In short: scrub grout with warm water and a mild detergent or a pH neutral tile cleaner, using a stiff nylon brush, then rinse and dry it. For stubborn mildew, use a product made for grout and follow its label. Never mix bleach with ammonia, vinegar or any other cleaner. Once the grout is clean and dry, a penetrating sealer helps keep it that way.
Why grout darkens in Florida
Most bathroom grout is cement based and porous. It soaks up water, soap and skin oils, and in a warm, humid bathroom it stays damp long enough for mildew to grow. Dark lines along the bottom rows and corners of a shower are usually a mix of dirt, soap scum and mildew, and hard water adds a white or gray film. For keeping humidity down, see our guide to mildew in a Florida apartment.
What to clean it with
| Cleaner | Good for | Cautions |
|---|---|---|
| Warm water and mild detergent | Everyday dirt and soap | Safe on most tile and grout |
| pH neutral tile and grout cleaner | Regular cleaning, and natural stone tile | Follow the label |
| Baking soda and water paste | Light stains, scrubbed in with a brush | Rinse well so no residue is left |
| Oxygen bleach cleaner | Darkened grout and mildew stains | Follow the label and test a hidden spot first |
| Chlorine bleach products | Mildew stains on white grout | Can lighten colored grout. Ventilate and never mix with another cleaner |
| Vinegar and acidic cleaners | Hard water film on glazed ceramic tile | Never on marble, travertine or limestone, which acids etch. Never with bleach |
How to clean it
- Open a window or run the exhaust fan, and wear gloves
- Rinse the tile with warm water to loosen soap and dirt
- Apply your cleaner to a small section and leave it for the time the label gives
- Scrub along the grout lines with a stiff nylon grout brush or an old toothbrush. Avoid wire brushes, which scratch tile and gouge grout
- Rinse with clean water and wipe the tile dry
- Leave the fan running until the grout is completely dry
What never to mix
Never mix bleach with ammonia or any other cleaner. That is the CDC's advice, and the EPA gives the same warning about ammonia. Mixing bleach with ammonia, or with acids such as vinegar and some toilet and lime scale cleaners, can release toxic gas. Use one product, rinse it off completely and let the room air out before you use another. Read the safety instructions on every product, and never use bleach in a closed room.
Sealing grout
- Seal only clean grout that has dried completely, as the sealer label directs
- A penetrating sealer soaks into the grout and slows how fast water and stains get in
- To check whether grout needs sealing, drip a little water on it. If it darkens quickly, the water is soaking in
- How often to reseal depends on the product and how much the shower is used. The label says
- If you rent, ask your landlord before sealing or using a new product on the tile
Keep it clean
- Squeegee or wipe the shower walls after each use
- Run the fan during and after showers
- Scrub the grout lines lightly every week or 2, before stains set
- Replace caulk that mildew has grown into, rather than scrubbing it again and again
When it is more than cleaning
Cracked or missing grout, loose tiles or grout that never dries lets water behind the tile. That is a repair, not a cleaning job. If you rent, report it to your landlord in writing. Grout that stays dark after a proper clean may need a professional clean or regrouting. Hard water film is covered in our guide to hard water marks in Palm Beach County.
A deep clean includes scrubbing grout and treating mildew. Send a request and a local cleaner will call you to quote.