Replacing a monobloc mixer tap cartridge
A stiff or dripping monobloc mixer tap is one of the most common kitchen and bathroom complaints — and fortunately, one of the easiest to fix yourself. These single-lever taps are brilliantly convenient until the ceramic disc cartridge inside wears out, usually after 5–10 years of daily use. Hard water, sediment, and general wear gradually degrade the precision-engineered cartridge, leaving you with a tap that's difficult to operate, won't shut off properly, or leaks steadily into the sink. The good news is that replacing the cartridge is a straightforward job that takes 20–30 minutes, costs just £8–£30 in parts, and requires only basic tools. This guide walks you through the entire process, from isolating the water supply to reassembling and testing your tap. If you're uncomfortable working with water fittings or the cartridge proves stuck, calling a qualified plumber is always the sensible choice.
Not sure if this matches your problem?
Use our interactive tool — answer a few questions and get a personalised diagnosis.
Most likely cause & what to check
A monobloc tap has a single lever that controls both temperature and flow. Inside is a ceramic disc cartridge — typically 35mm. When stiff, dripping, or leaking it needs replacing.
Close both isolation valves under the sink. Open the tap to release pressure.
Look for a decorative cap on the handle — prise it off with a flat blade to reveal a screw. Remove the screw, then pull the lever off.
Unscrew the large chrome shroud or collar beneath the lever (hand-tight usually). The cartridge retaining nut is now visible — unscrew it.
Unlock the full step-by-step guide
This guide has more steps written by a qualified plumbing and heating engineer — subscribe to see them all and save yourself a costly call-out.
Frequently asked questions
How do I know if my monobloc tap needs a new cartridge rather than just a clean?
If your tap is stiff, won't fully close, or drips persistently even after you've turned the lever off completely, the cartridge has almost certainly worn out and cleaning won't help. A quick test is to turn off the isolating valves under the sink — if the drip stops immediately, the cartridge is faulty. If you're at all unsure, it's worth trying a cartridge replacement before spending money on a new tap.
Can I replace the cartridge without turning the water off?
Not safely. Always close both the hot and cold isolation valves under the sink and open the tap to release residual pressure beforehand. If your isolation valves are stuck or missing, fit new ones before you start — this is a worthwhile investment that makes future repairs much easier.
What happens if I install the cartridge the wrong way round?
The locating pin on the cartridge will only fit into the body one way, so it's almost impossible to get it backwards. However, if the lever feels reversed (hot on the left instead of right), you may have rotated the cartridge during fitting — simply remove it, rotate 180 degrees, and reinstall.
My cartridge is stuck and won't budge — what should I do?
Try tightening the retaining nut slightly first, then loosen it again — this sometimes breaks the seal. If it remains stuck, apply a penetrating oil like WD-40 around the edges and wait 30 minutes before trying again. As a last resort, wrap a cloth around the cartridge for grip and use gentle leverage, but avoid forcing it as you may damage the tap body.
How do I find the correct replacement cartridge?
Check the markings on your old cartridge — most are branded (Sedal, Kerox, or Galatrek are common). Take the old cartridge to your plumbers' merchant and they'll match it exactly, or order online using the brand and model number. Cartridges are standardised, so an exact match ensures perfect fit and function.