Replacing a mixer tap cartridge
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A dripping or stiff single-lever mixer tap usually needs a new cartridge — the ceramic disc mechanism inside the tap body that controls flow and temperature. Cartridges are inexpensive (£5–£30) and replacing one is a straightforward DIY job.
Turn off the water supply at the isolation valves under the sink (slot-head screws on the valve body — turn 90° to close). Open the tap to release residual pressure and drain any water in the supply pipes.
Remove the tap handle: look for a small decorative cap on top (prise off with a flat screwdriver), which hides a screw. Remove the screw, then lift the handle off. The cartridge is now visible inside the tap body — usually a cylindrical brass or plastic component.
Note the orientation of the cartridge before removing it (photograph it). Unscrew the cartridge retaining nut (usually a large hexagonal brass collar around the top of the cartridge) with a spanner. Pull the cartridge straight up out of the tap body.
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Frequently asked questions
How long does a tap cartridge last?
A quality ceramic cartridge should last 10–15 years with normal use. In hard water areas, scale build-up on the ceramic faces shortens this to 5–7 years. Signs of a failing cartridge: increasing stiffness, dripping when fully closed, or erratic temperature control on a mixer.
Are tap cartridges expensive?
Generic cartridges cost £5–£20. Branded cartridges from manufacturers like Grohe, Hansgrohe, or Bristan cost £20–£60. Fitting is straightforward if you can identify the correct replacement — the time investment is usually under an hour for a confident DIYer.
Can I fit a different size cartridge to my tap?
No — cartridge diameter must match the tap body precisely. The most common UK domestic sizes are 35mm and 40mm, but other sizes exist. Forcing a wrong-sized cartridge will either not seal correctly (and drip) or damage the tap body. Always measure or take the old cartridge with you when buying a replacement.