Repairing an Acrylic or Fiberglass Shower Using a Filler Kit

Feet in bathtub with shower on
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Fiberglass or acrylic bathtubs and showers are easy to install and are often less expensive than other options, such as a cast-iron tub or ceramic tile shower stall, making them a favorite for budget-conscious homeowners.  Over time, though, the acrylic or fiberglass surfaces can get dented or cracked, often because of flexing of the walls of the fixture over time. Sharp blows can also dent, crack, or punch holes in fiberglass or acrylic. A variety of options are available at this point, including wholesale replacement of the bathtub or shower, or installing a new liner inside the old tub or shower.

But one fix that is much more cost-effective is to fill the crack or hole using a fiberglass/acrylic repair kit. These materials include epoxy-like materials similar to the compounds used as filler in automobile body repairs. In fact, some people use these automotive body fillers to make repairs on tubs and showers, or even sinks and toilets.

Acrylic/Fiberglass Repair Kits

Rather than using automotive body filler, though, a better choice is to buy a repair kit that is factory-matched to your tub or shower. These kits have filler paste already tinted to match the color of your fixture, and will include much of what you need to make the repairs—only a few extra tools and materials are required. A single kit may provide enough material to make several repairs. One manufacturer of fiberglass/acrylic repair kits (but not the only one) is Multitech Products, who makes many of the official repair kits sold by the plumbing fixture manufacturers themselves.

There are many repair and resurfacing products available, so make your choice carefully. For simple cosmetic repairs, most people find that a paste-type fiberglass/acrylic kit is easier to use than a spray product. Paste kits may include: 

  • Base coat paste and catalyst
  • Lightening and darkening toners
  • Rubbing compound or buffing bar
  • Wet/dry sandpapers

Some types of products also include a clear top coat that is sprayed or brushed on.

You Will Need

  •  Acrylic/fiberglass paste-type repair kit, color-matched to your fixture
  • Utility knife
  • Power drill with small drum sander or grinding disks
  • Wet/dry sandpapers (220-, 320-, 400-, and 600-grit)
  • Nail polish remover or acetate
  • Clean cloths or paper towels
  • Heat gun
  • Buffing bonnet 
  • Protective gloves
  • Ventilator mask

Caution: This repair uses an epoxy-type filler that has fumes that are hazardous. Good ventilation is required, as well as the use of an approved ventilator mask. Always follow the kit manufacturer's recommendations for safety measures. 

How to Use a Paste-Type Acrylic/Fiberglass Repair Kit

  1. Use a sharp utility knife to carve out a V shape around the edges of the damaged area. Make sure to cut down through the color layer of the acrylic or fiberglass into the structure below. Usually, this means cutting down between 1/16 and 1/4 inch. If the surface is very hard or the damaged area is very large, a sanding drum or grinding disk attached to a drill or Dremel tool will make this preparation easier. Angle the sides of the damaged area so that the filler paste can be applied smoothly. 
  2. Wipe the surfaces clean with cloths or paper towels, then use 220-grit sandpaper to slightly roughen the entire repair area. This slight roughening will help the paste adhere to the damage area. 
  3. Clean the repair area with nail polish remover or acetate. At this point, make sure to ventilate the area well and use a ventilator mask. Wear protective gloves for the following steps. 
  4. Transfer a small amount of paste filler from the kit into one of the provided mixing cups. If necessary, use the lightening or darkening toners to adjust the color to match your tub or shower (this is most often necessary with white tubs or showers). 
  1. Add the catalyst agent to the paste in the ratio recommended by the manufacturer. Mix the ingredients together thoroughly to form the activated filler paste.
  2. Apply the activated paste mixture to the repair area using the mixing stick provided in the kit. Make sure to fully fill the damaged area. Overfill the patch area slightly; it will be sanded flush later. 
  3. Allow the paste to fully harden for one hour, or according to the kit instructions. A heat gun can be used to speed up this drying time.
  4. Use wet/dry sandpaper to blend in the repair area with the surrounding surface. The best results are achieved if you sand in several stages using progressively finer grits of wet/dry sandpaper. Begin with 220-grit, then proceed by sanding with 320-, 400-, and finally 600-grit sandpaper. As you sand, drip water onto the sanding area with a wet rag to lubricate the surfaces.
  5. Clean away the sanding dust, then use the rubbing compound included in the kit to polish and blend the repair area with the surrounding material. High-speed buffing will give the best results—a buffing bonnet mounted to a drill or an automotive buffing tool is a good choice. 
  1. If your kit includes a clear top-coat layer, apply it now, according to kit instructions. 

Done patiently and according to instructions, the repair to your fiberglass or acrylic tub or shower should be nearly impossible to distinguish from the rest of the fixture.