What Will Clean a Fiberglass Bathtub With Set-in Hard Water Stains?

Fiberglass bathtubs are durable and attractive, but they often become stained easily. Hard water stains form on the tubs due to a buildup of minerals such as calcium and magnesium. These mineral deposits make the bathtubs appear unattractive and dirty. Removing the stains when you notice them will prevent the deposits from building up and becoming more difficult to remove later. Remove the hard water stains from the fiberglass bathtub with items that you have around your home or commercial cleaners.

...
Keep your fiberglass bathtub in good condition by cleaning it weekly.

Baking Soda Paste

Baking soda acts as a natural abrasive that will not harm the surface of the fiberglass. Combine an equal amount of baking soda with water or white vinegar to create a thick paste. Apply the paste to the bathtub while it remains wet by gently rubbing it over the hard water stain. After you apply the paste, let it sit for 10 to 15 minutes and then wipe it off with a soft sponge or a nylon brush. Repeat applying the paste until you remove the stains. Leave the paste sitting on stubborn stains overnight.

White Distilled Vinegar

Vinegar breaks down mineral deposits so that you can wipe them away easily. Soak paper towels in white distilled vinegar and place them directly onto the hard water stains. Once you apply the paper towels, allow them to sit for up to 30 minutes. Rinse the bathtub with cool water to remove any traces of vinegar. Scrub on the stains with a nonabrasive sponge and liquid dishwashing soap until you remove them completely.

Commercial Cleaners

Purchase commercial products to remove hard water stains and to keep your fiberglass bathtub clean. Always read the label on the products to determine if they work for removing hard water stains. Household all-purpose cleaners, bathroom cleaners and soft scrub products are effective at removing stains. Always read the directions on commercial cleaning products before applying them because not all products are formulated to work on fiberglass. Always test cleaning products in a small and inconspicuous area on the bathtub to prevent ruining the surface.

Tips and Warnings

Never use harsh abrasive cleaners to remove hard water stains from fiberglass bathtubs. These cleaners dull the finish of the fiberglass and can even scratch the surface. Nonabrasive sponges and soft-bristled toothbrushes work best for removing hard water stains because they will not scratch the fiberglass. Always dry the tub after each use to help prevent hard water stains. Once you finish cleaning the tub, polish it with an automotive whitening polish and a clean and soft cloth.