How to Fix a Crack in a Bathtub

Don’t worry if you find a crack in your bathtub. With the tips in this guide, I’ll walk you through how to fix a crack in a bathtub and prevent future damage.

Here’s the basic process: Evaluate the damage to your tub, thoroughly clean the area, apply a repair kit suitable for your tub’s material, do some sanding, and let it dry. While most small cracks can be fixed DIY, if it’s a large section or your bathtub’s structure is damaged, you should call in the pros.

If a crack isn’t the only thing making your bathtub an eyesore, consider returning it to its former glory by refinishing or reglazing it. Learn more about this process with our guides:

• What is Bathtub Reglazing?
• The Pros and Cons of Reglazing a Bathtub

Types of Bathtub Cracks

Before tackling any repairs, it’s essential to identify the type of crack in your bathtub:

• Hairline cracks: These are surface-level cracks that don’t go all the way through. They’re usually fixable at home.
• Stress cracks: These show up when something heavy hits the tub or if there’s too much weight in one spot. Some can be fixed at home, but others might need a pro.
• Structural cracks: These are the serious ones. If your tub is shifting or the crack is letting water through, you’ll need professional help.

Quick Test: Press gently on both sides of the crack. If it “spider-webs” or moves even a little, stop right there and contact a professional plumber. Also, try running your fingernail across it: If it catches deeply, that’s another sign you might need expert help.

The Heart of Your Repair Kit

The key to successfully repairing a crack in your bathtub is to determine your bathtub’s material before you buy anything. You need a compound that matches your tub’s material and color. Some kits can repair multiple types of tubs, but not all.

The most common bathtub materials include:

• Porcelain-enameled steel: Repairs typically require specialized enamel repair kits.
• Cast iron: Rare cracks can be fixed with metal-specific epoxy.
• Acrylic: Minor damage can often be repaired with acrylic repair kits.
• Fiberglass: Needs fiberglass repair kits and sometimes special tools.
• Cultured marble: Repairs often require professional expertise.

Pro Tip: Most tubs aren’t pure white. Look for kits that let you mix colors to match your tub perfectly.

Your DIY Repair Shopping List

Here’s a checklist of everything you’ll need. With these materials at hand, you’re ready to transform from a DIY novice to a bathtub repair pro.

Safety Gear

Chemicals used for bathtub repair can be dangerous. They can cause eye and skin irritation, dizziness, and breathing problems. Always wear appropriate safety gear.

• Respirator: A NIOSH-approved face mask (sometimes called a vapor respirator) that filters out dangerous chemical vapors — regular dust masks won’t protect you from harmful repair fumes.
• Safety gloves: Chemical-resistant ones that can handle epoxy. (Your kit may come with these.)
• Safety goggles: Full coverage to protect your eyes.
• Ventilation: A portable fan to keep air flowing and open windows if possible.
• Floor protection: Drop cloths or plastic sheeting.

Basic Tools and Materials

• Bathtub repair kit, which typically contains everything you need, including sandpaper, putty knife, and nitrile gloves.
• Cleaning supplies that have gentle, non-abrasive cleaning solutions to remove soap scum and buildup. Have trash bags handy.
• Microfiber cloth for thorough cleaning.
• Acetone or rubbing alcohol for surface preparation if your kit doesn’t have a primer.
• For fiberglass tubs: 1/4-inch drill bit to drill a small hole at each end of the crack, also known as a “stop-drill” hole; this helps relieve pressure and prevent further cracking.

Understanding Repair Kit Types

There are two main types of kits you’ll come across when repairing a tub:

• Epoxy-based kits: Common and versatile, creating durable waterproof repairs for most tub materials. Long-lasting but require precise mixing and color matching. Best for surface repairs, may need multiple layers for deeper cracks. We focused on the epoxy-based kits for this article.
• Foam repair kits: Newer option using expanding foam that fills cracks completely. Easy to apply but requires careful monitoring during expansion. Better for structural repairs than cosmetic fixes, as smooth finishing can be challenging.
• Eco-friendly option: Consider using low-VOC or no-VOC repair kits if you’re sensitive to chemical fumes or want a more environmentally-friendly option. These kits might take longer to cure but produce fewer harmful vapors during application.

How to Repair a Crack in a Bathtub Step-by-Step

Let’s dive into the step-by-step process of repairing your bathtub using an epoxy-based repair kit. (While foam repair kits are available, I will focus on the more common epoxy ones here.) 

