Bathroom

Clean dirty grout without harsh chemicals

The grout lines in your shower used to be white, and now they're a patchy shade of gray. Grout is porous, so it soaks up grime. Clean dirty grout with the right paste and brush, seal it, and it'll look close to new.

Written and reviewed by Grab the Hammer Team · Updated Sep 2026
Scrubbing dirty tile grout with baking soda paste and a stiff brush, before and after
How to clean grout: spread baking soda paste on the dirty lines (1), scrub along them with a stiff grout brush (3), wipe clean (2), then seal once dry.

What's actually going on

Grout is basically sand and cement, full of tiny pores. Everyday grime settles into those pores, which is why wiping the surface never quite gets it clean. You need something mildly abrasive and a brush narrow enough to work into the line, plus a little patience.

Why it happens

Soap scum and body oils

They settle into the grout's pores in showers.

Mildew

Dark spots in damp corners are usually mildew.

Mopping with dirty water

On floors, dirty mop water gets pulled into grout lines.

No sealer

Unsealed grout absorbs everything.

Before you startSkip vinegar and bleach on natural stone like marble or travertine. Both can etch the surface.

Let's fix it

0 of 5 done
  1. Mix a pasteStir baking soda with a little water until it's like toothpaste.
    Baking soda stirred with a little water in a bowl until it's as thick as toothpaste
  2. Spread it on the groutWork in a small area at a time, about 2 by 2 feet. Spread the paste along the lines and mist it lightly.
    Baking soda paste spread along the grout lines of a small section of tile
  3. Scrub along the lineScrub back and forth along the grout, not across it. Let the brush do the work.
    Stiff grout brush scrubbing back and forth along the grout line, not across it
  4. Rinse and wipeWipe away the paste with a damp cloth, rinsing often, then dry the area.
    Damp microfiber cloth wiping away baking soda paste and revealing clean grout
  5. Seal once it's fully dryWait 24 hours, then brush on a penetrating grout sealer. It keeps stains from soaking back in.
    Small brush applying penetrating grout sealer along a clean grout line after 24 hours

Still not fixed?

If stains won't budge, try 3% hydrogen peroxide mixed with baking soda. For really dark grout, a grout colorant can make it look even again.

Crumbling, cracked or missing grout needs regrouting, not cleaning, or water will get behind the tile.

Tip from experienceFor stubborn stains, swap the water in your paste for 3% hydrogen peroxide. It lifts mildew stains without the fumes of bleach.
Time to call a pro if you seeCracked or crumbling grout, loose tiles, or grout that turns dark again within days. That usually means water is getting behind the tile.

What a pro charges: Professional grout cleaning often runs $150–$400 per room. Regrouting a shower typically costs $300–$800.

Common questions

What's the best homemade grout cleaner?

A paste of baking soda and water, or baking soda and 3% hydrogen peroxide for stains, scrubbed with a stiff grout brush.

How often should grout be sealed?

About once a year in showers, every few years on floors.

When should grout be replaced instead of cleaned?

If it's cracked, crumbling, or stains come back right away, cleaning won't fix it. Regrouting or a grout colorant is the next step.

About the authors

Grab the Hammer Team

We're a small team of home repair writers and editors who test our advice against manufacturer instructions and common code requirements. Our goal is simple: help you fix what you safely can, and know when to call in a pro.

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