Tap Won't Turn Off Fully

Stop the water first

Make sure the plug is out and the drain is keeping up, then shut the supply. Do not keep cranking the handle harder: on a ceramic tap that is how the internal stop breaks, and on a washer tap it crushes the washer further.

Look under the basin or sink for small valves on the pipes going up to the tap. These isolation valves have a screwdriver slot or a little handle. Turn the slot or handle a quarter turn so it sits across the pipe, and that tap alone stops. If there are none, or they will not move, go to the main stopcock, usually under the kitchen sink. Our guide on how to turn off a stopcock helps if you cannot find it.

A running hot tap needs one extra thought. If you have a combi boiler or an unvented cylinder with no tank in the loft, hot water comes from the mains, so the stopcock stops it. If you have a hot water cylinder fed from a tank in the loft, the stopcock does not: the cylinder keeps supplying the hot tap. Close the gate valve on the cold feed pipe running from the loft tank down to the bottom of the cylinder, usually a red wheel valve in the airing cupboard or loft. Never turn off the supply to a cylinder and leave the boiler heating it without anyone checking on it; switch the boiler or immersion off too.

What kind of tap do you have?

The fix depends entirely on the mechanism, and the handle tells you which one you have. Open and close it fully and count.

• Several full turns from off to fully on: a traditional compression tap with a rubber washer screwed down onto a brass seat. Common on older basins, baths and outside taps.
• A quarter or half turn with a firm stop at each end: a ceramic disc tap. Two ceramic discs with holes in them rotate against each other inside a cartridge.
• One lever that moves up and down for flow and side to side for temperature: a single-lever mixer with a larger ceramic cartridge, often 35mm or 40mm across.
• The handle turns round and round with no stop and no change in flow: the handle or spindle splines have stripped, whatever the type.

An old tap that keeps running: washer, seat or spindle

On a compression tap, water runs past a closed tap because the rubber washer has perished, split or hardened, or because the brass seat it presses against is pitted and worn. A new washer costs pennies and fits in most taps with a spanner, once the handle and shroud are off. With the supply isolated, open the tap fully to let the pressure out before you undo the headgear. Our guide to replacing tap washers covers the sizes and the order of work.

If a new washer only helps for a few days, the seat is the problem. A tap reseating tool grinds the seat flat again; alternatively, a nylon seat-and-washer kit clips over the old seat. Some taps also have a jumper, the small plate the washer sits on, which can stick and stop the washer following the spindle.

If the handle spins freely and the water carries on, the splines inside the handle or on top of the spindle have been worn round. Sometimes only the handle needs replacing. With the water off, pull the handle and grip the spindle with pliers: if you can close the tap that way, the headgear is fine.

A quarter-turn tap that will not close

Ceramic disc cartridges tend to fail quite suddenly rather than wearing gradually like a washer, usually for one of three reasons. Grit or limescale gets trapped between the discs, most often after mains work in the street or a new plumbing job upstream, and holds them slightly apart. A disc chips or cracks. Or someone forces the handle past its stop and snaps the plastic lug inside the cartridge, so the handle turns but the discs no longer move with it.

Grit can sometimes be cleared. With the water off, undo the cartridge from the tap body, rinse it, open and close it a few times under running water and refit it. If the tap still drips or runs, the cartridge needs replacing.

Cartridges are not universal. They come in different lengths and thread sizes, with different numbers of splines on the spindle, and they are handed: one opens clockwise and the other anticlockwise, so check the direction or buy them as a matched pair. Take the old one to the merchant and match it side by side, or note the brand of the tap. If water is also coming from around the handle, see tap leaking from the handle.

A mixer tap running with the lever off

A single-lever mixer that runs, or drips steadily from the spout with the lever fully down, has a failed main cartridge. These are larger than the cartridges in two-handle taps and are usually specific to the tap manufacturer, so find the brand, often printed on the lever cap or the base, before you shop. Unbranded taps from online sellers can be hard to match, and replacing the whole tap is sometimes the quicker answer.

The replacement follows the same pattern on most mixers: water off, lever cap off, grub screw out, lever off, then the shroud and retaining nut, and the cartridge lifts out. Note which way round it sat, because the locating lugs only fit one way. Our guides to mixer tap leaking and kitchen mixer taps leaking at the base cover the other failure points on the same taps.

If more than one tap in the house starts running or dripping at the same time, or the pipes bang when you shut a tap quickly, the mains pressure may be high and damaging the valves. That is worth checking before replacing cartridges one after another; see water hammer and banging pipes.

When it cannot wait, and what it costs

A tap that will not turn off is urgent when you cannot isolate it: the isolation valves are missing or seized, the stopcock will not shut, or it is a hot tap on a cylinder you cannot isolate. It is also urgent when the drain cannot keep up, or when the tap is a basin in a flat where an overflow would reach the neighbour below. Water running all night on a meter is expensive too; see how much water a dripping tap wastes for the scale.

A plumber isolates the tap, identifies the mechanism and brand, and fits a washer, a pair of cartridges or a new valve, then checks the isolation valves so the next repair is easy. Replacement ceramic cartridges typically cost around £8 to £40 each at a merchant, with branded mixer cartridges at the top of that range or above. Across the London market, a tap cartridge or washer repair is commonly quoted at about £80 to £140 including standard parts. With us the visit is a £60 call-out at any hour, and the repair price is agreed with you on site before any work starts. Book a leaking tap repair if the tap will not stop or you cannot isolate it.