5 ways to clean a fiberglass tub that has yellowed

Fiberglass tubs are popular bathroom fixtures as they are inexpensive and easy to install. Unfortunately, they are prone to several issues, among them staining.

The stains are mainly from hard water, with mineral deposits and soap scum causing the bathtub to appear yellowish.

Yellow stains can be hard to remove if left on for too long. However, a suitable chemical cleaner can remove these tough stains from your fiberglass tub and restore it to its original color.

You can also use inexpensive products such as baking soda, vinegar, hydrogen peroxide, and others to clean your bathtub.

Below, we have compiled various techniques you can use to clean your fiberglass tub. We have also included step-by-step cleaning instructions to make your bathtub look new again.

Top 5 ways to clean a yellowed fiberglass tub

These are some of the most effective methods of cleaning a stained fiberglass tub:

1. Chemical cleaners

Chemical cleaners are one of the best ways to get yellow stains out of fiberglass tubs. The cleaners are specifically designed to deal with tough stains and can make cleaning your bathtub an effortless experience.

However, not every commercial cleaner is ideal for use on a fiberglass tub, as some can be too abrasive.

The best types are usually mild but effective. They will remove the stains without causing any damage.

We recommend Weinman tub, tile, and fiberglass cleaner for cleaning a yellowed fiberglass bathtub.

If you can’t find it, use any of the following:

To clean your fiberglass tub using these (and any other ideal) chemical cleaners:

  • Apply them to the tub per the instructions.
  • Let the cleaner sit on the tub for a few minutes to penetrate the stains.
  • Scrub the tub with a non-abrasive sponge or soft brush
  • Rinse with water and let the tub dry

Note: you might have to scrub your tub a few times to eliminate some tough stains.

2. Baking soda

baking soda

Natural remedies are a great alternative if you dislike chemical cleaners. Baking soda is one of the best natural remedies to whiten a yellowed bathtub.

It is a highly effective stain remover that can eliminate tough yellow stains. It also helps to deodorize your tub drain.

To clean your fiberglass tub with baking soda:

  • Mix an equal amount of baking soda and water to create a thick paste.
  • Apply the paste to the bathtub placing extra attention on the areas with the stains
  • Squeeze lemon juice onto the baking soda paste and let the mixture sit for about 15 minutes.
  • Scrub the paste using a non-abrasive sponge or a nylon-bristle brush and rinse it with cool water.


You might find that some stubborn stains remain after cleaning. In this case, you can keep cleaning with the baking soda paste until you get all the yellow stains out of the fiberglass tub.

You can also apply the paste and leave it overnight to penetrate the stained areas of the tub completely.

3. White vinegar

Heinz White Vinegar

Vinegar is another excellent way to clean a stained fiberglass tub. It is a mild acid that works perfectly by dissolving yellow stains from hard water mineral deposits and soap scum.

To clean your fiberglass tub using vinegar:

  • Fill a spray bottle with white vinegar
  • Spray the vinegar all over the tub, making sure to cover the stained areas generously
  • Let it sit for about 20 to 30 minutes
  • Scrub the tub with a non-abrasive sponge or a soft brush
  • Rinse the with water, making sure to rinse off all the vinegar

You can keep cleaning with vinegar until all the yellow stains disappear. You can mix vinegar with baking soda for quicker results, creating a more powerful cleaning mixture that will work on stubborn stains.

4. Trisodium phosphate

Trisodium Phosphate

Trisodium phosphate is a chemical compound with several uses, including cleaning and removing stains. It is quite powerful, but diluting it provides a mild but effective solution for getting rid of tough stains.

To clean your fiberglass bathtub using the compound:

  • Dilute trisodium phosphate with warm water. Make sure it dissolves fully to avoid scratching the surface of the bathtub.
  • Apply the solution to the tub’s surface, covering all the areas.
  • Scrub with a soft sponge or brush
  • Rinse with cold water

When rinsing, remove all the residue, so it does not damage the bathtub.

5. Using hydrogen peroxide

Hydrogen peroxide

Hydrogen peroxide is another excellent cleaning agent you can use to make a fiberglass tub white again. It is an oxidizing agent that “bleaches” stains and will get rid of even the most challenging spots.

To clean stained fiberglass:

  • Lay white cloths on the surfaces of the tub
  • Pour hydrogen peroxide on the pieces of cloth until they are wet but do not let the hydrogen peroxide drip.
  • Leave them to sit overnight to remove all the stubborn stains.
  • Remove the pieces of cloth and rinse the tub using cool water, making sure to rinse off all the hydrogen peroxide.

You can keep repeating the process until all the yellow stains are gone.


Fiberglass bathtubs are affordable and attractive features for a bathroom. However, they can easily stain if neglected, turning to an unappealing yellowish color.

Fortunately, with the above cleaning methods, you can easily get rid of these stains, restoring your yellowed fiberglass tub to its original look.

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