Will Flex Seal fix a Cracked Bathtub? – What You Need to Know

will flex seal fix a cracked bathtub

Flex Seal is a proud product of Swift Response, LLC and has been one of the most innovative products for many homes across the US. These rubber-mixed sealants are versatile products that can be used to fix fractures, cracks or patches on many surfaces like wood, concrete, metals, fabric and plastic. Sometimes you may have encountered a situation wanting to use Flex Seal on your shower areas. Will flex seal fix a cracked bathtub? Does this go under Flex Seal’s capacity? We will clarify these questions through this article. 

Can You Fix a Hairline Crack on a Bathtub?

Cracks in a bathtub are the worst scenario we all fear about. Fibreglass made tubs tend to fracture at a high percentage compared to other materials. If the cracks are unseen or not treated at the beginning, they may continue to be hairline cracks over time. Water leakage could happen in this kind of situation, and the case needs an urgent repair if the leaking bathtub is not on the ground floor as it may leak water to the floor below. 

Hairline cracks which occur with constant usage and less care on the material could be treated in the first stages. If you identify a hairline fracture, you must make the preparations to repair it ASAP before it makes a huge crack, irreversibly dividing the surface. 

An untreated crack in the bathtub will cause to damage the flooring too. Especially if the floor is wooden, the wood will start to rot, and various insects like termites will find it a flourishing area to dwell in. On the other hand, various mould will grow underneath the supporting material and eventually will increase the degrading of the flooring. 

Can I Use Flex Seal on Bathtub?

Flex Seal is a sealing rubber compound used on many surfaces. When it comes to the bathtub fixing, it is also a “Yes.” You can use Flex Seal as an efficient sealant in fibreglass bathtubs. But the use of Flex Seal in porcelain and ceramic bathtubs does not provide a long-lasting superior bond. In such cases, you must replace the Flex Seal patch with a permanent solution within a few days. Although this polyurethane rubber layer interacts well with a fibreglass surface, it is crucial to know that this is a temporary treatment. Do not rely on the Flex Seal fixture over months. Go for a permanent remedy soon as possible. 

Will Flex Seal Fix a Cracked Bathtub?

Flex Seal is the best solution for a cracked bathtub. But you must be aware that this cure is provisional. You must arrange a permanent fixing later on within few days. If your tub is made of a material other than fibreglass, you will need to hurry. Because on surfaces like porcelain, ceramic, and cultured marble, the bond created by the rubber spray tends to loosen within a couple of days. After the temporary layer created by the Flex Seal, you are free to use the bathtub. Flex Seal liquid can resist a temperature range of -62.2°C to 176.6°C. Therefore, you can fill your tub with hot water. 

There are simple tips that you need to know before doing a crack treatment in your bathtub with Flex Seal. First, with a cloth, wipe all the water and moisture. Flex Seal manufacturers have suggested that it would be better if you could make the area dry with no moisture before applying Flex Seal because a wet surface will lead to poor bonding.

Once you are sure that the surface is completely dry, you can proceed with the project. Then you can use Flex Tape and cover the cracked area. This is to provide a stronger bond. Once you are done with the taping, you can rest it for about 10 minutes and start spraying Flex Seal liquid. It is required to cover the surrounding of the crack too. And, it will give your bathtub a large visible patch but covering excess area is essential to create a reliable fixing. 

It is recommended to use more layers of the sealant for better protection and waterproof quality. But you will have to wait 24 hours before the next coat. Once you have finished the patching, again, there must be a resting period of 48 hours before filling the bathtub with water. 

Is Flex Seal a Permanent Solution for Cracks?

It is clearly mentioned on the manufacturer’s official website that Flex Seal is not a permanent sealing. Therefore, if you use it to treat a crack as an immediate solution, you cannot expect it to last longer. 

What Else Can You Use to Seal a Cracked Bathtub?

Cracked bathtubs can be treated with spray foam. This is called foam insulation. These are suitable to use even under bathtubs. If you do not have enough skills, you will have to hire a plumber for this insulation process. You will have to spend about $ 0.44 – $ 0.65 per board foot. 

If your bathtub is metallic, the cracks can be repaired by welding. This is not a DIY; therefore, go must get the assistance of a skilled technician.

An epoxy resin or a fibreglass resin that costs $2- $5 per square foot is another treatment you can use to stop the leakage of a cracked bathtub. You will have to hire a professional as it is a project needing experience.  

Bathtub repair kits are also an effective way of fixing cracked areas. You can purchase such a kit from hardware or an online store and do it yourself. There will be two mixtures that you need to be applied separately with adequate time intervals. Once you read the product instructions, you will be able to do it easily. The kit cost will be between $10 and $40. 


Flex Seal can act as a good remedy for a cracked bathtub. But it does not provide a permanent result. If you need to get a clear idea about the method of application, please refer to the above passages. 

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