How to Remove Tough Stains From a Fiberglass Tub (Without Damage)

Updated May 5, 2022
Woman Cleaning Fiberglass Tub

Just the thought of cleaning your tub can make your back hurt. However, cleaning your fiberglass tub doesn't have to be tough. Learn how to remove tough stains from fiberglass tubs with ease. Get clear instructions on how to remove rust and hard water stains from your tub.

How to Remove Tough Stains From Fiberglass Tub

Lots of homes have fiberglass tubs. Why? Because they are light and affordable. However, when it comes to cleaning fiberglass tubs and sinks, you need a specific set of tools. To get you started, grab:

Vinegar and baking soda
  • Baking soda
  • Dawn dish soap
  • White vinegar
  • Hydrogen peroxide
  • Borax
  • Lemon juice
  • Commercial rust remover (CLR, etc.)
  • Spray bottle
  • Microfiber cloth
  • Old toothbrush/soft bristle brush
  • Cup

How to Clean Fiberglass Tub With Baking Soda and Vinegar

One of the easiest ways to weekly clean a dirty tub is using baking soda and vinegar. Whether you have mildew, stains, soap scum, or just need a good weekly cleaning, this method can quickly and easily wipe it all out.

  1. Wet the entire tub. (So, the baking soda sticks.)
  2. Sprinkle the tub with baking soda.
  3. Let that sit for a minute while creating a 1:1 solution of water and white vinegar in a spray bottle.
  4. Spray the baking soda with the mixture.
  5. Get the baking soda good and saturated.
  6. After it stops fizzing, spread the mixture over every area of the tub using circular motions with a cloth.
  7. Allow it to sit for 30 minutes. Longer if the stains are horribly built up.
  8. Scrub a bit more to remove any loose junk.
  9. Fill a cup with water and rinse the tub.

Remove Tough Stains From Fiberglass Tub With Textured Bottom

If you have tough stains on the textured bottom of your tub, don't despair. There is a quick fix for that.

Women preparing a natural non-chemical cleaner at home with baking soda and vinegar and lemon
  1. Create a thickish paste of baking soda and hydrogen peroxide.
  2. Add a few drops of Dawn dish soap.
  3. Spread the paste onto the bottom of the tub.
  4. Let it sit for 30 or so minutes.
  5. Use a bristle brush or toothbrush and scrub in circular motions.
  6. The dirtier the texture is, the more elbow grease you need to add.
  7. Use the cup to rinse.

Vanquishing Hard Water Stains From Fiberglass Tub

Hard water stains on the sides of your tub and bottom can be difficult to clean. However, they are far from impossible. For hard water stains, grab a lemon or two and some borax.

  1. Wet the tub.
  2. Sprinkle the hard water stains with borax.
  3. Cut the lemons in half.
  4. Rub the lemon over the borax.
  5. Let it sit for an hour or two.
  6. Rinse with water.
  7. If any stain remains, sprinkle baking soda on a wet toothbrush.
  8. Add a drop of Dawn and scrub.

How to Remove Rust Stains From Fiberglass Tub

If borax, lemon, and white vinegar aren't working to get rid of the hard water and rust, you need to look for a commercial rust remover. These come by several names, but any rust and limescale remover safe for fiberglass works.

Packet of detergent powder with borax
  1. Add the recommended amount of the commercial cleaner to the tub, per the instructions.
  2. Allow it to sit for the recommended amount of time.
  3. Rinse and dry.

Since commercial rust removers can hurt the skin, it's important to glove up before using them.

How to Clean Mold and Bathmat Stains From Fiberglass Tub

Do you have mold on your fiberglass tub? You aren't alone. To get rid of mold or bathmat stains, you need a bit of baking soda and vinegar.

  1. Create a paste of baking soda and water.
  2. Smear the paste on the mold.
  3. Soak a towel in straight vinegar.
  4. Put the towel over the paste.
  5. Allow it to sit for at least an hour.
  6. Scrub until all the mold or bathmat stains are gone.
  7. Rinse with water.
  8. Wipe with a cloth.

Best Commercial Cleaner for Fiberglass Tubs

If home remedies aren't really your thing, you can turn to commercial cleaners. However, you want to ensure you choose a cleaner designed for fiberglass tubs. Why? Because you don't want to be so abrasive that it damages the fiberglass. A few cleaners to try for fiberglass include:

While these cleaners are designed specifically for fiberglass, you want to watch using them on damaged tubs. You also want to make sure you are following the directions fully and wearing appropriate protective gear like gloves.

Prevention and General Cleaning Don'ts for Fiberglass

Fiberglass tubs and sinks are pretty versatile. However, you can do a few things to prevent soap scum and rust from forming. Additionally, a few cleaners should avoided. See this list to get all the details.

  • After showering or bathing, wipe down the tub with your towel. This can help to avoid rust and soap scum build-up, especially for those with hard water.
  • Always wear the proper protective equipment--like gloves and old clothes--when using chemicals for cleaning.
  • To avoid scratching fiberglass, watch out when using steel wool or abrasive cleaners.
  • Avoid using hydrogen peroxide on any colored fiberglass since it can fade it.
  • Make sure to rinse chemicals well.

Refinishing Fiberglass Tubs

If you have a tough stain you can't touch, it might be more than a stain. Sometimes the finish on a fiberglass tub gets damaged. When this happens, stains penetrate into the fiberglass and are nearly impossible to remove. In this instance, you might need to see a professional about refinishing your tub or consider getting a new tub.

Clean the Tough Stains off Fiberglass Tubs With Ease

Fiberglass tubs are durable. That makes them easy to clean. However, it's important to pay attention to the dos and don'ts of cleaning fiberglass to make sure you don't give yourself more work in the long run.

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How to Remove Tough Stains From a Fiberglass Tub (Without Damage)