Plastic bathtubs have grown in popularity over the recent past. Compared to tubs made from other materials such as fiberglass, ceramic, or porcelain-enameled steel, plastic offers a less expensive alternative that is also easy to install. However, one of the common problems with plastic bathtubs is crack formation, particularly on the surface.

Because plastic is a crack-prone material, it’s vital to arrest any cracks to optimize durability while also minimizing the frequency and costs of replacement. In this article, I’ll discuss all the steps in great detail to help you through the process. I’ll also share some precautionary measures you can take to minimize the chances of damage and crack formation.

1. Clean Your Tub Thoroughly and Allow Ample Drying Time

The first step is to clean your plastic tub thoroughly using a non-abrasive detergent. I recommend using soap and warm water to clean your tub to minimize abrasion. Cleaning makes it easy to identify any cracks or dents on your tab, which may otherwise be concealed by dirt or debris.

Additionally, cleaning your tub, especially the damaged areas, ensures that you remove all debris and dirt, which may prevent bonding with the patch material. Make sure you allow ample time for your tub to dry.

2. Locate Cracks and Mark Them for Easy Identification

Once you’ve located the cracks, make clear markings to make them easy to identify. This will ensure that you minimize the time spent finding them after you have prepared your patch material, making the repair process quick and easy.

3. Drill Quarter-Inch Holes on Either Side of the Crack(s)

After locating and marking the cracked areas, drill quarter-inch (0.64 cm) holes on both sides of the cracks. These holes will arrest the cracks and prevent them from extending.

Take extra precautions to clean and dry each of these holes. If there’s more than one crack on your tab, drill these holes on either side of each crack.

4. Sand the Marked Area Gently Using Sandpaper

Sand the area(s) around the crack with sandpaper. This is an essential step for two main reasons:

  • Sanding these marked areas helps eliminate any stubborn debris you may have missed during the initial cleaning.
  • Sanding the area adjacent to the crack will also help the patch material seal better and securely.

5. Prepare the Patch Material and Fill in the Cracks

After you’ve cleaned, dried, and sanded the cracked area, the next step is to fill the cracks with patch material. There are different materials you can use to fill in these cracks. I recommend using a fiberglass epoxy resin, as this will provide a lasting solution and minimize further damage in the future.

Make sure you fill the cracked areas and the holes you drilled earlier with this patching material. For best results, use a plastic applicator to fill in the cracks.

6. Remove Excess Resin Using a Putty Knife

Naturally, applying the filler material to the cracked surface won’t leave a smooth surface. To eliminate any coarse areas on the tub, use a putty knife to scrape off and remove excess resin from your tub.

Do this gently because you do not want to damage any other part of the tub with the putty knife.

7. Let the Filler Material Cure for a Minimum of 12 Hours

Curing is a process through which the filler material hardens. Although you can elect to purchase a curing agent to accelerate this process, leaving the resin material for 12 hours to 24 hours will allow the patch material to dry and harden.

8. Sand the Cured Area With Sandpaper for Smoothing

The process of removing the excess resin material isn’t sufficient to provide optimal smoothness. If you leave it as is, the dried resin can hurt you, or it can chip away, leaving the cracked area at risk of further damage.

Use soft grit sandpaper to smoothen the cured area to resolve this. Do this gently to avoid causing ugly marks on your tub. Repeat until the surface of your tub meets your desired outcome.

9. Clean the Sanded Area Carefully With a Wet Towel or Rag

Rinse a soft towel or rag to clean the cured area and remove any excess debris or plastic dust. This not only eliminates traces of the sanded surface, but also removes any traces of grease or grime. Take keen attention to do this gently to avoid damage, yet thoroughly to ensure a smooth finish.

10. Add a Thin Layer of Enamel Finish and Leave to Dry

To give your tub that glossy look, you can add a thin layer of gel coat enamel finish. Alternatively, you can also apply a sealer to prevent moisture seepage.

Because it can be difficult to select an effective product due to the numerous products in the market, I recommend trying this Gelcoat Tub and Shower Repair Kit (available on Amazon). Used by professionals, this repair kit works for scratches, nicks, and gouges in a variety of materials, including porcelain, ceramic, resin stone, and yes, plastic. It dries quickly and the surface is safe for use immediately after repair.

You might also want to read: Can You Paint a Plastic Bathtub?

Common Causes of Cracks in Plastic Bathtubs

Plastic is a less sturdy material when compared to other bathtub-making materials. Therefore, it’s difficult – if not impossible – to entirely eliminate the risk of cracks. It’s important to watch out for a few factors to avoid spending hundreds, if not thousands, in repair costs.

Here are the most common factors that cause cracks in plastic tubs:

Using Abrasive Cleaners

Plastic is very susceptible to abrasive detergents and cleaners such as bleach. Using abrasive cleaners can erode or undermine the structural integrity of your tub.

Accordingly, these strong detergents and cleaners can also wear down the gloss of the tub finish, resulting in moisture seepage into the material. This seepage will eventually cause the tub material to crack.

On that note, I recommend staying away from strong detergents and cleaners when doing maintenance work on your plastic bathtub. Opt instead for gentler alternatives to extend your tub’s life such as Better Life Natural Tub and Tile Cleaner, available on Amazon. The cleaning agents are plant-based for a natural, powerful clean that leaves surfaces sparkling and bright.

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On the same note, it’s equally as important to also use non-abrasive scrubbers to clean your tub, because these too can easily damage the plastic surface. Products such as the Qaestfy Shower Scrubber Cleaning Brush is specifically designed to be gentle on your tub while also being effective at removing dirt.

Lack of Proper Support

The tub repair experts at Surface Repair Service explain that one of the most common causes of cracks is the lack of proper support. Therefore, when installing a new tub in your space, I recommend ensuring that your tub arrives with all the appropriate supports and that these are correctly set up.

Your tub will gradually become deformed over time, resulting in crack formation if you don’t put the necessary support structures in place.

Dropping Objects In Your Tub

Most bathtubs are weight tested to support most people, yet these tubs do have a weight limit. As such, placing heavy objects or dropping heavy objects in your plastic tub is likely to cause cracking. 

These heavy objects can also result in dent formation, which can become cracks over time. Therefore, take plenty of care not to drop or place any heavy objects on your plastic tub.

Interestingly, even lighter objects such as shampoo bottles can cause cracks and dents. As explained by Surface Repair Service, while it’s common to drop objects such as bottles in your tub during cleaning, you should take care not to do this regularly.

The same applies to throwing objects at your tub. However small, these objects may cause cracks, chips, or dents that can be expensive to repair.

General Lack of Maintenance and Care

Sometimes, your tub’s length of service will depend on how you handle it. By keeping the above damage-prone factors within check, you can help keep the repairman at bay and enjoy service for years to come.

Remember, when adequately managed and with timely intervention, you can stop these small cracks from becoming larger cracks that warrant professional intervention.

Final Thoughts

Cracking is a common problem for plastic bathtubs. However, if the damage isn’t advanced, you can follow these guidelines and repair your tub, and in the process, save yourself some time and money. One of the crucial things to remember is that you have to arrest this damage before it becomes advanced and the cracks grow in size.

If the cracks are too big, I recommend contacting an expert because this will provide the best course of action to repair your tub. Trying to fix the tub yourself when the damage is extensive may result in even more costly damage.

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