How To Remove Tough Stains From Fiberglass Tub?

White Vinegar and baking soda combination are best to remove tough stains from fiberglass tubs and clean them spot-free. It’s even the most inexpensive, worthwhile, and common technique of cleaning fiberglass without fading shine.  

However, several types of stains may appear on your fiberglass tub and shower. You should treat your tub stains based on their origin to get the maximum results with little effort. 

This post demonstrates easier, smarter, and faster methods of removing stains from a fiberglass tub. So each time you clean the tub, you’ll discover an elegant-looking tub. Let’s check out the methods. 

Table of Contents

How To Remove Stain From Fiberglass Tub

How To Remove Tough Stains From Fiberglass Tub

All the methods aren’t equally effective for all types of stains. So following one method is not a good idea, yet it may damage your tub. 

Rather, it’ll be great to follow the methods in its best situation to remove the stains from the deep.

Method 1: Removing Light Stains

Due to the regular use of soap and shampoo during your bathing time, a light layer of soap and shampoo scum or residue will build on the upper surface of the tub. White Vinegar and water are enough to remove these stains. 

Cleaning Process

  • Take 1 cup of white vinegar in a glass bowl and leave it in your microwave for 2 minutes to warm it. 
  • Remove the vinegar from the microwave and mix it with 1 cup of water. 
  • Pour the mixture into a spray bottle.
  • Take a towel and spray an adequate amount of prepared solution to saturate the towel.
  • Rest the towel on the stained tub area for 1-2 hours. 
  • Then, remove the towel and scrub the space with a soft sponge. 
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Rinse the tub with clean water, and you’ll find a white tub as it was before because many users find this solution to work nicely on 7 years aged bathtubs. 

Method 2: Removing Rust Stains

Is your tub old? Then there is a high chance you will find rust stains on the tub due to its metal fittings and fixtures. 

The microscopic metallic deposits will stay on the tub when the water runs. If the tub isn’t cleaned regularly, the deposits buildup creates rustic stains on the tub surface that looks yellow, brown, or red. 

Baking soda with vinegar exclusively cleans those stains. For tough rust stains, acetone or paint thinner is the best solution. But here we’ll talk about baking soda with vinegar, as it’s the organic solution. 

Cleaning Process

  • Mix half-cup of white Vinegar, half-cup of dawn dishwasher soap, and half-cup of baking soda in a glass bowl.
  • Once you add all of those ingredients, it starts to fizz. Wait a few seconds to remove the fuzziness. 
  • The consistency of the mixture will be gel-type paste. 
  • Apply the paste on the rust stains space of the tub with a putty knife. 
  • Wait 20 minutes after the paste application.
  • Scrub the tub to remove the stains from its deep. Use a little elbow grease on the hot spot of rust stains. 
  • Thoroughly rinse the tub and make it dry. 

Method 3: Removing Hard Water Stains

Hard water contains huge amounts of iron, calcium, and magnesium. On average, 3 to 2600 mg of calcium and magnesium is found per litter of hard water. 

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This is a red flag and creates disgusting hard water stains on the toilet bowl, tiles, and tubs. 

Borax, bleach, or phosphoric acid are good at removing hard water tough and stubborn stains from any surface, including fiberglass, acrylic, and ceramic tubs. 

Cleaning Process

  • Mix half-cup of the phosphoric acid and half-clean water into a spray bottle. 
  • Spray the solution on the toughest iron spots of your tub. 
  • Let the acid sit in the space for 20 minutes. During this time, the acid’s chemical reactions will soften the stains. 
  • Rinse the tub after scrubbing the space. 


  • Wear safety gear like hand gloves, full-sleeve clothes, and goggles before dealing with an acidic solution because anything can happen anytime, even if you are aware. In that case, safety is best. 
  • Never use Borax, bleach, or phosphoric acid alone in your tub, because fiberglass is a sensitive material. Using the acid may permanently fade its shine, scratch, or damage it. 

That’s all for home solutions. Now let’s look at some of the best but most affordable, non-toxic, and pet-safe multi-purpose store-bought cleaners. If you don’t have time to follow these homemade remedies, using them can be convenient for you. 

  • Mr. Clean Magic Sponges

Mr. Clean magic pads or sponges, whatever you say, is a multi-purpose cleaner that cleans any stains from all surfaces. You can use it to clean everything from messy kitchen countertops to greasy microwave ovens, fade shower glass to tough stains shower tub. 

It has No abrasive or harsh chemicals, and scrubs are 4x stronger than regular sponges. Wet, squeeze and rub are the 3 steps to use this cleaner pad and remove your fiberglass tub’s light to deep stains. 

  • TotalBoat White Knight Fiberglass Stain Remover
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TotalBoat stain remover is formulated to spot-clean the fiberglass boat, tub, shower, or furniture. This gel-type formula removes waterline, dirt, exhaust, or rust stains from the fiberglass gelcoat surface to rejuvenate its shine. 

To use this cleaner, apply the formula on the toughest and most stubborn stains and wait 10-15 minutes. Then scrub all the area of the tub and rinse it. Since it is non-abrasive, there is no risk of scratching your tub. 

Remove Tough Stains & Give Your Fiberglass Tub A Pristine Look

No matter whether you use home products or store-bought fiberglass cleaner to remove your tub’s tough stains, grime, and grease. Instead, it matters more whether you use the right cleaner for the right stains. 

So, before choosing the cleaning solution, try to identify the reasons for stains, their types, and how deep they are. The better your identification, the better you can sparklingly clean the tub. 

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