How to Deep Clean a Bathroom in a Hard Water Area (A London Guide)

A bathroom deep clean in London is really three separate jobs wearing one name: descaling, degreasing, and dealing with mould. They need different products, they have to happen in a particular order, and doing them in the wrong order is why so much bathroom cleaning feels like effort with nothing to show for it.

If you've scrubbed a shower screen until your arm ached and it still looks cloudy, you weren't doing it wrong exactly. You were using the wrong chemistry.

Why London bathrooms are harder work than most

This isn't in your head. Thames Water draws heavily on groundwater that has passed through chalk, and their own guidance states plainly that all the water in their region is hard. On their scale, anything above 200 mg/l of calcium carbonate counts as hard, and above 300 mg/l as very hard.

What that means in practice is that every time water evaporates off a surface in your bathroom, it leaves the minerals behind. Taps, screens, tiles, shower heads, the inside of the kettle, the bottom of the loo. Given a few months it stops being a film and becomes a crust that has bonded to the surface.

Limescale is calcium carbonate. It is a mineral. You cannot degrease it, because it isn't grease, and scrubbing at it with a cream cleaner mostly polishes it. It needs an acid to dissolve it, and then it comes away almost on its own.

That single fact changes how you clean a London bathroom.

The order that actually works

Work top to bottom, and dry to wet, and do the chemistry before the elbow grease.

1. Clear the room. Everything off every surface. Bottles, bins, mats, toothbrush pots, the lot. You cannot deep clean around objects and half the grime is under them anyway.

2. Dry dust first. Extractor grille, light fitting, the tops of door frames, the trim above the tiles. Do this before anything is wet, or you turn dust into a smear you'll be chasing for an hour.

3. Apply your descaler and walk away. Screen, taps, tile faces, shower head, the waterline in the loo. Dwell time is the whole trick. Ten to fifteen minutes of a product sitting on limescale does more than ten minutes of scrubbing, and it does it without scratching anything.

4. Degrease the different surfaces. Soap scum is not limescale. It's a fatty residue from soap reacting with the minerals in hard water, and it needs an alkaline cleaner, not an acid. This is the bit people miss: a shower screen usually has both, in layers, which is why one product alone never quite finishes the job.

5. Then the mould. Silicone seals, grout lines, the corners behind the bath.

6. Rinse everything, and dry everything. Drying is not optional in a hard water area. Water left to evaporate is how the scale got there in the first place.

7. Floor last, working backwards out of the room.

Descaling without ruining the surface

Acid dissolves limescale. Acid also attacks a lot of the things limescale sits on, which is where bathrooms get damaged.

Safe with a mild acid: glass, ceramic tiles, porcelain sanitaryware, chrome and stainless steel taps.

Not safe: natural stone. Marble, limestone and travertine are calcium carbonate too, which is exactly why acid works on scale, and exactly why it eats the stone. The British Geological Survey describes how limestone rocks dissolve when attacked by rainfall or groundwater that is acidic, and marble is simply limestone that has been recrystallised under heat and pressure. Put a limescale remover on a marble shower tray and you will get a permanent dull patch called an etch. No amount of later cleaning brings it back. It needs polishing out, which is a job for hard floor and stone polishing specialists rather than a cloth.

Also careful with: brushed or matt black taps and unlacquered brass, where acid strips the finish. Test somewhere hidden first, always.

One more thing. Never mix an acidic limescale product with bleach. The combination releases chlorine gas, in a small room, with the door shut. It is the single most common way people hurt themselves cleaning a bathroom.

The shower head trick

Unscrew it, drop it in a bowl of descaler overnight, refit it in the morning. Every jet clears, the spray pattern comes back, and it takes about ninety seconds of actual work.

If it doesn't unscrew, a freezer bag of descaler cable-tied around the head does the same job in place.

Black grout, black silicone, and telling them apart

This is the question we get asked most, and the answer is genuinely useful.

Silicone is the flexible bead where the bath or tray meets the tile. When mould gets into silicone it grows inside the material, not on it. You can bleach the surface and it will lighten for a fortnight, then come back looking identical, because you never reached the growth. Mouldy silicone is a replacement job. Cut it out, clean the channel, reseal. It is a fifteen-minute job that people spend two years scrubbing instead.

