Grout is porous cement — it absorbs soap scum, grease, and mould spores with no effort at all, and gives them up only reluctantly. The mistake most people make is reaching for a scrubbing brush immediately, before giving any cleaning agent time to do its job. The secret to cleaning grout efficiently is dwell time, not elbow grease.

Here are four methods in order of intensity — start with the lightest and escalate only if needed.

Method 1: Baking Soda + Vinegar (Light Discolouration)

Mild

Best for: light yellowing, general dullness

Make a paste of baking soda and water. Apply it along the grout lines and leave for 5 minutes. Spray with white vinegar — it will fizz as it reacts. After the fizzing stops (about 30 seconds), scrub with a stiff-bristle brush or old toothbrush, then rinse thoroughly. Effective on recent discolouration, less so on years of buildup.

Method 2: Oxygen Bleach (Moderate Staining)

Moderate

Best for: grout that hasn't been deep cleaned in months

Oxygen bleach (sold as Napisan, OxiClean, or similar) is colour-safe, fume-free, and effective on organic staining. Mix a tablespoon of powder with enough water to form a paste. Apply to grout, cover with cling film to prevent it drying out, and leave for 30–60 minutes. Scrub and rinse. This method works significantly better than most people expect.

Method 3: Hydrogen Peroxide (Stubborn Staining)

Moderate–Strong

Best for: brown or black grout that resists lighter methods

Apply 3% hydrogen peroxide (available at chemists) directly onto the grout lines and leave for 15–20 minutes. Scrub with a brush, then rinse well. For extra strength, mix hydrogen peroxide with baking soda into a paste — the combination is particularly effective on mould-stained grout in showers.

Method 4: Grout Pen or Re-grouting (Permanent Discolouration)

Cosmetic Fix

Best for: grout that is clean but permanently stained

Some grout — particularly in older bathrooms — is stained at a structural level and cannot be restored by cleaning alone. A grout pen (available at hardware stores) coats the grout line with white or coloured paint that restores appearance for 12–18 months. For a permanent fix, a tiler can re-grout, which is less expensive than most people expect for a single shower or splashback.

Keeping Grout Clean Longer

  • Seal it. After a deep clean, apply a grout sealer (around $15–$25 at hardware stores). It creates a protective barrier that makes future cleaning much easier. Reapply annually.
  • Squeegee after every shower. Removing surface water takes 20 seconds and is the single most effective way to prevent soap scum and mould from building up in grout.
  • Weekly spray. A weekly spray of diluted white vinegar (50/50 with water) on shower tiles, left for a few minutes before rinsing, prevents most mineral and soap buildup from ever setting.
  • Fix ventilation. Most shower mould isn't a cleaning problem — it's a ventilation problem. If your bathroom doesn't have a functional exhaust fan, mould in grout will keep coming back regardless of how often you clean it.
End of tenancy tip: Property managers specifically check grout lines in bathroom and kitchen tiles during final inspections. Dark or mouldy grout is one of the most common reasons bonds are reduced. If standard cleaning isn't restoring the grout, try oxygen bleach paste left overnight under cling film — it's the most effective home method for heavily stained grout.

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