Maintenance and repairs
Cleaning grout: how to clean and restore white grout in the bathroom
White grout in the bathroom turns grey from dirt and soap and black in the shower from mould. Regular dirt can be cleaned with a grout cleaner and a stiffer brush, not a wire brush – then rinse the grout with clean water and let it dry. Acidic cleaners damage cement grout, so according to the manufacturer Mapei, do not leave them on for long and always rinse them off. Sealing (impregnation) protects cleaned cement grout, for example, Ceresit CT 10. If the grout still doesn't look good, grout colourant or new grouting can help.
Illustrative image: white clean grout between light wall tiles in the shower, next to a grout brush
A new bathroom with snow-white grout looks great. However, after a year, the grout on the floor turns grey and black spots appear in the corners of the shower. Most of the time, this is not damage, but dirt, soap, and mould that can be removed. We will explain what to clean the grout with, what harms it, how to protect it with sealing (impregnation), and what to do when cleaning no longer helps.
Why does grout darken
| What do you see | Cause | What helps |
|---|---|---|
| grey grout on the floor | dirt from shoes, grease | grout cleaner, brush |
| grey film in the shower | soap, shampoo, skin oils | grout cleaner, squeegee after showering |
| black spots in the corners and by the shower tray | mould from dampness | mould remover, ventilation |
| white hard residue | limescale | briefly acidic cleaner, then rinse |
| the grout is crumbling, has holes | worn or poorly grouted grout | scrape out and regrout |
Cement grout is porous – it absorbs water and dirt. Epoxy grout is smooth and does not absorb dirt, which is why it is used in showers and areas that require frequent cleaning. The difference between them is described in the chapter Grout and silicone.
What harms the grout
Cement grout is alkaline and acids damage it. The manufacturer Mapei warns with its acidic cleaner: do not leave it on the grout for long, always rinse thoroughly with clean water – residues can change the colour of the grout over time – and moisten the surface with water before cleaning. With another acidic product, Mapei states that it can damage, lighten, or change the colour of cement grout.
- Acidic cleaners and limescale removers – only for limescale, briefly and on a damp surface, never on polished marble, limestone or cement terrazzo.
- Wire brushes and sharp tools – can scratch the grout and glaze of the wall tiles.
- Mixing products – never mix chlorine-based products with acidic cleaners, as toxic gas is released.
- Fresh grout – Ceresit recommends washing CE 40 grout only with clean water for the first 5 days, without cleaning agents. Acidic cleaners should be used according to Mapei only on fully cured grout, which is typically after 1 to 10 days depending on the type of grout.
How to clean white grouts step by step
- Ventilate and put on gloves.
- Dampen the grouts with clean water.
- Apply cleaner to the grouts – a product designed for grouts and wall tiles, diluted and left to act according to the instructions. Mapei, for example, produces a cleaner suitable for both epoxy and cement grouts.
- Scrub with a brush with stiffer bristles or an old toothbrush, along the grout joint. Not with a wire brush.
- Rinse with clean water and wipe to ensure no cleaner or dissolved dirt remains on the grouts.
- Let it dry – a wet grout appears darker; you will see the true colour only after it dries.
- Seal dry cement grouts if you want them to stay clean longer.
A steam cleaner or a mop with microfibre will help on the floor – but check the instructions for the wall tiles and grout to see if the manufacturer allows it. Do not use a steam cleaner on taps and shower glass. How to remove limescale from taps without damage is described in the article Limescale on taps.
Mould in grouts and silicone
Black spots in the corners of the shower, by the shower tray and bathtub are mould. Use a mould remover according to the instructions on the grouts and rinse it off after the recommended time. Chlorine-based products may lighten some coloured grouts, so test them first in a hidden area. Mould in silicone cannot be cleaned permanently – the silicone needs to be cut out and replaced with new, the procedure can be found in the article Replacing silicone in the bathroom.
If mould returns, the issue is with ventilation. After showering, steam needs to be vented out through a window or fan with a timer – more in the article Mould in the bathroom.
Sealing: to keep grouts clean
Sealing closes the pores of the cement grout – water and dirt will not easily penetrate. Ceresit, for example, recommends silicone sealing CT 10 as suitable for additional sealing of grouts, wall tiles and floor tiles in bathrooms and showers.
| Step | Ceresit CT 10 according to the technical data sheet |
|---|---|
| substrate | clean and dry, mechanically remove efflorescence |
| application on grouts | with a brush, usually one coat is sufficient |
| excess | after about 5 minutes, wipe off and clean the surface with a damp cloth |
| water resistance | after 2 to 6 hours |
| full effect | after about 14 days |
Epoxy grouts do not require sealing. For natural stone and tiles with absorbent surfaces, choose sealing according to the material of the tile – in some cases, it may change colour. Always test it first on a small area.
