How to Clean a Stained Fiberglass Tub

Stains on fiberglass tubs don't last long if you use the right cleaners. Even caked-on iron and rust stains can be removed with a little effort. Apply your chosen cleaners to fiberglass tubs using a soft sponge, a nylon, polyester or polyethylene brush with soft bristles, or a soft cloth. Do not use abrasive cleansers, steel wool, abrasive scrubbers or scrapers on the fiberglass tub or shower surround, as these can scratch the fiberglass.

Options for fiberglass stain removal include:

  • Liquid dishwashing degreasers
  • Liquid laundry detergent
  • Trisodium phosphate diluted in warm water
  • Baking soda and warm water paste
  • Homemade or commercial soft-scrub products

Homemade Cleaning Options

Combine the ingredients in a gallon bucket: 2 tablespoons of white vinegar, 1/2 cup warm water, 1 2/3 cups of baking soda and 1/2 cup of a liquid degreasing dish detergent. Apply the homemade solution directly to the stain and let it sit for an hour before rinsing and wiping clean.

A vinegar-and-baking soda paste applied to stained areas creates a chemical reaction that can remove the stain through the fizzing action generated by mixing backing soda with vinegar. Apply the vinegar and baking soda paste directly to the stained area and let sit for 15 to 20 minutes before rinsing and removal.

Stain Removal

An effective homemade stain removal includes wetting the stained area and patting it with baking soda. Squeeze lemon juice from a 1/4 slice of lemon directly onto the baking soda. Let the lemon juice and baking soda sit on the stain for at least 15 minutes before scrubbing with a nylon-bristle brush and rinsing clean.

To make a homemade soft scrub to remove black spots, grease or scuff marks from fiberglass tubs, combine 1/2 cup of baking soda, 1/2 cup of liquid grease-cutting dish detergent and 5 to 10 drops of lavender oil -- or your favorite fragrance -- in a bowl. Add the essential oil to the ingredients after mixing the baking soda and dish detergent thoroughly. Dip a sponge in the solution and apply to the marks in the tub until they are gone. Rinse and wipe dry.

Homemade Soap Scum Remover

Add 12 ounces of your favorite liquid degreasing dishwashing detergent along with 12 ounces of white distilled vinegar to a 1-quart spray bottle. Spray the tub and surround with the homemade soap-scum product and let it sit for up to an hour before rinsing and wiping clean. You can also use this solution to shine the tub after stain removal.

Best Practices

After stain removal, clean the entire tub area with a 1-to-1 ratio of ammonia and water to ensure no residue remains from the chosen stain remover. Rinse the tub with warm water, and then apply the ammonia-and-water cleaning solution to give the tub a polished sheen.