Replace a worn ceramic disc cartridge to stop a dripping tap, working safely with the water isolated throughout.
AB-01Turn off the water and protect the areaTurn off the isolation valve under the tap if there is one - it's usually a small slotted fitting on the pipe, turned with a screwdriver or coin. If there's no isolation valve, turn off the main stopcock (usually under the kitchen sink) and run the tap until the water stops. Put a towel in the sink or basin to catch drips and stop small parts falling down the plughole.
AB-02Remove the tap handleLook for a small cap on top of or behind the handle and prise it off gently with a flat screwdriver. This reveals a fixing screw - undo it and lift the handle straight up and off. Keep the screw and cap somewhere safe, they're easy to lose down the drain.
AB-03Undo the retaining nut and lift out the old cartridgeUnderneath where the handle was, you'll find a retaining nut holding the cartridge in place. Undo it turning anticlockwise with an adjustable spanner, or the tap manufacturer's own spanner if one was supplied. Lift the old cartridge straight out, noting which way round it was facing.
AB-04Match the old cartridge to a new oneCartridges aren't universal - sizes and shapes vary between brands and even between models by the same brand. Take the old cartridge to a plumbers' merchant to match it, or check the tap's brand and model number first. If the tap is old or unbranded, measure the cartridge's diameter and height and take a photo before buying.
AB-05Clean the valve seatingBefore fitting the new cartridge, wipe around the seating inside the tap body with a cloth to clear grit, limescale or old seal debris. A dirty seating is a common cause of a new cartridge still leaking.
AB-06Fit the new cartridgePush the new cartridge into the tap body in the same orientation as the old one. Most have a locating lug or flat edge that only lines up one way, so don't force it - turn it slightly until it drops into place.
AB-07Refit the retaining nut and handleHand-tighten the retaining nut, then nip it up with the spanner - snug, not overtight. Ceramic cartridges crack if forced too hard. Refit the handle, replace the fixing screw and clip the cap back on.
AB-08Turn the water back on and testTurn the isolation valve or stopcock back on slowly. Turn the tap on and off a few times to bed the new cartridge in and check hot and cold both move smoothly. Check under and around the tap base for leaks, and nip the retaining nut a touch tighter if you spot any.
AB-09Tidy upDry the area and remove the towel. Check whether the old cartridge is recyclable before binning it. Wipe down the tap and surrounding surface to finish.
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