A small crack in your tub might not seem like a big deal, but it can turn into a bigger problem fast. Water can get in, cause leaks, or damage the floor under your tub. The good news? You can fix most cracks yourself. You just need the right tools and a little patience.
This guide will walk you through how to fix cracks in a bathtub, step by step. You’ll also learn what kind of tub you have, what repair kits work best, and when it’s better to call a pro.
What Kind of Crack Are You Dealing With?
Before you start, take a close look at the crack.
- Hairline cracks: These are small surface cracks. They’re the easiest to fix.
- Stress cracks: These happen when something hits the tub or if the tub flexes too much.
- Deep cracks or holes: If the crack goes all the way through, water might be leaking under the tub.
If the crack is longer than 6 inches or near a drain or faucet, fixing it might be more work than it’s worth. But most small and medium cracks are fixable with a repair kit.
Step 1: Figure Out What Your Tub Is Made Of
You can’t fix a crack without knowing your tub material. The repair process depends on this.
Most common tub materials:
- Acrylic: Feels smooth and slightly warm. Light and flexible.
- Fiberglass: Lighter than acrylic. Often sounds hollow when you tap it. You might see small glass fibers underneath.
- Porcelain or cast iron: Heavier and colder. These usually chip rather than crack.
If you’re not sure, look under the tub or around the edge. Acrylic is glossy and flexible. Fiberglass looks a bit dull and may have strands underneath.
Step 2: Get the Right Tools
Here’s what you’ll need:
- A tub repair kit (make sure it’s made for your tub type)
- Sandpaper (medium and fine)
- Rubbing alcohol or acetone
- A plastic putty knife or spreader
- Clean cloths or paper towels
- Gloves
- A face mask (for fumes)
- A fan or open window
Some fiberglass repairs may also need a small drill and a bit to make stop holes. More on that below.
Step 3: Clean the Area
Start by cleaning the cracked area with soap and water. Then wipe it down with rubbing alcohol or acetone. You need to get rid of all soap, oil, and dirt. If the area isn’t clean, the repair won’t stick.
Let the area dry fully before moving on.
Step 4: Sand the Area Lightly
Use medium-grit sandpaper to rough up the surface around the crack. This helps the filler stick better. Be gentle and sand about an inch or two around the crack. Wipe away any dust with a clean cloth.
If you’re fixing a fiberglass tub, drill a small hole at each end of the crack. These stop the crack from spreading. Only do this if the crack is more than two inches long.
Step 5: Mix and Apply the Repair Filler
Most kits come with a filler and a hardener. You need to mix together these parts together. Follow the instructions closely. Mix just enough for one use. It can dry fast.
Use the putty knife to press the mixture into the crack. Smooth it out as best as you can. For deep cracks, you may need to apply a second layer after the first one dries.
Let it sit for as long as the instructions say. Most fillers take at least 6 hours. Some take up to 24.
Step 6: Sand Again and Apply Finish (If Needed)
Once it’s fully dry, use fine-grit sandpaper to smooth the area. Wipe off any dust.
Some kits include a top coat or finish. This helps seal the patch and makes the fix blend in better. Apply it if your kit includes it and let it dry fully.
If you followed all the steps and used the right materials, the crack should now be sealed. Your tub is safe to use again once everything is dry.
A Few Extra Tips for Acrylic Tubs
Acrylic tubs are soft and scratch more easily than fiberglass. When sanding, use lighter pressure and be extra gentle. Also, avoid strong cleaners going forward. They can wear down the surface.
If your tub flexes under your feet, that means it doesn’t have enough support under it. You might want to add foam or support underneath to stop more cracks in the future.
Common Mistakes to Avoid
- Skipping the cleaning: Dirt and oils can keep the repair from sticking.
- Using the wrong repair kit: Make sure your kit matches your tub type.
- Not letting it dry fully: If you use the tub too soon, you’ll ruin the repair.
- Not sanding enough: Sanding before and after is key to a smooth, lasting fix.
When Should You Call a Pro?
Not every crack can be fixed with a kit. Call a bathtub repair contractor if:
- The crack is more than 6 inches long
- There are many cracks
- The tub moves when you step in
- The crack is near the drain or faucet
- Water damage has already happened
In those cases, it might be better (and safer) to replace or professionally refinish the tub.
How to Prevent Future Cracks
Once you’ve fixed your tub, you’ll want to keep it that way.
- Don’t use abrasive cleaners
- Avoid dropping heavy items in the tub
- Don’t place sharp or hard things directly on the tub
- Add support underneath if your tub moves when you step in
- Reseal the edges of your tub every year or so
These habits can make your tub last years longer.
FAQs
Can bathtub cracks be repaired?
Yes. Most small and medium cracks can be repaired with a tub repair kit. These kits work best on acrylic and fiberglass tubs. If the crack is too big or deep, you may need a pro.
What is the best sealant for a cracked bathtub?
Use a two-part epoxy filler made for tubs. It works better than silicone and lasts longer. Always match it to your tub type whether it is acrylic or fiberglass.
Will Flex Seal fix a cracked bathtub?
No. Flex Seal is not made for tubs. It doesn’t stick well to smooth surfaces like acrylic or fiberglass. It may peel off or leak over time.
How do I tell if I have a fiberglass or acrylic tub?
Tap the surface. Acrylic sounds solid and warm. Fiberglass sounds hollow and cooler. You can also look underneath — fiberglass has strands, acrylic does not.
Summary
Fixing a cracked tub doesn’t have to be hard. If you take your time, follow each step, and use the right kit, your repair can last for years.
Just be sure to clean well, mix carefully, and give it time to dry. If the crack is too big or keeps coming back, don’t be afraid to call a pro.
Either way, now you know how to fix cracks in a bathtub and what to watch out for in the future.
