Tap Won't Turn Off? How to Stop the Water and Fix the Cause

If a tap won't turn off, the first job is to stop the water, then find which part inside the tap has failed. Turn the isolation valve under the sink a quarter turn, or close the main stopcock if there isn't one. The fault is nearly always a worn washer, a failed ceramic cartridge or a stripped spindle. Each one gives slightly different symptoms, and knowing which you have tells you which part to buy, or whether it's quicker to get a plumber out.

Stop the water now

If the stopcock is seized or you can't find one, read stopcock won't turn before forcing anything. An old stopcock can snap or start leaking if you put a long lever on it.

Work out which type of tap you have

How the handle feels tells you what's inside:

• The handle turns several full turns from off to fully on. This is a traditional compression tap with a rubber washer on a jumper that presses down onto a brass seat.
• The handle turns only a quarter or half turn. This is a ceramic disc tap. Two ceramic discs slide over each other inside a cartridge.
• A single lever controls flow and temperature. This is a mixer with a single cartridge, usually 35mm or 40mm.

Why a tap won't turn off

Worn washer or damaged seat (traditional taps)

The washer hardens and wears with use, and eventually can't seal against the seat. The first sign is usually a drip that gets worse, then a tap you have to crank hard to stop, then one that won't stop at all. If the seat itself is pitted or scaled, a new washer won't seal either. The seat has to be reground or the headgear replaced. Our guide to fixing a dripping tap covers washer replacement step by step.

Worn or cracked ceramic cartridge (quarter-turn and mixer taps)

Ceramic discs don't wear like rubber, but grit from the mains, limescale or a chip in the disc face stops them closing fully. The tap turns to its normal off position but water keeps running, often as a steady stream rather than a drip. The fix is a new cartridge. Cleaning the old one occasionally helps where scale is the cause, but a chipped disc can't be repaired.

Stripped spindle or splines

If the handle spins round without getting tighter, the splines on the spindle or inside the handle have worn smooth. The handle is no longer turning the valve. Sometimes only the handle has stripped and a new handle fixes it. More often the headgear or cartridge needs replacing.

Grit or debris after work on the mains

If the tap started running straight after the water was off for repairs, a piece of grit may be lodged under the washer or between the discs. Water supplier notices of work in the street are a common trigger. Taking the cartridge or headgear out and flushing it often clears it.

How to fix it

1. Isolate the tap and open it to drain what's left in the pipe. Put the plug in so small parts can't drop down the waste.
2. Remove the handle. Prise off the cap or indicator disc, undo the screw beneath, and lift the handle off. On lever mixers there is often a small grub screw at the back or underneath.
3. Unscrew the headgear or cartridge with a spanner. Hold the tap body steady with your other hand so the tap doesn't twist on the basin.
4. Inspect and replace. On a compression tap, replace the washer and check the seat for damage. On a ceramic tap, fit a matching cartridge. Take the old part with you to the merchant, as spline counts, lengths and thread sizes vary.
5. Reassemble, turn the water back on slowly and check for drips at the tap and at the isolation valve.

If it's the hot tap

Isolating a hot tap depends on how your hot water is supplied:

• Combi boiler or unvented cylinder: the hot water comes from the mains, so the isolation valve under the sink or the main stopcock will stop it.
• Hot water cylinder fed from a tank in the loft: closing the stopcock won't stop the hot tap quickly, because the cylinder is fed from the tank. Look for a gate valve on the cold feed pipe going into the top or side of the cylinder and close that.

If hot water is running and you can't stop it, switch off the boiler or immersion heater too, so you're not heating water that's going straight down the drain.

When to call a plumber

Call a plumber if you can't isolate the tap, the stopcock or isolation valve won't turn or starts leaking, the tap body is corroded or loose on the basin, you can't identify or buy the right cartridge, or the tap is a concealed or wall-mounted design where the valves sit behind tiles. It's also worth calling if more than one tap is failing, as that can point to high water pressure or scale throughout the system.

We carry out tap repairs and kitchen tap repairs across London, including fitting isolation valves so the next problem is easier to deal with. When you call, tell us whether it's the hot or cold side and what type of tap it is, and a photo helps. Our labour is £95 an hour, the £60 call-out is waived when the job runs over 2 hours, and we confirm the price before any work starts. If water has already got into cupboards or ceilings, see our guide to a leaking stopcock and our water leak repair service.

Frequently Asked Questions