How to repair an acrylic bathtub yourself

Why do acrylic bathtubs crack?

Before we move on to the main topic of the article, namely how to repair a cracked acrylic bathtub, it is worth explaining when this type of damage occurs. The most natural cause is simply the ageing of the bathtub. The passage of time affects not only people, but also the objects we use every day. Scratches are a natural consequence of intensive use – and it hardly needs to be said that a bathtub is subjected to considerable wear over the years, especially when it is used every day by four or more family members.

However, a cracked acrylic bathtub may also need to be repaired because of incorrect installation or because the bathtub has moved. Sometimes users fail to provide sufficient support for the bathtub, causing it to flex slightly whenever someone steps inside. Cracks may not appear immediately, but after some time they become visible to the naked eye.

Often, the cause is simply the properties of the material. Acrylic and fibreglass bathtubs are lightweight and affordable, but they are also more prone to cracking. Most acrylic bathtubs consist of a top layer of sanitary acrylic, usually 3–5 mm thick, and lower reinforcing layers made of fibreglass and polyester resin or another composite material. If these layers become damaged as a result of age or extreme stress, a crack can form.

Minor scratches and grooves: how to repair a scratched acrylic bathtub

If the crack is small and shallow and the bathtub is not leaking, you can repair it using a readily available acrylic repair kit. These kits usually contain two-part epoxy or acrylic filler, hardener and sandpaper.

Acrylic is a type of plastic, so in practice you are repairing a plastic bathtub. Here is how to do it in a few clear steps.

1. Clean and dry the damaged area

Start by preparing the surface. Wash the damaged area thoroughly with a mild cleaning product. Remove all soap residue, grease and limescale. Then wipe the area and allow it to dry completely. Moisture is the enemy of every type of filler.

2. Sand the area around the crack

Use the fine sandpaper included in the repair kit to lightly roughen the surface around the crack. This creates the ideal texture for the filler to bond properly with the acrylic. You can protect and define the surrounding area using masking tape.

3. Drill stop holes

For longer cracks, a step that may not seem intuitive is sometimes recommended. Use a drill with a very thin drill bit and make a tiny hole at each end of the crack. This relieves tension in the material and prevents the crack from spreading further under pressure. However, we would emphasise that this step should only be used for clearly visible and longer cracks.

4. Apply the epoxy mixture

What should you use to repair an acrylic bathtub? Naturally, filler. Mix the repair compound with the hardener exactly according to the manufacturer’s instructions. Use a spatula to press the mixture deep into the crack. Smooth the surface so that the filler sits slightly above the surrounding area, but without creating an excessively thick layer.

5. Allow it to cure and sand it smooth

Now you need to be patient. Leave the filler to cure for as long as the manufacturer recommends, often several hours and ideally overnight. Once the compound has hardened, use wet-and-dry sandpaper and sand the repaired area in circular motions until it is completely level with the surface of the bathtub. Finally, apply polishing paste or touch-up lacquer to restore a perfect shine.

When should you repair the bathtub, and when is it time to buy a new one?

Sometimes investing time and money in a repair only delays the inevitable. The following table will help you decide whether repair or replacement is the better option.

Situation in the bathroom	Recommended solution	Why is this the best option?
Minor scratches and superficial grooves.	DIY repair (acrylic repair kit)	This is only a cosmetic defect. The repair filler seals the damaged area, and the bathtub can look like new again at a fraction of the cost.
The crack passes through the entire material and water is leaking beneath the bathtub.	Professional repair or replacement	Do not risk structural damage to your home. If the bathtub is older, investing in a plumber may not be worthwhile and buying a new bathtub may be the better option.
The bathtub visibly flexes under your weight and the cracks keep returning.	Complete replacement + reinforcement of the base	The problem lies in the support beneath the bathtub. No filler can permanently hold together material that is constantly moving. The new bathtub must be properly supported or installed.
The bathtub is more than 20 years old, yellowed and covered in scratches.	Complete replacement	Old acrylic loses its properties and becomes brittle. Repairing one area may simply allow another crack to appear elsewhere.

Do you have older people or lively children at home? Cracked acrylic can form dangerously sharp edges. If there is a risk of cuts, do not delay the repair or replacement even for a single day.

Prevention: how to keep acrylic in perfect condition

If you want to avoid future repairs altogether, simply follow a few basic maintenance rules.

1. Avoid aggressive chemicals and harsh cleaning: Never use abrasive cleaning powders, wire wool or aggressive cleaning products containing alcohol or acids on acrylic. They can dull the surface, create microscopic scratches and make the material brittle. Use liquid soaps and soft cloths instead.
2. Be careful with heavy objects: Handle cosmetic bottles and the hand shower carefully above the bathtub.
3. Avoid overloading shower trays: Shower trays are designed for the standard load of one person. Long-term exposure to extreme pressure, for example when used by two people at the same time, can reduce the lifespan of the material.

Frequently asked questions

Why did the crack in my bathtub reappear after a successful repair?

You most likely did not remove the underlying cause of the problem. If the bathtub is poorly secured and flexes under a person’s weight, the repaired area will sooner or later fail again under pressure. A repair kit addresses the consequence, not the cause – which in this case is insufficient support beneath the bathtub.

Are some bathtub materials easier to repair than others?

Yes. Acrylic and fibreglass are the most suitable materials for DIY repairs because epoxy resins and fillers adhere to them very well. By contrast, cast-iron or enamelled bathtubs rarely crack, but if the enamel chips and corrosion begins, the repair requires highly specialised work by a professional.

Can an unrepaired crack affect an insurance claim in the event of water damage?

Very likely, yes. If an insurance company finds during its inspection that water had been leaking for a long time because of a visible and neglected crack, it may classify the incident as gross neglect of maintenance and reduce or completely reject the insurance payout. Carrying out the repair in good time is therefore worthwhile for your own peace of mind as well.