wait for the recommended drying time for the caulk to set.
  11. Sand the caulk with wet and dry sandpaper until the surface is smooth. Wipe the area clean with a damp rag.
  12. Wait a couple of hours while the caulk sets before using the tub.

With Model Glue

Model glue sticks to plastic, so it stands to reason that it will fix that crack in your acrylic bathtub.

  1. Clean the bathtub to remove traces of grease, grime, and soap.
  2. Sand the area immediately around the crack with 120-grit sandpaper.
  3. Wipe the surface clean with a damp rag to remove all traces of the plastic dust.
  4. Wait while the bathtub dries.
  5. Remove the lid from the model glue and run a line along the crack.
  6. Leave it to set for the specified time according to the instructions.
  7. Sand the glue smooth using the 240-grit wet and dry sandpaper.
  8. Wipe the surface clean with a damp rag

Take Note

Model glue is only suitable for narrow cracks. For more substantial gaps, try using repair tape or fiberglass mesh.

Will Flex Seal Fix a Cracked Bathtub?

Flex seal will provide a temporary fix but don’t rely on it as a permanent repair. It will make your gap watertight, but it will eventually give under the weight of the water. You can’t sand or polish flex seals either, which isn’t ideal for concealing patch repairs.

Tips for Fixing Cracks in a Plastic Tub

We all want an easy life, and when it comes to repairing cracks in a plastic tub, we’ll take whatever cheat or hack we can.

Always Do the Prep Work

The prep work may be dull or tedious, but the more effort you make at this stage, the better the results will look. Cleaning and sanding are the best ways to get your bathtub filler to adhere, and the better it sticks, the longer the repair lasts.

Spot Test the Glue

Not all glues are compatible with plastic, so you should perform a spot test on your bathtub. The best adhesive is plastic glue because it is formulated to work with acrylic bathtubs; however, it may not offer the strongest repair.

Wear Gloves and a Face Mask

When you work with epoxy resin, always wear gloves and a face mask. Resin is toxic and can burn skin and lungs if it makes contact. It also releases strong odors, so work in well-ventilated areas with open windows.

Use Fiberglass Mesh

Fiberglass repair mesh, like this Red Devil Patch Repair, is ideal for fixing cracks that span up to 1/4-inch. Make sure that you have enough to cover half an inch on either side of the gap.

When to Replace a Bathtub

If you’ve repaired the crack and it keeps coming back, it’s time to throw out the old tub and get a new one. Fixing a split is sometimes a temporary repair, so you are possibly fighting a losing battle.

Some patch repairs may look okay, but all you are doing is covering up a weak spot in the bathtub, and that’s where it can come back to haunt you.

How to Care for a Plastic Tub

Female hand in blue gloves cleaning dirty bathtub with spray

The best way to avoid replacing your bathtub is to look after it. What are the best tips for maintaining a plastic tub? Let’s take a look.

Avoid Abrasive Cleaners

Abrasive tub cleaners will scratch and damage the tub’s surface, making it look unsightly. Dirt will cling to the surface and stain the sides of the tub. Once you scuff your plastic tub, it will never look as good again.

Mold may also take hold, which makes your bath look dirty.

Avoid Dropping Heavy Objects

Nothing kills your plastic bathtub like a dropped heavy item. Avoid spanners, wrenches, and other tools because they split and crack the plastic on impact. Keep your kids away from the bathroom with heavy objects or risk significant damage.

Avoid Excess Weight

Bathtubs have a maximum weight limit, so avoid overloading the bathtub. The more strain you put on the frame and supports, the more likely the tub will crack.

Avoid Scourers

Try using soft cloths or sponges without a scrubbing pad. Scourers are bad for plastic bathtubs. While they may state they are no-scratch, repeated use scuffs the surface and dulls the tub’s finish.

Plastic Fantastic

Plastic bathtubs can last years with the proper cleaning regime. They need care and attention to keep them looking good, which means making repairs when necessary. Knowing how to fix a crack in a plastic bathtub could save you big bucks and a world of inconvenience.

So, the next time you spot a small crack, don’t ignore it; fix it before it gets worse.

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About the Author

Mark Weir

Mark spent 24 years working in real estate, so he knows his way around a home. He also worked with contractors and experts, advising them on issues of planning, investments, and renovations. Mark is no stranger to hands-on experience, having renovated his own home and many properties for resale. He likes nothing better than seeing a project through to completion.