A screaming or screeching noise from a bathroom tap puts most people on edge long before it does any real damage. That was exactly the call we took on a recent plumbing job in Belgravia, SW1. The customer described a weird, loud sound every time they turned on the bathroom mixer tap, and understandably assumed something serious was going on behind the wall.
Once our plumber had a look, the cause turned out to be far simpler than the customer feared. A worn cartridge inside the tap, the small component responsible for mixing hot and cold water as you turn the handle, had started to fail. Rather than pull out the whole tap and fit a new one, we replaced just the cartridge. That decision alone saved the customer a significant amount of money.
This kind of plumbing fault is more common than most homeowners realise, and it gets misdiagnosed all the time. Here is what actually causes it, how we tracked it down, and what a similar job usually costs.
Why a Mixer Tap Starts Screaming or Whistling
Inside almost every modern mixer tap sits a cartridge. It controls the flow and blend of hot and cold water as you lift, turn or push the handle. Ceramic disc cartridges are the most common type fitted in UK bathrooms today, and they are designed to last for years without attention.
Problems creep in gradually. Limescale builds up on the ceramic discs, especially in areas with harder water, and the discs start to stick rather than glide smoothly. Rubber seals inside older cartridges can also perish over time. When water gets forced through a narrow, uneven gap instead of a clean opening, it vibrates. That vibration is what produces the whistling, screeching or rattling sound customers report.
Most people assume the noise means a problem elsewhere. Common guesses include an airlock, a failing boiler pump, or loose pipework banging behind the wall. Sometimes it is one of those things. On this job it was not, and that is precisely why a proper diagnosis matters before anyone starts taking pipework apart unnecessarily.
How We Diagnosed the Fault
Our plumber started with the simplest test available. He ran the hot tap alone, then the cold tap alone, then both together. The noise appeared only when both were running and being blended, which pointed straight at the mixing mechanism rather than the supply pipes.
Next, he checked water pressure at the tap and compared it with other outlets in the property. Even pressure across the flat ruled out a wider plumbing system issue. That narrowed the fault down to the tap itself, and specifically to the cartridge doing the mixing work inside it.
Isolate the Water Supply
Before touching anything, our plumber shut off the isolation valves feeding the tap. Most Belgravia properties built in the Victorian or Edwardian period have had isolation valves added under the basin at some point, which makes this step quick. Where valves are missing or seized, we sometimes need to isolate at the stopcock instead.
Strip Down the Tap Handle and Body
With the water off, he removed the handle cap, unscrewed the retaining screw, and lifted the handle away. Underneath sits the cartridge housing, usually held in place with a locking nut or retaining clip depending on the tap manufacturer.
Remove and Inspect the Cartridge
He drew the old cartridge out and inspected it closely. Scale deposits coated the ceramic discs, and one of the seals had started to split. That combination explained both the noise and the slightly stiff action the customer had also mentioned when turning the handle.
Fit the Correct Replacement Cartridge
Getting the exact replacement matters here. Cartridges are not universal, and fitting the wrong size or thread pattern leads to leaks or a handle that will not sit correctly. Our plumber matched the cartridge to the tap brand and model before fitting the new one and reassembling the tap body.
Test Under Full Pressure
Once reassembled, he turned the water back on gradually and ran hot and cold together at full pressure. No noise, no drips from the handle, and smooth mixing across the full range of the tap. The whole repair took a fraction of the time a full tap replacement would have needed.
Plumbing Costs to Expect for This Type of Repair
Our plumbing rate is £90 per hour plus VAT, which comes to £108 including VAT at the current rate of 20%. A straightforward cartridge replacement like this one typically takes between one and two hours once the tap is isolated and stripped down, so labour usually falls somewhere between £108 and £216 including VAT. Replacement cartridges themselves generally cost between £20 and £80 depending on the tap brand, with some designer or older discontinued taps needing a slightly more specialist part.
Compare that with a full mixer tap replacement, which on a similar London job typically runs from £250 to £600 or more including the tap itself, once you account for supply and fit on a period bathroom where pipework may need adjusting. That gap is exactly why a proper diagnosis before assuming the worst pays off. If your tap is making a similar noise, it is always worth getting a qualified plumber to check the cartridge before agreeing to a full unit swap.