I will walk you through each stage of the repair, from the initial assessment to the final touches. Follow these steps and your repair kit’s instructions carefully for the best results.

1. Evaluate the Damage

Assess the depth, size, and location of the crack. Use your fingernail or a thin probe to check the crack’s depth. Consider professional repair or refinishing if you find any of the following:

• Crack is longer than 6 inches 
• Deeper than the surface level
• Near plumbing fixtures
• Tub moves when pressure is applied
• Water damage found under the bathtub

2. Prepare the Area

Grab your gear and get the party started. The epoxy will work best if your bathroom is between 65 and 80 degrees F.

• Set up your fan to ensure good air flow to remove fumes and help the drying process. Turn on your bathroom’s exhaust fan, if available, for extra ventilation.
• Clean the damaged area thoroughly with rubbing alcohol or acetone to remove oils, soap scum, and debris. Doing this helps the repair compound stick better. 
• Let the area dry fully before you move on to the next step, which takes about 15 minutes.
• For fiberglass tubs only: Drill tiny holes at each end of the crack to stop it from spreading.
• Gently sand the area around the crack with the sandpaper included in your kit to prepare the surface. Be careful to not scratch the surrounding areas.

3. Prepare the Repair Compound

Read the instructions on how to mix your kit’s compound TWICE, as you generally get one shot at doing this right the first time.

• Mix only the amount you’ll use in 10 minutes.
• If your kit has two parts, be precise with your measuring.
• Do a test mix on cardboard first.

4. Apply the Repair Compound

Apply the compound with a plastic putty knife, ensuring it fully covers the crack. 

• For larger cracks, reinforce by covering the filled area with a piece of fiberglass cloth or similar compatible material.
• Smooth the compound out so it’s level with the tub surface.
• If needed, add a thin second layer of compound 
• Clean up any excess before it dries.

5. Allow Time to Cure

Let the repair compound cure completely. This typically takes 24 to 48 hours, but always refer to your product’s specific instructions for the expected wait time. 

• Ensure proper ventilation in the bathroom during this process to help the compound set and minimize odor.
• Don’t use the bathtub until it fully cures.
• Keep the fan running to improve airflow.

6. Final Steps

Once dry, sand the repaired area to a smooth finish. 

• Sand gently with the fine-grit paper included in your kit.
• If needed, apply a second coat for a seamless repair. 
• When sanding acrylic tubs, be especially careful to avoid damaging the surrounding surface.
• Apply a finish coat, if your kit includes one, and wait the necessary time, typically 24 hours.
• Test the repair by running water over it.

See Related: How to Reglaze a Tub

Here’s a quick video demonstration of how to repair a bathtub crack using an epoxy repair kit.

If you’re opting for a foam repair kit for your cracked bathtub, here’s a video to guide you through the steps.

When to Call a Pro

While DIY repairs can be effective for minor cracks, contact a local plumber for help if you’re not confident in repairing the crack yourself or if you notice the following:

• Cracks longer than 6 inches or deeper than surface level.
• Cracks near plumbing fixtures or drains.
• Multiple cracks or extensive damage across the tub.
• Structural cracks, which can be caused by underlying issues.

Prevent Future Damage

An ounce of prevention is worth a pound of the cure. Keep your bathtub and your bank account in tip-top shape with these tips:

• Use a non-slip mat to prevent cracks from dropped items.
• Clean your tub regularly with non-abrasive cleaners, especially on acrylic or fiberglass tubs.
• Address ventilation issues to prevent moisture-related damage.
• Consider professional care with an inspection and maintenance every few years.
• Be cautious with heavy objects near the tub to avoid impact damage.

Your Tub’s New Lease on Life

Small cracks in your bathtub can be repaired yourself when you have the right tools and materials. Grab your cleaning supplies, safety gear, and repair kit for your tub type, and you’ll be a DIY tub talent. 

Keep in mind this project requires attention to detail and handling hazardous chemicals, so don’t hesitate to reach out to a professional for help, especially if your tub has any major damage.

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Main Image Credit: Pavel / Adobe Stock Free

Raven Wisdom

Raven Wisdom is an experienced DIY enthusiast and writer based in West Texas. Her areas of focus include home remodeling and upgrades, outdoor projects, gardening, and sustainable living. Self-described as half-feral, but mostly harmless, Raven is also a devoted mother of two children in an Autism family, and an active supporter of local humanitarian efforts and animal rescues.

Posts by Raven Wisdom