How to Clean a Fiberglass Tub and Shower

Fiberglass is a light, non-porous surface that is easy to scratch and dull if you use the wrong tools or harsh chemicals. This guide walks you through a safe, effective cleaning routine that removes soap scum, hard water spots, and mild mildew without damaging the gel coat. You will need only basic supplies you likely already have at home.

What You’ll Need

Liquid dish soap (grease-cutting kind)
White vinegar
Baking soda (optional, for stubborn spots)
Non-abrasive sponge or microfiber cloth (avoid scouring pads)
Soft-bristle brush (old toothbrush works for corners)
Spray bottle
Clean towels or a squeegee for drying

Step-by-Step

Rinse the surface with warm water. Use the showerhead or a bucket of warm water to wet the entire tub and shower walls. This loosens surface dirt and makes the cleaner more effective.
Apply a gentle cleaning solution. Mix equal parts white vinegar and warm water in a spray bottle, or use a few drops of dish soap in a bucket of warm water. Spray or wipe the solution over the fiberglass, working in small sections (about 2 square feet at a time) so it does not dry out.
Scrub with a soft sponge in circular motions. Use light to medium pressure. For corners, grout lines, or around fixtures, use a soft-bristle brush or an old toothbrush. Do not press hard—fiberglass scratches easily.
Let the cleaner sit for 5–10 minutes. This dwell time helps break down soap scum and hard water minerals. For tough stains, make a paste of baking soda and water, apply it to the stained area, and let it sit for 10 minutes before scrubbing gently.
Rinse thoroughly with warm water. Make sure no cleaner residue remains. Leftover soap or vinegar can leave a film or cause the surface to look dull. Use the showerhead to rinse from top to bottom.
Dry the surface with a clean towel or squeegee. Drying prevents water spots and mineral buildup. If you have a squeegee, use it after every shower to keep the fiberglass cleaner longer.
Buff with a dry microfiber cloth for shine. Once dry, a quick buff restores the original gloss and removes any remaining streaks.

Common Mistakes

Using abrasive scrubbers (steel wool, scouring pads, or stiff brushes) that scratch the gel coat and leave permanent dull marks.
Using harsh chemical cleaners like bleach, ammonia, or drain cleaners that can discolor or weaken fiberglass over time.
Letting cleaner dry on the surface—this leaves a sticky residue that attracts more dirt.
Skipping the rinse step—residue buildup dulls the finish and can cause irritation.
Scrubbing too hard—fiberglass is softer than tile; heavy pressure creates micro-scratches that trap grime.

Tips

Clean your fiberglass tub or shower every 1–2 weeks to prevent buildup. Regular maintenance is much easier than deep cleaning.
Use a daily spray (water and a drop of dish soap) after showers to keep soap scum at bay.
For hard water stains, soak a paper towel in vinegar and lay it on the stain for 15 minutes before scrubbing gently.
Never use colored cleaners or those with dyes—they can stain the fiberglass.
If you have a textured tub bottom (non-slip), use a soft brush to clean the texture without damaging it.

Troubleshooting

If the surface looks dull after cleaning: You likely have a residue film. Rinse again with warm water, then wipe with a 50/50 vinegar-water solution and rinse. Buff dry with a microfiber cloth.

If there are stubborn hard water rings: Make a paste of baking soda and water, apply it to the ring, and let it sit for 15 minutes. Gently scrub with a soft sponge, then rinse. Repeat if needed.

If you see scratches or scuffs: For minor scratches, use a specialized fiberglass polish or a fine automotive rubbing compound (test in an inconspicuous spot first). For deep scratches, you may need a fiberglass repair kit, but that is a bigger job.

If mildew appears in corners or caulk: Clean with a vinegar solution, then dry thoroughly. If mildew persists, the caulk may need to be replaced. Keep the area ventilated to prevent regrowth.

If the cleaner leaves a white film: This is often from hard water reacting with soap. Rinse with distilled water (if available) or use a vinegar rinse to dissolve the minerals.

Frequently Asked Questions

Can I use bleach on a fiberglass tub?

Bleach can discolor and weaken fiberglass, so it is best avoided. Use vinegar or a mild dish soap solution instead. If you must use bleach for disinfecting, dilute it heavily (1 part bleach to 10 parts water) and rinse immediately.

How do I remove yellow stains from a fiberglass tub?

Make a paste of baking soda and water, apply it to the yellowed area, and let it sit for 15–20 minutes. Gently scrub with a soft sponge, then rinse. For stubborn stains, use a fiberglass-specific cleaner.

Can I use a magic eraser on fiberglass?

Melamine foam (like a magic eraser) is slightly abrasive and can dull the finish. Use it sparingly and with light pressure, or skip it in favor of a soft sponge.

How often should I clean my fiberglass shower?

For best results, clean weekly or every other week. If you have hard water, you may need to clean more often and dry the surface after each use.

Is it safe to use a steam cleaner on fiberglass?

Steam cleaners can be used on fiberglass, but keep the nozzle moving and avoid high heat on one spot for too long, as it can damage the gel coat. Test in a small area first.

Why does my fiberglass tub look dull even after cleaning?

This is usually due to a buildup of soap scum or hard water minerals. Use a vinegar rinse and buff with a microfiber cloth. If it remains dull, the gel coat may be worn and need polishing.

Sources: American Cleaning Institute. Menus and buttons can differ slightly by version. Spotted something out of date? Tell us.