Yes, bleach can clean grout — but only used alone, in a ventilated room, and never combined with any other cleaner already on the surface.
Grout is porous, which is exactly why it stains and grows mildew so easily, and why bleach became the go-to fix for dingy white grout lines.
It works well on plain white grout, but it's strong enough to cause real damage if used on the wrong surface or without basic precautions.
Dilute bleach with water — a common ratio is about 1 part bleach to 10 parts water — or use a bleach-based grout cleaner as directed on the label. Apply it to the grout lines only, let it sit for 5 to 10 minutes, then scrub with a stiff brush or old toothbrush and rinse thoroughly with plain water.
Open a window or run the bathroom fan, and never use bleach in a small closed room without airflow. Wear gloves, and never apply it on top of vinegar, ammonia, or any other cleaner still on the surface — rinse and dry the area first if you used something else recently.
Skip bleach on colored or dyed grout, since it can lighten or blotch the color permanently. It's also too harsh for natural stone tile like marble, travertine, or limestone, which bleach can etch and dull over time.
For colored grout or stone, use a stone-safe grout cleaner, or scrub with a baking soda and water paste and a stiff brush, then rinse well.
Save bleach for occasional deep stains rather than a weekly routine — frequent use can wear grout down faster. For regular maintenance, a mild grout cleaner or diluted dish soap is usually enough.
Bleach can restore stained white grout, but it's a job for occasional deep cleaning, not a weekly habit. Ventilate the room, use it alone, and reach for a gentler cleaner on colored grout or stone.
About 5 to 10 minutes is usually enough for diluted bleach to loosen stains. Leaving it longer doesn't clean much better and increases the risk of surface damage.
It's best to avoid it — bleach can lighten or blotch colored grout permanently. Use a grout cleaner labeled safe for colored grout instead.
Only with the door open, a fan running, or a window cracked. Skip it entirely in a bathroom with no ventilation at all.
A baking soda and water paste scrubbed in with a stiff brush handles light to moderate stains well, and it's safe for colored grout and most stone surfaces.