Grout is the hard cement-based filler between tiles. It is porous. Mould can grow in it, but it can also just be dirty, and the two look similar from a distance. Grout usually responds to a proper treatment with dwell time, and often comes back further than people expect. Sometimes it doesn't, and if a tenancy has left the grout stained through, the honest answer is that it can be improved rather than made new. We say that on the day rather than after taking the money.

It is worth saying that mould in a bathroom is not only a cosmetic problem. The government's consolidated guidance on understanding and addressing the health risks of damp and mould in the home, published after the coroner's report into the death of Awaab Ishak, sets out both the health risks and what landlords are expected to do about them. If you're a landlord and mould is recurring in a property rather than being a one-off, cleaning is the wrong tool. Ventilation and the underlying cause are the tools.

The bits everyone forgets

After a few hundred bathrooms you learn where the marks are lost.

• The extractor. Take the cover off. There is a decade of felt in there.
• The underside of the toilet seat hinges. The single most reliable place to fail a check-out inspection.
• The waterline inside the pan, which is scale, not staining, and comes off with an acid and a pumice stick.
• The overflow hole in the basin and bath.
• Behind the pedestal, and the wall directly behind the loo.
• The shower door runners and the bottom seal, where black gunk lives.
• The tops of the tiles where they meet the ceiling, and the trim.
• The plughole, properly, not just the visible bit.

When a deep clean isn't the answer

We'd rather tell you this than take a booking.

If the sealant is mouldy, it needs replacing, not cleaning. If a wall is damp because of a leak or a cold bridge, the mould will return regardless. If the grout has been stained through years of a heavy tenancy, expect improvement, not perfection. If the enamel on an old bath has gone porous and dull, that's the enamel failing, not dirt.

What a deep clean genuinely fixes is scale, soap scum, surface mould, grease, and the accumulated grime a weekly wipe never gets to. That covers most bathrooms most of the time.

When people actually book one

Almost always at a turning point rather than as maintenance.

The end of a tenancy is the big one, and bathrooms carry more weight than their size suggests at a check-out inspection. Our end of tenancy cleaning service treats the bathroom and the oven as the two rooms that decide the outcome, and there's more on that in our end of tenancy cleaning checklist.

After that: before a sale or a viewing, after building work when everything is coated in dust, or when a landlord takes a property back and needs it reset before new tenants walk in. That last one is most of what our landlord and letting agent cleaning work involves.

And sometimes it's just that the limescale won and someone wants their bathroom back. That's a perfectly good reason.

FAQ

How long does a bathroom deep clean take? For a standard London bathroom, two to four hours for one cleaner, depending on how much scale and mould there is. A large family bathroom or an en suite with a big glass screen can run longer. Dwell time is part of it, so a quick job is usually a shallow one.

How often should you deep clean a bathroom? In a hard water area like London, once or twice a year, on top of your own wipe-round, is enough to stop scale ever getting a grip. Leaving it three or four years is what turns a straightforward job into a difficult one.

Does white vinegar remove limescale? It does, slowly, because it is a weak acid. It struggles with thick deposits and it comes with the same restrictions as any acid, so keep it away from natural stone, and never combine it with bleach. Purpose-made descalers are stronger and rinse out more cleanly.

Can black mould in grout be removed permanently? It can usually be removed. Keeping it away is about moisture, not cleaning, so it depends on ventilation, how long the extractor runs, and whether the room dries out between uses. Mould in silicone specifically is a replacement job rather than a cleaning one.

Is a bathroom deep clean worth it before a check-out inspection? In our experience it is one of the highest-value hours you can spend on a property. Bathrooms and kitchens are where inventory clerks slow down and look properly.

What's the difference between a deep clean and a normal clean? A normal clean is surfaces. A deep clean is behind, under, inside and into: fittings come apart, seals and runners are worked individually, scale is dissolved rather than wiped, and nothing is cleaned around.

Getting it done properly

If your bathroom has reached the point where a normal clean isn't touching it, one thorough visit resets the room. We price on what's actually there, after seeing it, with a fixed quote up front.

Get a free, no-obligation quote, call 07375 104665, or message us on WhatsApp at wa.me/447375104665.

Last updated: 7 August 2026

About Techno Clean: a London deep-cleaning company covering North London and the Hertfordshire borders. We specialise in one-off deep cleans, end of tenancy and after builders cleaning, fully insured with £5 million public liability cover and DBS-checked teams, rated 4.9 from over 180 reviews across 500+ completed jobs.