How to Replace a Ceramic Disc Tap Cartridge

Ceramic disc cartridges fail by scoring or clogging, not by wearing a flat rubber washer. Replacing a ceramic disc tap cartridge is the standard fix for a modern lever mixer that drips from the spout. Take the old cartridge with you; brand and spindle size matter more than any “universal” claim on the box.

For the full mixer drip path including O-ring weeps, see how to fix a dripping mixer tap. For a classic rubber washer instead of a cartridge, see how to change a tap washer.

Confirm you need a cartridge

If you see a brass spindle with a rubber disc, stop and follow how to change a tap washer.

Match the cartridge before you buy

Cartridges differ by diameter, height, spline count on the stem, and hot/cold port layout. Photograph the top and bottom of the old unit. Note any stamp on the tap body (brand or model). DIY stores can match from the old part more reliably than from a vague description.

A cartridge that is 1 mm out will either bind or drip. Do not force a “near enough” fit.

Isolate and expose

Close hot and cold isolators, open the mixer to drain, and put the plug in. Photograph the handle angle so you can refit it square. Undo the grub screw (often Allen), lift the handle, and remove the decorative shroud with a cloth-wrapped spanner.

Step-by-step

1. Undo the retaining nut

You should see a nut or collar around the cartridge top. Undo it. Keep the thread clean; grit here scratches the new O-rings on the way in.

2. Lift the cartridge straight up

Pull vertically. Twisting hard can crack a plastic top or score the housing. Note which way the ports faced (or keep your photo handy).

3. Clean the housing

Wipe the seats inside the body. A flake of scale left behind will make a new cartridge drip on day one. Do not gouge the brass with a screwdriver tip.

4. Fit the new cartridge

Light silicone grease on new O-rings helps if the kit allows it (check the instructions). Seat the cartridge in the same orientation. Tighten the retaining nut firmly. Over-tightening cracks cheap cartridge tops.

5. Rebuild and cycle the mixer

Refit shroud and handle. Open isolators slowly. Run hot, cold, and mixed, then shut off fully and watch the spout. Feel around the base for a separate weep.

Mistakes that waste a cartridge

• Buying universal without matching spline and ports.
• Refitting 180° out on mixers that care about orientation.
• Leaving grit in the housing.
• Crushing the cartridge with the retaining nut.

When to call a plumber

Stop if the cartridge is seized solid in a corroded body, if the housing is cracked, or if the tap brand is long discontinued and no part exists. A full replacement is then cheaper: how to replace a kitchen tap or how to replace a bathroom basin tap.

Also in this cluster: how to tighten a loose tap if the body rocks after rebuild, and how to replace a bath mixer tap for bath fittings.

FAQ

How can I tell the cartridge is ceramic rather than a washer valve?

With the handle off, a ceramic cartridge is a sealed cylinder held by a retaining nut. A washer valve is a brass spindle with a rubber disc on the end. If you see rubber on a spindle tip, stop and follow how to change a tap washer.

Are ceramic disc cartridges interchangeable?

Rarely. Diameter, height, stem splines, and port layout must match. Count the splines on the stem and photograph the ports on the underside before you buy. Take the old cartridge to the store rather than guessing from the tap’s appearance.

Why does a brand-new cartridge still drip on day one?

Usually grit left in the housing, a 1 mm wrong part, or ports fitted the wrong way round. Pull it, wipe the seats, confirm the model stamp, and reseat. If the brass housing is scored, replace the tap rather than stacking another cartridge.