I have an acrylic bathtub that meets up against marble tile. I thought this was hard grout at first because it has a gritty finish, but poking at it with a knife reveals it to be somewhat flexible. What kind of grout would be like that?

Anyway, my understanding is the grout must be removed and caulk suitable for acrylic must be used. I have never done this sort of thing before and I have a couple questions

  1. Should I used a hand grout saw to remove the grout or an oscillating tool? I'm worried I'll damage the tub or the tile with the power tool, but also using a handsaw may take forever.

  2. How much of the grout do I need to remove? Just a groove over the crack or as much as possible?

  3. What would be the appropriate caulking product for this?

  4. is a hand-powered caulking gun sufficient?

Here is what the grout looks like enter image description here

  • 1
    If it's flexible, it's highly unlikely that it's actually grout, and is most likely caulk of some sort. Usually a "tile and tub" silicone caulk is what's used around a tub.
    – FreeMan
    Commented Apr 17, 2022 at 14:24

1 Answer 1


Yes, you need to use whatever tool you are comfortable with to remove the grout.

Clean it with a vacuum and a wipe of Acetone or Denatured Alcohol before caulking. Denatured Alcohol would be best in case you are calling fiberglass, acrylic. Denatured Alcohol won't hurt either.

Try and find a Urethane Acrylic caulk, this will last the longest. Don't skimp on price.

  • 3
    And fill the bath, so the gap is biggest...
    – Solar Mike
    Commented Apr 16, 2022 at 20:57
  • Thanks. Won't acetone damage the acrylic tub?
    – marathon
    Commented Apr 16, 2022 at 23:16
  • If it's fiberglass yes, acrylic, no. Use Denatured Alcohol, it won't damage either.
    – Rob West
    Commented Apr 17, 2022 at 23:34

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