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How To Clean Black Mouldy Shower Grout Lines

Are the formerly sparkling white grout lines in your Adelaide shower or along the edge of your bathtub now black? You may have tried all sorts of professional-grade products, over-the-counter shower cleaners and natural recipes on the internet including vinegar, hydrogen peroxide and nothing has worked. You scrubbed as hard as you could using a stiff brush or a grout brush and it still won't budge. Maybe you even tried to steam clean your grout lines and even the steamer couldn't improve those heavy black mouldy lines? Your shower grout is likely looking something like this:

What You'll Need

When all else has failed there is one last resort that will work 99% of the time in Adelaide - the only time this won't work is when the mould has been absorbed into the grout itself, but even then it will improve the look by cleaning what is on the grount lines. Note that this method is not suitable for regular maintenance cleaning nor for all types of tiles including not for natural stone tiles such as limestone, marble and travertine; it's only for when all else has failed on standard white shower tiles, to save you the cost of a bathroom renovation or ensure you get your bond back for an Adelaide exit cleaning service. Always test on an inconspicuous area first and if in doubt contact a professional. You'll need the following:

  • Twin-filter respirator mask (Bunnings)
  • Protective Gloves (Bunnings)
  • Bleach (Coles)
  • Baking Soda (Coles)
  • Toilet paper
  • Mixing bowl

Step By Step

Open any windows to allow fresh air flow into the work area.

Put on the mask securely such that it covers your face well and both sets of straps provide a tight fit, then put on the gloves.

Pour some bleach and some baking soda into the mixing bowl and stir (I use a grout brush) until the resulting mixture has a paste-like texture.

Fold up some tissue paper so it is in a long line similar to the area of grout you wish to clean. Dip the tissue paper in the mixture so it is completely soaked, pull it out and squeeze it to remove excess.

Stick the tissue paper containing the mixture along the grout line to be cleaned; if you've done everything correctly the tissue paper will stick both horizontally and vertically and not fall off.

Do as many lines as you wish, then once you are done leave everything in place for at least 30 minutes, longer for areas that are more heavily soiled.

After waiting the required time remove the tissue paper and pop it in the bin. Check out this black mouldy vertical shower grout line in the edge of this shower wall for the results you can expect:

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Finishing It Off

After you have removed and disposed of all the tissue paper lines, it's time to clean all of the shower tiles & grout. We recommend using a citrus, enzyme or pH neutral cleaner from a professional cleaning supply store in Adelaide. Spray it on over the shower tiles, scrub it in, leave it for 5-15 minutes. Then scrub with a wet brush again getting into the grout, after which the area should be completely rinsed with hot water. Finish by drying everything off using microfibre cloths and you should have sparking white shower tiles & grout once again.

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Does Bleach Really Kill Mould?

Some websites write that all the bleach will do is turn the mould white, but that the mould will still be there or will return black quickly after using bleach. This is not entirely true; under prolonged contact on non-porous surfaces such as tiles, bathtubs, glass etc, bleach is lethal to mould and also neutralises any spores or other allergens the mould may produce. Grout is porous so if the mould has penetrated through to the pores it will not be removed, but if it has not it can be removed successfully using this method where other cleaning methods fail.

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Will The Mould Return?

On non-porous surfaces or porous surfaces such as grout where the mould has not penetrated through, we have never observed a job in Adelaide where the mould returned after cleaning, provided a regular shower cleaning & maintenance program is put in place to stop the mould from forming again. Mould typically occurs in showers and grout due to the frequent presence of water and humidity together with a lack of cleaning. Removing the mould and putting in a weekly or fornightly cleaning schedule will get rid of the mould and prevent it from returning again!

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Lemon Juice, Vinegar, Hydrogen Peroxide, Baking Soda, Bleach TIle & Grout Cleaning?

A word about home remedies. Many websites and even some stores & operators in Adelaide recommend home-made recipes including vinegar, peroxide and baking soda for regular maintenance of shower tiles and grout. We advise against these as:

lemon juice and vinegar contain acids which if used to clean grout will etch the grout over time, resulting in pinholes in the surface of the grout where the acid has dissolved away the calcium carbonate in the grout lines. This can give tiles and grout a dull appearance. They can also discolour grout over time and because they are acidic and if your grout has been sealed, can also damage the sealer. Avoid lemon juice, vinegar and anything acidic on natural stones such as travertine, limestone and marble.

hydrogen peroxide and bleach should not be used for regular maintenance cleaning as both can cause any number of issues including discolouration, harm to sealers, coatings/finishers and can corrode or rust metal fixtures. Use only as a last resort and very carefully, and always wear appropriate protective equipment and clothing to protect your skin and breathing.

Grout Sealing

To prevent grout lines from becoming permanently discoloured and make your weekly maintenance tile and grout clean a breeze, a high quality penetrating sealer should be applied to the grout after cleaning. Penetrating sealers bond to the grout and repel water (and water-based stains) and some of the higher quality sealers will also repel oil-based stains. Quality grout sealers bought locally an Adelaide hardware store will last between 3-4 years at which point the grout will need to be re-sealed. To test whether your grout is sealed pour a small amount of water on the grout, count to 10 then wipe it up. If the tested area is darker than the rest then the grout sealer has worn off or was not sealed and a high quality penetrating grout sealer should be applied.