When a Noisy Tap Signals a Bigger Plumbing Problem
Not every noisy tap is this simple. Banging pipework, known as water hammer, usually points to a different cause, often unsecured pipe runs or a faulty arrestor. A screeching noise that follows you around the whole flat, rather than one specific tap, can point to failing valves elsewhere in the system.
If you are ever unsure whether the fault sits with the tap or the wider system, get someone qualified to look before reaching for a wrench. Our team handles general Plumbing Services across Belgravia and the surrounding areas, and we always check the simplest explanation first rather than assuming the expensive one. For jobs where a bathroom fault turns out to involve wiring, such as an extractor fan or heated towel rail circuit, we can also bring in our Electrical Services team on the same visit.
Any replacement cartridge or tap fitted in a UK property should meet the requirements set out by the Water Regulations Advisory Scheme. Fitting non-approved parts can affect water quality and, in some cases, invalidate insurance if a fault later causes a leak. If you are ever unsure whether a part is compliant, ask your plumber to confirm before it goes in.
Practical Tips If Your Tap Starts Making Noise
Turn the tap off fully between uses rather than leaving it slightly open, as a partly open cartridge wears faster. If you notice the noise only getting worse, or the handle becoming stiff to turn, book someone in before the cartridge fails completely and leaves you with a tap that will not shut off. In hard water areas, an occasional limescale treatment on aerators and cartridges extends their life considerably. For anyone tackling wider bathroom snagging alongside a tap fault, our Handyman Services team can often deal with several small jobs in the same visit, which saves on call-out costs.
Frequently Asked Questions
Q1: How much does it cost to fix a noisy mixer tap in London?
For a straightforward cartridge replacement, expect labour of roughly £108 to £216 including VAT at our standard plumbing rate of £90 plus VAT per hour, plus a cartridge costing £20 to £80 depending on the tap brand. A full tap replacement on a similar job typically costs £250 to £600 or more including parts and fitting.
Q2: How long does a tap cartridge replacement usually take?
Once the water is isolated, most cartridge replacements take between one and two hours from start to finish. Older taps with seized fittings or a cartridge that is no longer stocked can occasionally take longer while the correct part is sourced.
Q3: Can I replace a tap cartridge myself?
It is possible if you are confident with basic plumbing and can correctly identify the cartridge type, but getting the wrong part or overtightening the housing is a common mistake. In older Belgravia and Kensington properties with original pipework, isolation valves can be stiff or missing entirely, which is where a qualified plumber earns their fee.
Q4: Are there regulations covering replacement taps and cartridges?
Yes. Any fittings used should meet the Water Fittings Regulations enforced through the Water Regulations Advisory Scheme, which covers materials and installation standards for anything connected to the mains water supply. Using non-approved parts can affect water quality and may cause problems if you later need to make an insurance claim.
Q5: How do I know if the noise is the tap or something else in my plumbing?
Run the hot and cold taps separately, then together. If the noise only appears when mixing, it usually points to the cartridge rather than the wider system. Banging that follows through several taps or happens after a boiler fires up generally points to water hammer or pressure issues elsewhere.
Q6: Why does this happen more in some parts of London than others?
Areas with harder water see faster limescale build-up inside ceramic disc cartridges, causing them to stick and vibrate sooner. Belgravia and much of central London sit in a moderately hard water zone, which is why cartridge wear tends to show up earlier here than in soft water regions.
Q7: What happens if I ignore a noisy tap?
The cartridge will keep wearing until it either seizes, leaks internally, or fails to shut off the water fully. At that point what would have been a simple cartridge swap can turn into a tap that needs full replacement, along with possible water damage if a seal gives way overnight.
A screeching tap rarely means what people fear it means, and this Belgravia job is a good example of why it pays to get the actual cause checked before paying for a full replacement. If you have got a tap, radiator or pipe making a noise it should not be making, get in touch with our team through Kensington Maintenance Services and we will send a plumber who will diagnose it properly rather than guess.