Start with warm water, a little dish soap and a white nylon pad, and scrub each dark line for a full minute before you reach for anything stronger. Grey grout is often just soap film and dirt, and that comes up at the first step. Move up to a stronger cleaner only when the mild one has failed, and use acid cleaners only on white mineral crust, rarely. If the grout is cracked or crumbling, stop cleaning: no product fixes that.
Five rungs, mildest first
The order below comes from the cement grout care page of LATICRETE, a maker of tile grout. Its point is simple: no cement grout is self-cleaning, and each kind of mark has its own kind of cleaner. Climb one rung at a time and stop at the first one that works.
Before any rung, test the cleaner on a small spot you don't see, behind the shower caddy or low in a corner, and let it dry. The maker asks for this every time, because some cleaners change the colour of grout or dull a tile.
Rung 1: warm water and a nylon pad
Wet the grout, then scrub one line at a time with a white nylon scrubbing pad or a nylon brush for at least 60 seconds. That minute is the maker's figure, and it's longer than most people scrub. Rinse and look again.
Rung 2: a pH-neutral cleaner for everyday dirt
For routine cleaning the maker recommends a clear, pH-neutral cleaner. A few drops of plain dish soap in a bucket of warm water does the same job on most showers. Scrub, rinse with clean water, and dry the lines with a towel so the dirty water doesn't settle back into the joints.
Rung 3: an alkaline cleaner for soap scum and grease
A grey, slightly waxy film on the lower half of the shower wall is usually soap and body oil. That's what alkaline tile cleaners are made for. Read the label for the words alkaline or soap scum, and use one product on its own.
Rung 4: a mould cleaner, or detergent, for black dots
Black or dark green dots that come back in the same corners are mould. Health Canada's bathroom checklist says to remove visible mould by scrubbing with unscented dishwashing detergent and water. The grout maker also lists cleaners made for mould and mildew. Either way, see the safety notes further down first.
Rung 5: an acidic cleaner, for mineral crust only
A hard white crust along the bottom row or around the drain is mineral left by the water, not dirt. Tap water around Vaughan is hard, as our page on bathroom deep cleaning explains, so this is common here. An acidic tile cleaner is the maker's answer for hard-water deposits and other mineral stains. It is not the answer for everyday dirt, so use it now and then, rinse it off well, and keep it away from marble and other stone.
Which rung to start on
| What you see | What it usually is | Start at |
|---|---|---|
| Even grey lines across the floor | Dirt and soap left by water and mopping | Rung 1, then 2 |
| Grey film, a bit slippery, low on the walls | Soap scum and body oil | Rung 3 |
| Black or green dots in corners and near the ceiling | Mould | Rung 4 |
| White, hard crust that feels rough | Mineral from hard water | Rung 5 |
| Orange or pink slime near the drain | A film that grows where water sits | Rung 2, and dry the floor after showers |
| Grout that flakes, cracks or has gaps | Worn or broken grout | No rung. Read the last section |
Mould in the grout: what to keep in mind
Mould is the one mark where people grab the strongest bottle in the house. Health Canada's guide to moisture and mould indoors is direct about it:
Do not use bleach to clean up mould.
The same guide asks that infants, children, seniors, pregnant people and anyone with asthma or another breathing condition stay out of the area while mould is cleaned, and that pets are kept away too. Wear gloves, run the bathroom fan, and open a window if the weather lets you.
If there is bleach in the cupboard anyway, never combine it with anything. Health Canada warns that bleach mixed with products that contain ammonia or an acid, vinegar included, gives off toxic gas. That matters on grout in particular, because rung 5 is an acid.
Popular grout tips, checked against the maker's page
- Pouring neat vinegar or lemon juice on the lines every week puts an acid on grout as routine cleaning. The maker keeps acid cleaners for mineral deposits only, and says acid products aren't recommended on polished marble and most other stone.
- Scouring powder and steel wool feel thorough. The maker's page names a white nylon pad, and says powdered cleanser is not recommended on unsealed or unglazed tile and many types of stone.
- A homemade paste of two or three products is still mixing products. One cleaner at a time, rinsed off before the next, is safer and easier to judge.
- Sealing after every deep clean is advice you'll see everywhere. It depends on the grout. LATICRETE says its own current cement grout does not need sealing, and offers sealers for extra protection. If you don't know what was used, ask whoever tiled the shower before you buy a sealer.
When cleaning is no longer the answer
Grout that crumbles under the nylon pad, lines with gaps, or cracks where the floor meets the wall need repair, not a stronger cleaner. Health Canada's checklist puts it plainly: repair or replace open, cracked or damaged tiles, grout and caulking around showers and tubs. Water that gets behind them is what feeds the mould you keep scrubbing.
Mould that is back within a few weeks of a good clean tells you the same thing. The guide says mould returning after cleaning usually means the moisture source hasn't been dealt with, and that a single patch larger than 3 square metres is a job for a qualified professional.
Keeping the lines light between cleanings
- Run the fan during every shower and for at least 30 minutes after. In November, with the windows shut, this does more than any cleaner.
- Squeegee the walls and the glass after showering. Our piece on cloudy shower glass and hard water covers the door itself.
- Take bottles off the floor and the ledges. The ring under a shampoo bottle is where pink slime and mould start.
- After mopping a tiled bathroom floor, rinse with clean water and dry it. The maker notes that damp mopping leaves dirt in the grout joints.
On our bathroom jobs, shower floor grout is scrubbed line by line with a brush, and there's a short video of it on the before and after page. If the grout, the faucets and the corners all need attention at once, that's the work of a deep cleaning.
