Grout is porous, light-colored cement wedged into the lowest point of every tiled surface — which makes it a magnet for dirt, mildew, and stains. If your once-white grout lines have gone gray or brown, you are not looking at damage so much as decades of trapped grime. Knowing how to clean tile grout the right way can restore lines to nearly their original color without harsh scrubbing that wears the grout down. The trick is matching the method to the mess and sealing afterward so it stays clean.
Part of our Tile & Grout guide — explore the full guide →
- How to Clean Tile Grout: Why Grout Gets So Dirty
- Start With the Gentlest Method
- The Baking Soda and Vinegar Method
- Oxygen Bleach for Deep Stains
- Steam Cleaning: The Chemical-Free Option
- When to Call in a Professional
- Seal It So It Stays Clean
- Choosing the Right Brush and Tools
- Special Cases: Colored and Stone Grout
- Removing Mold and Mildew in Showers
- A Simple Maintenance Routine
How to Clean Tile Grout: Why Grout Gets So Dirty
Grout’s cement composition is full of microscopic pores that soak up spills, soap scum, and moisture like a sponge. On floors, foot traffic grinds dirt into those pores. In showers, constant humidity feeds mildew and mineral buildup from hard water. Because grout sits slightly recessed below the tile surface, everything that rolls across the floor eventually settles into the lines.
Colored and sealed grout resists this better, but even sealed grout loses its protection over time. Once the sealer wears off — usually within one to two years — the pores are exposed again and staining resumes. That is why cleaning and resealing go hand in hand.
Start With the Gentlest Method
Always begin with the least aggressive approach and escalate only if needed. Harsh acids and stiff wire brushes can erode grout permanently, so save them for last resorts. For routine dinginess, warm water and a stiff nylon brush remove a surprising amount of surface grime before any cleaner is involved.
Spray the grout with plain hot water, let it sit for a minute to loosen debris, then scrub along the lines with a grout brush or an old toothbrush. Wipe away the loosened dirt with a clean cloth. For light everyday buildup, this alone often does the job.
The Baking Soda and Vinegar Method
For moderate staining, a baking soda paste is the workhorse of grout cleaning. Here is the process:
- Mix baking soda with a little water into a thick paste and spread it directly over the grout lines.
- Spray white vinegar over the paste — it will fizz as the two react, lifting grime.
- Let it sit for five to ten minutes so the reaction and mild abrasion do the work.
- Scrub with a grout brush, then rinse thoroughly with clean water.
One important caution: never use vinegar on natural stone tile like marble, travertine, or slate. The acid etches and dulls stone permanently. Vinegar is only safe around ceramic and porcelain. For stone, skip the vinegar and use baking soda with hydrogen peroxide instead.
Oxygen Bleach for Deep Stains
When grout has gone gray from years of buildup, oxygen bleach is the safest heavy hitter. Products like OxiClean, mixed with warm water into a slurry, penetrate the pores and lift deep stains without the fumes or fabric damage of chlorine bleach. Spread the solution over the grout, let it dwell for 15 to 30 minutes, then scrub and rinse.
Oxygen bleach is far gentler on colored grout than chlorine, which can lighten or blotch dyed grout unevenly. It is also better for indoor air quality. For truly stubborn shower mildew, chlorine-based grout cleaners work faster, but ventilate well and never mix them with any other cleaner.
Steam Cleaning: The Chemical-Free Option
A handheld or floor steam cleaner blasts hot vapor into grout pores, loosening grime and killing mildew with zero chemicals. Run the steamer’s nozzle slowly along each line, then wipe with a microfiber cloth. Steam is especially effective in showers, where heat dissolves soap scum and sanitizes at the same time.
The trade-off is that steam alone may not remove years-old set-in stains that have discolored the cement itself. For those, pair a steam pass with an oxygen bleach treatment. But for regular maintenance and mildew control, steam is fast, safe around pets and kids, and requires nothing but water.
