How to fix a dripping tap: washers, ceramic cartridges and mixer taps

Identify your tap

• Compression (washer) tap: the handle turns several times from off to fully on, and you have to tighten it to stop the flow. Inside is a rubber washer pressed against a seat. A drip usually means the washer is worn.
• Ceramic disc tap: the handle turns only a quarter or half turn from off to on. Inside is a cartridge with two ceramic discs. A drip usually means a worn or damaged cartridge, or grit between the discs.
• Single-lever mixer: one lever controls flow and temperature. Inside is a cartridge, usually ceramic. A drip usually means the cartridge needs replacing or its seals have worn.
• Leak from the base or around the spout rather than the outlet is usually a worn O-ring (a small rubber ring seal), not the washer or cartridge.

Tools and parts

• adjustable spanner, screwdrivers (flat and cross-head), Allen keys for many mixer taps
• a cloth to protect chrome from spanner marks
• replacement washer, cartridge or O-rings matched to your tap
• silicone grease suitable for taps, for O-rings
• a plug for the basin so small parts do not disappear down the drain

Isolate the water

1. Look under the sink for an isolation valve on the pipe to the tap. Many have a slot you turn a quarter turn with a flat screwdriver until it is across the pipe.
2. If there is no isolation valve, turn off the main stopcock (often under the kitchen sink or where the supply enters the house).
3. Open the tap to drain the remaining water and confirm the supply is off.

Replacing a washer (compression tap)

1. Prise off the decorative cap on the handle and undo the screw, then pull off the handle.
2. Unscrew the headgear (the large nut-shaped part) with a spanner, holding the tap body steady so you do not twist it.
3. The washer sits at the bottom of the headgear, held by a small nut or simply pushed on. Remove it and fit a new one of the same size.
4. Check the seat inside the tap body. If it is pitted or rough, a new washer may not seal; a reseating tool or a plumber can sort that.
5. Reassemble and turn the water back on slowly.

Replacing a ceramic cartridge

1. Remove the handle as above (some have a grub screw under a cap or at the back).
2. Unscrew the cartridge with a spanner. Note which way it faces: on many taps hot and cold cartridges turn in opposite directions and are not interchangeable.
3. Take the old cartridge to the shop or match the brand and spline count (the number of teeth on the spindle). Fitting the wrong one rarely works.
4. Before replacing, rinse the old one; sometimes grit is the only problem.
5. Fit the new cartridge, hand-tight then a little more, reassemble and test.

Mixer taps and O-rings

When to call a plumber

• you cannot turn the water off, or the stopcock or isolation valve is seized
• the tap body is cracked, or a part is corroded solid and will not move without force
• the valve seat is badly damaged
• you cannot identify or source the parts
• water is leaking under the sink, into a cupboard or through a ceiling
• the tap is old enough that replacing it is likely to be quicker and cheaper than repairing it