Tap Won't Turn Off? What to Do Right Now

Updated July 2026 · Emergency Plumber Chelsea

Start with the isolation valve, because it shuts off just the one tap and leaves the rest of the home running. Under most kitchen sinks and basins there are two small valves on the flexible or copper pipes going up to the tap, one for hot and one for cold. Most have a slot you turn with a flat-head screwdriver or a coin, and some have a small lever. When the slot or lever is in line with the pipe, the valve is open. Turn it a quarter turn so it sits across the pipe and the flow should stop. If the running water is only hot or only cold, you only need to close that side.

If there is no isolation valve, or it has seized and will not turn, go to the main stopcock. In many Chelsea flats and houses it is under the kitchen sink, in a utility or hall cupboard, or near where the water main enters the building. Turn it clockwise until it stops. Our guide on how to turn off a stopcock covers the details, and if you cannot find yours, see what to do if you can't find your stopcock. In a mansion block the flat stopcock is sometimes in the communal hallway or a riser; our guide to shutting off water in a mansion-block flat explains where to look and when to call the porter or managing agent.

Be aware that a hot tap may not stop when you close the stopcock. In homes with a hot water cylinder fed from a cold water tank in the loft, the hot side is supplied by the tank, not directly by the mains, so closing the main stopcock stops the cold but the hot tap keeps running until the tank empties. On these systems there is usually a valve on the cold feed pipe from the tank to the cylinder, often in the airing cupboard or loft. Close that, or close the isolation valve under the sink, to stop the hot. If you have a combi boiler or a mains-pressure unvented cylinder, the main stopcock stops both.

Do not force the tap harder to make it stop. It is tempting to lean on the handle, but on an old tap that only pushes a worn washer further into a damaged seat, and on a modern ceramic tap it can crack the cartridge or snap the spindle. If turning it firmly closed has not worked, extra force will not either. Isolate the water and leave the tap in whatever position it is in.

Once the water is off, work out what kind of tap you have. A traditional compression tap takes several full turns to go from off to fully on and gets stiffer as it closes, because it squeezes a rubber washer down onto a brass seat. A ceramic disc tap goes from off to fully on in a quarter or half turn and has a firm stop at each end. A single-lever mixer, the kind common in Chelsea kitchens, uses a cartridge that you move up and down for flow and side to side for temperature. Knowing which you have tells you which part has failed.

On a compression tap that keeps running or will not quite shut off, the washer is the usual cause. Over years the rubber hardens, splits or wears into a groove, so it no longer seals against the seat and water gets past however tight you turn it. The fix is a new washer, which is cheap. If the tap still runs after a new washer, the brass seat underneath may be pitted or scored by scale and grit, which is common in hard-water London. A plumber can reseat it with a seat-cutting tool or fit a new tap if the body is badly worn.

On a ceramic disc tap, the tap has two ceramic discs with holes that line up to let water through and turn away from each other to stop it. A tap that will not turn off usually has a cracked disc, a worn seal at the base of the cartridge, or a speck of grit or scale lodged between the discs holding them apart. Sometimes opening and closing the tap a few times with the water isolated and then restored will flush the grit clear, but a cracked or worn cartridge needs replacing. Cartridges are specific to the tap make and model, so take the old one out and match it rather than guessing.

If the handle turns round and round without doing anything, or spins past where it used to stop, the spline on the spindle or inside the handle has stripped, or the headgear has failed. The valve underneath may be stuck partly open. The handle or headgear needs replacing, and on older taps it can be difficult to find an exact match, which is often the point where replacing the whole tap makes more sense. The same applies to a tap whose body is corroded or whose base is leaking as well as running.

A single-lever mixer that will not turn off, or keeps dribbling when the lever is down, almost always has a worn or damaged cartridge. Under the lever, usually behind a small cap and a hex or cross-head screw, the cartridge is held in by a retaining nut. With the water isolated you can take it out and match it. Mixer cartridges vary widely between brands, and some designer taps use parts that have to be ordered, so it is worth knowing the brand before you start. Our guide to a kitchen mixer tap leaking covers the other common mixer faults.

Bath and shower mixers can fail in the same way, but a thermostatic valve that will not turn off may also have a failed internal check valve or thermostatic cartridge, and many are fed by concealed pipework with isolation valves behind an access panel or not at all. If a bath filler or shower will not stop, turn off the stopcock and call a plumber rather than taking a concealed valve apart. An outside tap that will not turn off is covered in our guide to an outside tap leaking or not working.

A tap that will not turn off is urgent if water is overflowing, if you cannot isolate it, or if it is in a flat where water can reach the neighbours below. It is a routine repair if you have isolated it and the rest of the home is working. Either way, do not leave a tap running for hours or overnight while you wait: it wastes a lot of water and, on a metered supply, it shows up on the bill. If it is just a slow drip rather than a running tap, our guide on how to stop a dripping tap covers the simpler fixes.

Emergency Plumber Chelsea repairs and replaces taps that will not turn off across Chelsea, Knightsbridge, South Kensington, Sloane Square and Fulham, including washers, reseating, ceramic and mixer cartridges, headgear and full tap replacements. We explain the options before any work starts, and there is no call-out fee on jobs over 3 hours. See our leaking tap repair and emergency plumber pages, or call 020 3002 6667.

Quick tips

• Close the isolation valve under the sink first: slot across the pipe means off.
• Leave the plug out so a running tap cannot overflow the basin or sink while you sort it.
• On a tank-fed hot water system, closing the stopcock does not stop the hot tap. Use the under-sink valve or the cylinder feed valve.
• Do not force the handle. Extra pressure cracks cartridges and snaps spindles.
• Take the old washer or cartridge with you to the merchant so the replacement matches exactly.

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