Quarter-turn tap won't turn off — ceramic disc cartridge replacement
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Most likely cause & what to check
Quarter-turn taps (lever handle taps) use a ceramic disc cartridge instead of a rubber washer. The cartridge contains two ceramic discs — one fixed, one rotating — that seal against each other. When they wear, chip, or become gritty, the tap drips or becomes stiff.
Turn off the supply at the isolation valve (under the basin or at the main stopcock). Open the tap briefly to depressurise.
Remove the lever handle: usually there is a grub screw on the underside of the lever accessed with a 2.5mm or 3mm Allen key, or a push-fit cap on top concealing a Phillips screw. Remove the screw and pull off the lever.
Below the handle is a hexagonal cartridge retaining nut — unscrew this anti-clockwise with an adjustable spanner. Pull out the ceramic cartridge — note its orientation (hot taps typically have a left-hand thread; mark top/bottom if unsure).
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Frequently asked questions
Can ceramic disc cartridges be repaired rather than replaced?
The ceramic discs themselves cannot be repaired if chipped or cracked. However, if the cartridge body is intact and the discs are merely calcified with limescale, soaking the cartridge in white vinegar for several hours can restore smooth operation. In hard water areas this may only be a temporary fix — replacement is more permanent.
How do I find the right replacement cartridge for my tap?
Most cartridges have the manufacturer name and size (diameter in mm, usually 35mm or 40mm) stamped on the body. Take the old cartridge to a plumbers merchant, or search the tap brand and model number online. Universal cartridges fit many standard taps but always measure the original first to confirm compatibility.
Is it worth repairing an old tap or should I replace it?
If the tap body is in good condition and the style suits your bathroom, replacing the cartridge (£5–£25) is more economical than a new tap. Replace the whole tap if: it is old and corroded, spare parts are unavailable, or you want to update the style. New quality taps last 20+ years with minimal maintenance.