Restoring the colour of grouts
When the grouts are clean but the colour is uneven or greyed, grout colourant can help. Mapei UltraCare Fuga Fresca is a ready-to-use colourant for restoring or changing the colour of cement grouts indoors, available in 40 shades according to Mapei grout colours. It is applied in a thin layer to cleaned and dry grouts, and any colour that gets on the wall tiles should be wiped off according to the instructions. Always follow the procedure and drying time according to the manufacturer's technical data sheet.
When cleaning doesn't help: re-grouting
If the grout is crumbling, has holes or is stained even after cleaning, it needs to be restored. Scrape out the old grout with a grout scraper or oscillating tool with a grout attachment, being careful not to damage the edge of the wall tile. Do not use a grinder – Bosch warns that diamond cutting discs for cutting grouts are not intended for this and will damage the tiles. Mapei states for Ultracolor Plus grout that the grouts should be clean, dust-free, and empty at least two-thirds of the thickness of the wall tile before grouting.
- for bathrooms, choose a CG2WA class grout according to EN 13888 or an epoxy grout,
- in the shower, pay attention to waterproofing – under the grout is adhesive and beneath it is a liquid waterproofing membrane, which must not be cut through,
- corner grouts and transitions between the wall and floor should not be filled with grout, but with sanitary silicone – this is also stated by Ceresit,
- for large areas or damaged waterproofing in the shower, call a tiler.
How to grout and which grout to choose is described in the chapter Grouts and silicone and in the article Adhesive, grout and trims. If there is a cracked tile under the grout, see the article Cracked tile.
How to keep grouts clean
- after showering, squeegee the water off the glass and wall tiles,
- ventilate the bathroom after showering,
- clean grouts regularly with a neutral cleaner – dirt won't settle in,
- occasionally seal cement grouts,
- when renovating, choose epoxy grout or large format tiles with fewer grouts in the shower – see Bathroom without grouts.
Common mistakes
- acidic cleaner left on grouts for too long and not rinsed off,
- wire brush, knife or grinder on grouts,
- mixing chlorine and acidic products,
- sealing on a wet or unclean grout,
- spraying mould in silicone instead of replacing the silicone,
- cut waterproofing in the shower during grouting.
Grouts in various colours, epoxy grouts, and wall tile samples are available at our store in Senec. Schedule a visit. You can also find sanitary silicone and cleaning products in the category Sealants, adhesives and cleaning products at vkupelni.sk – for example, transparent sanitary silicone SAPHO 310 ml for €7.70 (November 2026).
Related: Grouts and silicone · Silicone replacement · Mould in the bathroom · Cracked tile · Bathroom maintenance and repairs
Sources: technical data sheets for Mapei UltraCare Acid Cleaner, UltraCare Sulfamic Acid Crystals, UltraCare Grout Cleaner, UltraCare Fuga Fresca, and Ultracolor Plus (CG2WA according to EN 13888), technical data sheets for Ceresit CT 10 (silicone sealing) and CE 40 (first 5 days without cleaning products, expansion and corner joints with silicone), Bosch – diamond blades for tiles (not for cutting joints), e-shop vkupelni.sk (sanitary silicone, price, November 2026).
Terms in the dictionary: Sealing (impregnation) · Shower tray · Grout · Epoxy grout (RG) · Sanitary silicone · Terrazzo
Frequently Asked Questions
How to clean white grout in the bathroom?
Moisten the grout, apply a cleaner designed for grout, scrub with a stiff-bristled brush and rinse with clean water. After drying, seal the cement grout to keep it clean for longer.
Can I clean the grout with acid or vinegar?
Only occasionally and briefly, for example on limescale. Cement grout is alkaline and acids damage it – Mapei warns that acidic cleaners should not be left on the grout for long and should always be rinsed off, otherwise they can change the colour of the grout.
How to remove mould from grout?
Use a mould remover according to the instructions and then rinse. Test chlorine-based products in a hidden spot first and never mix them with acidic cleaners. Replace mouldy silicone and ventilate the bathroom after showering.
How to seal the grout?
Apply sealing (impregnation) to clean, dry cement grout with a brush – for example, Ceresit CT 10 according to the technical data sheet in one coat. After about 5 minutes, remove the excess, it is water-resistant after 2 to 6 hours and has full effect after 14 days.
Can the grout be recoloured?
Yes, with grout colourant. Mapei UltraCare Fuga Fresca restores or changes the colour of cement grout indoors, applied in a thin layer to the cleaned dry grout. If the grout is crumbling, it needs to be scraped out and regrouted.
When should grout be regrouted?
When it is crumbling, has holes or is stained even after cleaning. Scrape out the old grout at least two-thirds of the thickness of the wall tiles and regrout with CG2WA grout or epoxy. In the shower, you must not cut through the waterproofing.
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