Checked for accuracy and updated on September 21, 2026.
Grout trouble usually shows up one of two ways. Either the color has gone gray and blotchy while the joints themselves are still solid, or a piece of the grout has actually cracked, chipped, or fallen out. Those are two different problems, and reaching for the wrong product means either wasting money on a tool that can’t do the job, or doing more work than the repair actually needed.
Is your grout damaged, or just dirty?
Before buying anything, press a fingernail or a small screwdriver tip into the grout line. If it’s hard and doesn’t move, the grout is structurally fine and the problem is cosmetic: staining, soap scum buildup, or color that’s simply faded from years of cleaning. If material comes away, crumbles, or the joint has a visible gap down to the substrate, that’s an actual structural repair.
This distinction matters because the two fixes are not interchangeable. A grout colorant pen sits on top of existing grout and recolors it; it does not fill gaps or rebuild a joint. A premixed grout filler is an actual repair material that goes into a missing or cracked section; it is not designed as a whole-floor color treatment.
Cosmetic fix: recoloring grout that’s still sound
When the grout itself is intact but looks dingy, a grout pen is the simpler and cheaper option. It’s a marker-style applicator filled with a water-based acrylic colorant that both tints and lightly seals the grout line as you draw over it, which is why manufacturers also market these as “grout restorers” rather than paints.
Check price on Amazon: Grout Pen. This is an affiliate link (see our disclosure for details).
A few things worth knowing before using one. It only works on grout that hasn’t already been sealed, since a sealer blocks the colorant from bonding; the manufacturer’s own instructions suggest a quick water-drop test first (if water soaks in within a minute, the grout is unsealed and ready). The narrow-tip version is meant for standard grout lines around 2mm wide; wider or textured grout does better with the wide-tip version of the same product. And because it’s cosmetic, it needs to be redone periodically as the coating wears from foot traffic and cleaning, the same way any topical colorant would.
Structural fix: filling cracked or missing grout
When grout is actually chipped, cracked, or missing in small sections, a premixed grout filler is the right tool. Unlike bagged grout that has to be mixed with water to the right consistency, these come ready to apply straight from a squeeze tube, which matters for small touch-up jobs where mixing a batch for a few inches of joint isn’t worth the effort or the leftover waste.
Check price on Amazon: Red Devil Pre-Mixed Tile Grout. This is an affiliate link (see our disclosure for details).
The application itself is straightforward: cut the tube nozzle at an angle to roughly match the joint width, apply directly into the damaged section, and smooth it with a damp float or cloth before it skins over. Most premixed grouts of this type are a siliconized-acrylic formula rather than traditional cement-based grout, which is part of why they cure by drying rather than by a chemical set. Expect a full cure window of one to two days before the area sees regular water exposure, even though it may feel dry to the touch much sooner.
What neither product fixes
Both of these are surface-level repairs, and it’s worth being honest about where that stops working. If grout keeps cracking in the same spot repeatedly, or if a section is loose because the tile itself has shifted, the underlying cause is usually movement in the substrate or a failed original installation, not a grout problem you can patch your way out of. Filling the same crack twice in one year is the signal to stop patching and get the tile assessed, since a repeat crack is telling you something about what’s happening underneath it, not about which product you used.
Similarly, if water has been getting behind the tile (evidenced by soft drywall nearby, a persistent musty smell, or grout that stays damp long after the room has dried), that’s a moisture problem that needs solving before any grout repair, cosmetic or structural, is worth doing at all.
Keeping grout from needing this fix again
Once grout is repaired and cured, a separate penetrating sealer applied every 12 to 18 months is what actually slows down future staining and cracking from moisture cycling. That’s a different product from both of the ones above; a grout colorant pen includes a light sealing property as a side effect of the coating, but it’s not a substitute for a dedicated penetrating sealer on unglazed or textured grout that sees regular water exposure, like a shower floor.
Etienne Basson maintains and repairs his own home, and writes practical guides on choosing the right materials and products for repair and finishing jobs: fillers, sealants, adhesives, and similar. He focuses on what actually works for a specific job, not just a spec sheet.