Cleaning a Fiberglass Tub

I have a fiberglass bathtub with the walls and shelves attached. I can't seem to get black mold spots out of the grout attaching the tub to the walls no matter how hard I scrub. Do I have to re-do the grout? Any advice regarding effective store-bought or homemade fiberglass-safe cleaners would be much appreciated.


I have a heck of a time getting the fiberglass clean, the dirt seems to stick to it like glue and scrubbing is useless. It's very frustrating. Thanks so much for your help.

By AnnahFM from Toronto, Ontario, Canada


Cleaning a Fiberglass Tub

Try spraying with bleach. (04/14/2009)

By vguy

Cleaning a Fiberglass Tub

Bleach is good at killing mold. I would put a little bleach in some water and clean it with that. It still won't look clean, but it should kill the mold.

There is a product called Polyblend Grout Renew. It is a colorant, has mildew preventer in it and is also a sealer, and the bottle says it is stain resistant. I got it at Home Depot in the flooring department, it comes in different colors.

I wanted to do the grout in my bathroom, ceramic tile floor, wall and around the tub, but they didn't have the exact color to match any of the grout, so I just bought the nearest color to it. You apply it with an old toothbrush and while still wet, you wipe over it with a dry rag.

This stuff covered all of the grout which is now a uniform color and made it all look like new, and it actually is stain resistant. I did it about 6 mos. ago and it still looks like I just did it. It is made by Custom Building Products in Seal Beach, California. (04/14/2009)

By Anonymous

Cleaning a Fiberglass Tub

I bet it isn't Grout but is Caulking instead. Either way, you can use straight bleach to clean caulk or grout. Just pour or spray it on, shut the bathroom door, and leave the bleach to sit for about 20 minutes or so. If it's caulk and not grout, sometimes mold will get into caulking. If it is caulk, it's very easy to re-caulk. They sell a bathroom caulk that resists mold. All you have to do is scrape the rubbery caulk out then re-caulk. Ask at the hardware store, there is lots of cool tips & tools to help caulk a neat line. (04/14/2009)


By Cyinda

Cleaning a Fiberglass Tub

I use Tilex. If that doesn't work, it's under the caulk and should be removed and reapplied. As far as cleaning a fiberglass tub. I have two products that I use on mine. Bar Keeper's Friend. It's a cleanser like Comet or Ajax and melts away the crud like you wouldn't believe. The second is the Mr. Clean Eraser. Wonderful, wonderful, they will scrub out the remainder of the crud. Blessings! (04/16/2009)

By Sheryllynn44

Cleaning a Fiberglass Tub

Try using Scrubbing Bubbles. I clean houses and I swear by this product. (04/17/2009)

By busdrivr

Cleaning a Fiberglass Tub

I also would use a magic eraser on the grout and /or scrub with an old toothbrush dipped in spic n span with water. The fiberglass is frustrating. I once tried a magic eraser on my shower (out of desperation) and now rust stains are so embedded. I think that the eraser sort of micro-scratched the surface. So, try CLR or something like it. Use a scrubby with circular motions dipped in borax or softscrub. I feel your pain! (04/17/2009)

By captarlo

Cleaning a Fiberglass Tub

I will add a PS to my post below, Polyblend Grout Renew works with both grout and caulk. (04/18/2009)

By Anonymous

June 9, 20160 found this helpful

To clean the corner shelves in our son's shower, I line the wall rim and corners with paper towels and then pour clorox on. Let it set for several hours, remove, and wipe down. It really worked in his shower and I use it on the wall rim of our tub. Just be sure to have a lot of ventilation. Clorox does have a strong smell. Hope this works for you.

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June 20, 20160 found this helpful

Use either natural cotton (like for first aid) or twisted papertowel, place it where the mold is and spray with bleach and leave it until peeking under it shows the black is gone. Can do the same thing with white vinegar. After cleaning, spray the area with white vinegar and leave it to dry. It stops mold and fungus in porous materials (grout) and even painted drywall

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December 10, 20160 found this helpful

Bleach will not kill mold it will make it go away for a little while it is a proven fact that Lysol kills the mold the health department of tell you that please just makes it go away then it comes back Lysol kill it from being active and then you need to get you something to paint it or cure it to keep it from coming back

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