When to Call in a Professional
If your grout is cracked, crumbling, or stained so deeply that no method restores it, cleaning has reached its limit. At that point you have two options: professional grout cleaning with truck-mounted extraction equipment, which runs roughly $1 to $2 per square foot, or grout color sealing. A color seal applies a pigmented epoxy coating over the grout, giving old lines a uniform fresh color and a built-in stain barrier.
Regrouting — removing the top layer and applying fresh grout — is the fullest fix and costs more, but it is the answer when grout is physically deteriorating rather than just dirty.
Seal It So It Stays Clean
Cleaning is only half the battle. Once grout is clean and fully dry, apply a penetrating grout sealer with a small applicator bottle or brush, working it into the lines and wiping excess off the tile. A quality sealer fills the pores so future spills bead up instead of soaking in.
Reseal every one to two years in wet areas and high-traffic floors. Sealed grout is dramatically easier to keep clean — a quick wipe handles most messes before they can stain. This single step saves you from repeating the deep-cleaning process every few months.
Choosing the Right Brush and Tools
The tool you scrub with matters as much as the cleaner. A dedicated grout brush with stiff nylon bristles reaches into the recessed lines and applies pressure right where the grime sits. An old toothbrush works for small areas and tight corners, but it wears out fast on a large floor. For big jobs, an inexpensive rotary drill brush attachment saves your hands and shoulders — spin it slowly along the lines and let the bristles do the work.
What you should avoid is a metal wire brush. Steel bristles gouge and erode cement grout, thinning it and creating rough channels that trap even more dirt going forward. The same caution applies to abrasive scouring pads on the tile face, which can scratch glazed surfaces and dull polished stone. Match the aggressiveness of your tool to the delicacy of your surface, and always test in an inconspicuous corner first.
Special Cases: Colored and Stone Grout
Not every grout responds to the same treatment, and using the wrong cleaner can ruin the look. Colored grout — the dyed tans, grays, and charcoals popular in modern tile work — can fade or bleach unevenly if you hit it with chlorine bleach. Stick to oxygen bleach or a gentle baking soda paste on colored grout to preserve the pigment.
Natural stone tile brings its own rules. Marble, travertine, limestone, and slate are acid-sensitive, so vinegar, lemon juice, and many commercial bathroom cleaners will etch and dull them permanently. Around stone, use only pH-neutral cleaners or a baking soda and hydrogen peroxide paste, and rinse thoroughly. When in doubt about your grout or tile type, the safest starting point is always the gentlest method, escalating only if it fails to lift the stain.
Removing Mold and Mildew in Showers
Shower grout faces a tougher enemy than floor grout: constant moisture that breeds black mold and pink mildew in the lines. For surface mildew, a paste of baking soda and hydrogen peroxide spread on the lines, left for 15 minutes, then scrubbed, kills and lifts most growth without harsh fumes. For stubborn black staining that has penetrated deeper, a diluted chlorine bleach solution — one part bleach to three parts water — applied with a brush and rinsed well is more effective, but ventilate the bathroom and never mix it with any other product.
If mold keeps returning no matter how often you clean, the grout or the caulk may be harboring growth beneath the surface, or moisture may be getting behind the tile. In that case, removing and replacing the affected caulk and resealing the grout addresses the root cause rather than treating the symptom over and over.
A Simple Maintenance Routine
Prevent buildup rather than fighting it. In the shower, keep a squeegee handy and wipe down walls after each use to cut the moisture mildew needs. On tile floors, sweep or vacuum regularly so grit never gets ground into the lines, and damp-mop with a pH-neutral cleaner rather than harsh soaps that leave residue.
A monthly light scrub with baking soda paste keeps grout from ever reaching the deeply stained stage. Clean grout is mostly a matter of consistency: seal it, wipe up spills promptly, and give it a quick brush now and then. Do that and you will rarely need the aggressive treatments at all — which is exactly the point.
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