Short answer
Sweep or vacuum first. Spread a paste of baking soda and water along the grout lines, wait 10 minutes and scrub with a stiff nylon brush or an old toothbrush. Rinse with clean water and wipe the tile dry. For grout that stays dark, use an oxygen bleach powder mixed with water, on its own. Once the grout is dry, a grout sealer keeps it clean longer.
Safety first
Use one cleaner at a time and rinse with water before you switch. Never mix bleach with vinegar, ammonia or other grout cleaners. Wear gloves and keep a window open or the fan on.
How to clean dirty grout
1Grout turns dark over time
Grout is porous. Soap scum, dirt and water soak in, and the lines go from white to gray to dark.
Read all the steps
- Grout turns dark over time. Grout is porous. Soap scum, dirt and water soak in, and the lines go from white to gray to dark.
- Spread a baking soda paste. Baking soda with a little water, thick like toothpaste. Spread it along the lines with a gloved finger or an old toothbrush.
- Wait 10 minutes, then scrub. A stiff nylon brush or an old toothbrush, in short strokes along each line. Never a wire brush: it eats the grout.
- Rinse and wipe dry. Rinse the paste off with clean water and a sponge, and wipe the tile dry so dirty water does not settle back in.
- Seal it once it is dry. Wait a day or two, then brush on a grout sealer. It keeps water and dirt out, so the next cleaning is easy.
- Still not fixed? Call a house cleaner Especially if: the grout stays dark after two deep cleanings, or there is mold in it over a large area.
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What not to do
- Do not mix bleach with vinegar, ammonia or other grout cleaners. Rinse well between products.
- Do not use vinegar or other acids on natural stone, and not often on grout: acid etches stone and wears grout down.
- Do not use a wire brush or a sharp tool: it scratches the tile and digs out the grout.
If it is still dark
Mix oxygen bleach powder with warm water as the label says, spread it on the grout, wait 10 to 15 minutes, scrub and rinse. Use it on its own, never with other cleaners. If the grout stays stained, cracks or crumbles, it may need a grout colorant or new grout.
Keep it clean longer
- Squeegee or wipe the shower walls after each shower.
- Mop floors with a mild, pH-neutral cleaner and clean water.
- Reseal the grout about once a year, or as the sealer label says.
When to call a house cleaner
- The grout stays dark after two deep cleanings, or there is mold in it over a large area.
- The grout is cracked, crumbling or missing (water can get behind the tile).
- The tile is natural stone, like marble or travertine, which needs stone-safe products.
- You want a whole bathroom or kitchen floor deep cleaned and sealed.
Frequently asked questions
What is the best way to clean grout?
A paste of baking soda and water and a stiff nylon brush handle most grout. For stains that stay, an oxygen bleach powder mixed with water, used on its own.
Can I use vinegar on grout?
Once in a while, diluted, on sealed grout next to ceramic tile. Acid wears grout down over time and etches natural stone, and it must never be used with bleach.
Does bleach clean grout?
It can lighten mold stains but does little for dirt, and it can fade colored grout. If you use it, ventilate, follow the label and never mix it with vinegar, ammonia or other cleaners.
How often should grout be sealed?
About once a year in showers and busy floors, or as the sealer label says. Drip some water on it: if it soaks in and darkens, it is time.
Why is my grout turning black?
Usually dirt and soap scum soaked into unsealed grout, or mold in wet spots like the shower. Clean it, keep it dry and seal it.