Symptoms
- Grout looks dingy yellow or brownish compared to when installed
- Discoloration spread across most grout lines evenly
- Grout feels slightly sticky or gritty
- No cracking, just color change
Likely causes
- CommonSoap scum and body oil buildupGrout is porous and absorbs residue from soap and skin over repeated showers.
- CommonHard water mineral stainingCalcium and other minerals can leave a yellowish film embedded in the grout surface.
- PossibleGrout sealer breaking down or discoloring with ageSome older sealers yellow themselves over time, especially with UV or heat exposure.
- Less commonLow-level mold or mildew not yet visibly blackEarly-stage mildew can tint grout yellow or off-white before turning darker.
What to do
- Mix a paste of baking soda and water, or use an oxygen-based grout cleaner.
- Apply the paste to the discolored grout lines and let it sit for 10–15 minutes.
- Scrub with a stiff nylon brush or old toothbrush, working along the grout lines.
- Rinse thoroughly with clean water and check the color; repeat if needed for stubborn stains.
- For deeper staining, use a dedicated grout whitening product or diluted oxygen bleach solution.
- Once clean and fully dry, apply a fresh coat of grout sealer to help resist future staining.
- Improve ventilation after showers going forward to slow the buildup that causes discoloration.
Tools and parts
- Stiff nylon brush
- Baking soda
- Grout sealer applicator
Grout sealerSearch: “penetrating grout sealer”
When to call a pro
Consider a tile professional if cleaning and resealing don't restore the color, since deep staining may require professional-grade treatment or regrouting.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.