Symptoms
- Grout lines look darker, yellowed, or blotchy compared to when installed
- Stains concentrated in high-traffic or wet areas
- Grout looks dirty even right after mopping
- Mold or mildew tint in bathroom grout
Likely causes
- CommonEveryday dirt and grime absorbed into porous groutUnsealed or worn sealant lets grout soak up dirt like a sponge.
- CommonMold or mildew growth in damp areasBathrooms and other wet areas are prone to mildew staining in grout lines.
- PossibleGrout sealer worn off or never appliedWithout a sealer, grout stains much more easily and repeatedly.
- PossibleSpilled colored liquids (wine, coffee, colored cleaning products)Some stains penetrate deeply and resist basic cleaning.
What to do
- Sweep or vacuum the floor first to remove loose dirt before wet cleaning.
- Scrub the grout lines with a stiff nylon brush and a baking soda and water paste for general dirt and light stains.
- For mold or mildew stains, use a mixture of water and a small amount of oxygen bleach or a bathroom-safe mold cleaner, following product safety instructions and ventilating the room.
- Avoid chlorine bleach on colored grout, since it can lighten or discolor the grout itself.
- Rinse thoroughly with clean water and let the grout dry completely.
- For grout that's clean but was never sealed, apply a penetrating grout sealer to help resist future staining.
- For grout that's permanently discolored despite cleaning, a grout colorant/stain product can restore a uniform look without regrouting.
Tools and parts
- Stiff nylon brush
- Bucket
- Grout sealer applicator
Grout cleanerSearch: “grout cleaner stain remover”
Grout sealerSearch: “penetrating grout sealer”
When to call a pro
Call a tile cleaning service or professional for a whole-floor deep clean, or a tile installer if you'd rather regrout than clean.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.