Quick answer
Ventilate, put on gloves and a mask, and apply 3% hydrogen peroxide or bleach diluted 1 to 10 to the mould for 15-30 minutes, scrub with a brush and rinse. If the mould stays in the sealant, it is inside and the sealant needs renewing with anti-mould sanitary sealant. Never mix bleach with vinegar or ammonia. To prevent it, ventilate for 15 minutes after every shower.
What you need
- Nitrile or rubber gloves
- FFP2 mask and glasses
- Old toothbrush
- Spray bottle
- Microfibre cloth
- Shower squeegee with a rubber blade
- Plastic spatula
- 3% hydrogen peroxide (10 volume), from a pharmacy or Mercadona
- Cleaning bleach (only if you are not using any acid that day)
- Kitchen paper
- White vinegar, only for a separate treatment
- Anti-mould sanitary sealant: Sika, Pattex Baño Sano or Ceys
- Isopropyl alcohol to degrease before resealing
- Masking tape
Step by step
- 1
Ventilate and protect yourself
Open the window and switch on the extractor fan. Put on gloves, glasses and an FFP2 mask: mould releases spores when you scrub. If there is asthma or allergy in the household, do not do it yourself without protection.
- 2
Remove soap and dust
Run a sponge with warm water and neutral soap over the grout and sealant. Soap grease protects the mould and makes the product work less well. Rinse.
- 3
Decide on the product
Choose only one: 3% hydrogen peroxide, which is mild and does not smell, or bleach diluted one part to ten of water, which is faster and more effective. If you have already used vinegar or descaler today, wait until the next day before using bleach.
- 4
Apply the product to the mould
Spray the grout and sealant. For vertical stains, soak kitchen paper and stick it over the mould so it does not run. On thick sealant, leave it half an hour.
- 5
Leave it to work
With hydrogen peroxide, 20 to 30 minutes. With diluted bleach, 10-15 minutes, never longer. Do not let it dry out completely. Keep the bathroom ventilated.
- 6
Scrub with a brush
Brush the tile grout and go over the sealant with a soft brush. Do not scrub the sealant hard: if it cracks, water gets in. If the mould comes off well, you have finished the hard part.
- 7
Rinse and dry
Rinse with plenty of water, several times. Run the squeegee over and dry with microfibre. Look at the lines in good light: if they are still black or grey after two applications, the mould has penetrated the sealant.
- 8
Renew the sealant if it will not come out
Remove the old sealant with a blade and a sealant remover, clean with isopropyl alcohol and apply new anti-mould sealant. The full process is in how to remove old silicone from tiles and bath. Wait 24 hours before it gets wet.
- 9
Tackle the cause: ventilation
Fit or clean the extractor fan, leave the window open for 15 minutes after the shower and dry the walls and screen with a squeegee. With a small dehumidifier in windowless bathrooms, humidity drops below 60%.
- 10
Check there is no leak
If mould appears every few weeks in one particular spot, look for a leak at the tray, the screen or the wall. Damp rising from inside is not fixed by cleaning. There are pointers in how to remove mould from a wall.
Why mould grows in the shower and what you need to tackle
Mould needs three things: damp, lack of ventilation and food. The shower has all three: steam, a closed bathroom and soap residue and body grease in the sealant and grout. Cheap or old sanitary sealant is porous and holds moisture, which is why mould settles there first.
If you only clean the stain, the mould comes back within weeks. To stop it coming back you have to bring the bathroom humidity below 60% and renew the sealant when it is no longer waterproof. That is the difference between cleaning and removing mould for good.
| Where it appears | Why | What to do |
|---|---|---|
| Grout between tiles | Porous cement and damp | Clean with hydrogen peroxide or diluted bleach; regrout if it is old |
| Sealant on the tray or screen | Old sealant or one without anti-mould | Clean; if it does not come out, replace the sealant |
| Corners and ceiling of the bathroom | Condensation and poor ventilation | Extractor fan and dehumidifier |
| Behind the screen | Water standing in the profiles | Dry with a squeegee and clean the tracks |
| Grating and waste | Soap residue and hair | Clean weekly |
| Shower curtain | Constant damp | Wash at 60 °C or replace |
How to remove mould from shower grout and sealant, by product
3% hydrogen peroxide is the mildest option: it has no smell, does not damage most finishes and whitens. It works very well on tile grout and sealant with surface mould. It is slower than bleach, but safer in small bathrooms and in homes with children or pets.
