Removing Hard Water Stains from Fiberglass

by April Reinhardt
(last updated August 15, 2016)


We have hard water in our neighborhood. The house we moved from four years ago was in the same neighborhood, yet we used a water softener to contend with the hard water deposits left behind, such as calcium, magnesium, limestone, and chalk. This house has no water softener, so we have a water filter for our drinking water, but that doesn't help the situation with our fiberglass bathtubs, shower stall, and basins.

While writing this article, I had to fetch some Tylenol and noticed the buildup of lime around the water fixtures of the tub. I made a mental note to clean the bathroom today. Through the years, I've found tried-and-true methods to rid the hard water debris, and I'll share those with you now:

  • Believe it or not, WD-40 works wonderfully to remove hard water debris from fiberglass. Spray it liberally anywhere you see the buildup, allow it to sit for about five minutes, and then use a non-abrasive sponge or pad to wipe it away. WD-40 also works wonders on glass shower doors for removing water stains.
  • Mix a paste of equal parts of baking soda and white toothpaste. Use a soft sponge to apply the paste to the hard water buildup and allow it to sit for about five minutes. With a clean sponge, sponge away the solution and rinse with clear water.
  • Although you should never use acidic materials full-strength on fiberglass, as it will etch the material, you can use diluted versions to clean away hard water deposits. In a plastic spray bottle, combine one-half cup of white distilled vinegar with one cup of hot water. Spray (or pour) the entire contents onto the hard water buildup and allow it to sit for at least three hours, and then rinse away.
  • To completely clean away hard water debris, you must use a product that deactivates or separates the minerals. Visit the cleaning isle of your local grocery store and read the labels of products specially formulated to get rid of hard water stains on fiberglass, and then give them a try.

Remember that harsh chemicals will etch the surface of fiberglass, so be sure to read labels of cleaning products to make sure that they are safe for use on fiberglass.

Author Bio

April Reinhardt

An admin­istrator for a mutual fund man­age­ment firm, April deals with the writ­ten word daily. She loves to write and plans to author a memoir in the near future. April attend­ed More­head State Uni­ver­sity to pursue a BA degree in Ele­men­tary Edu­ca­tion. ...


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What is four less than 8?

2016-12-30 05:49:58

Chris Martin

We have horrible we'll water,my acrylic tub had hard water build up and is hard to remove . Any new techniques to removing the stains will be appreciated.


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