I have a tile shower that is functional, but has some undesirable things about it:

  • The tile is white but much of the grout has become stained dark
  • There are areas where the grout has started eroding

The shower could use a remodel but it might be 5 years before I can make that happen. My question is this: If I go over all the grout with a grout pen, how long can I expect it to last? Will it prevent eroding grout from eroding further (at least for a year or two)? What are the downsides to using grout pen?

Thanks for any advice!


Use a grout saw (manual) to remove all the loose/failing grout and re-grout with black (or dark-colored - blue perhaps) grout.

Grout saw

White tile with white grout is dull even when it doesn't have issues. Dark grout also does not require the cleaning effort that white grout does. Tile is easy to clean, grout less-so. Here's a handy image of white tile with different grout colors.

white tile with different grout colors

I don't believe the "miracle" product will do anything useful for grout that is eroding. This should be a "one day out of the weekend" project, it's not a remodel. If you have an alternate shower/tub to use it could also be an "hour or two a day" project for a week, unless it's a gigantic shower with tiny tiles.

Looking into this a bit more I found several mentions of having no effect on mould, other than when you next scrub the mould, you have flakes of white paint coming off (since that's all it is.) Indeed, anti-mould spray was recommended for cleaning the grout. But given that you already have the grout failing I stand by the advice to replace it.

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A grout pen is just paint. Sure, it comes in a little handy applicator that's about the right size for painting grout lines, but it's still just paint.

So it makes sense to use only in situations where the grout is discoloured but otherwise fine. It won't help where there's mould, or in your case where the grout is falling apart.

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Bleach and scrub. Bleach and scrub. Repack cracks/low grout areas. Seal with grout sealer.
Do it again once a year.

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