Diluted bleach (one part to ten of water) works in ten minutes and is the most effective on badly blackened cement grout. You must ventilate, wear gloves and rinse thoroughly. And it must never be brought together with vinegar, descaler, drain cleaners or ammonia: chlorine gas is released.
White vinegar reduces light mould, but does not eliminate it completely from porous grout. It is useful for limescale, less so for deep mould. Use it in a separate treatment, on another day, with the bathroom already rinsed. For tile grout, there are more options in how to clean tile grout.
Common mistakes when removing mould
- Mixing bleach with vinegar, descaler or ammonia. It is the most dangerous mistake. One product at a time, rinsing in between.
- Applying bleach and shutting the bathroom again. Without ventilation, you breathe in fumes and the mould returns.
- Sealing over mouldy sealant. New sealant does not stick to a dirty base. The old one has to be removed.
- Using kitchen or building sealant. It has no anti-mould. In the shower use anti-mould sanitary sealant.
- Scraping the sealant with a scouring pad. It cracks it and water gets in through the crack.
- Painting over a mouldy wall. It reappears within weeks. First clean it and find out where the damp is coming from.
When to call a professional
If the mould returns in less than a month, there are marks on the wall or ceiling outside the shower, or the whole bathroom smells damp, there may be a leak, seepage from the tray or structural condensation. In that case, cleaning is not enough: the source has to be found.
At Manitas Costa, resealing with anti-mould sealant costs €40-70, removing an old shower screen to reach the joint €50-65 and fitting a new one €90-170. If the tile grout has crumbled, regrouting a whole bathroom costs €150-300 with a builder and replacing 1-5 tiles €60-120. Always at a fixed price before we start.
Details in shower screens and sealing and shower screen prices. For regrouting and damp, builder by the hour. If the sealant is what needs changing, see how to seal a shower screen. In Alicante: shower screens in Alicante.
Damp on the coast: how to stop the mould coming back
In Benidorm, Torrevieja, Villajoyosa or Valencia, the ambient humidity hovers around 65-75% for much of the year. A bathroom with no window or with a small extractor fan does not dry out. Three habits change the result: ventilate for 15 minutes after every shower, run the squeegee over the tray and screen, and use a dehumidifier if the bathroom has no window.
In holiday lets, mould appears after weeks of being shut. Leave the bathroom door open, the extractor on a timer and, if possible, a small dehumidifier. On the seafront, salt air speeds up the deterioration of sealant: renew it every four years. And after cleaning, keep the tiles and the screen in good condition with how to clean limescale off a shower screen.
Frequently asked questions
What kills shower mould permanently?
No product does it for ever. 3% hydrogen peroxide or diluted bleach will remove it, but it returns if the bathroom stays damp and badly ventilated. The lasting fix combines cleaning, new anti-mould sealant if the old one is porous and ventilation: 15 minutes after every shower and a squeegee on the tray and screen.
Can I use vinegar and bleach together for mould?
No. The mixture releases chlorine gas, which irritates the eyes and airways. If you want to use both, do it on different days, rinsing thoroughly and ventilating. In practice, hydrogen peroxide or diluted bleach is enough, and vinegar is kept for limescale.
How do I know if the sealant needs replacing?
If after cleaning with hydrogen peroxide or bleach the black marks remain, the mould is inside. Also if the sealant is yellow, peeling or cracked. Replacing it costs €40-70 with us and stops water getting behind the tray or screen and damaging the wall.
Is shower mould dangerous to health?
It can irritate the nose, eyes and throat, and worsen asthma or allergies, especially in children and older people. A small mark on the sealant can be cleaned at home with gloves and a mask. If mould has spread over walls and ceiling, it is worth finding the cause of the damp.
How often should shower sealant be replaced?
Every four to five years, or sooner if it blackens and will not come clean. In seafront homes or those with poor ventilation, every three or four. Choose anti-mould sanitary sealant from makes such as Sika, Pattex or Ceys, and leave it to cure for 24 hours before using the shower.