How to Repair a Leaking Tap: Gasket and Cartridge Step by Step

A leaking tap wastes up to 40 litres of water a day, a leak that shows up immediately on the bill. Yet in most cases, the repair comes down to replacing a gasket worth a few cents or a ceramic cartridge. Here is how to diagnose the leak, choose the right part and carry out the repair yourself in under an hour.

Identifying the type of leak

• Water flows permanently from the spout: the cartridge or the valve is worn
• The tap drips at the base of the handle: the gland packing gasket is faulty
• Water seeps under the sink: the hose fitting is loose or the sealing gasket is crushed
• The handle spins in a vacuum: the fixing screw or the cartridge is broken

A mixer tap (a lever that blends hot and cold water) works with a ceramic cartridge, while a two-handle tap uses valves or screw-in gaskets. It is important to know the type of tap before buying the spare part, because cartridges come in several diameters and models.

The equipment you need

• An adjustable wrench or water pump pliers
• A flat screwdriver and a Phillips screwdriver
• An Allen key (often 3 or 4 mm)
• A clean cloth and a small container
• A new gasket or a cartridge compatible with your tap
• Possibly some penetrating oil if the parts are stuck on by limescale

Replacing the gasket of a two-handle tap

1. Close the water supply valves and open the tap to bleed the pressure.
2. Remove the decorative cap of the handle, then unscrew the screw with the suitable screwdriver.
3. Remove the handle and unscrew the dome (the retaining nut) with the adjustable wrench.
4. Take out the valve and unscrew the screw that holds the rubber gasket.
5. Replace the gasket, coat it with silicone grease and reassemble all the parts in reverse order.

Replacing the cartridge of a mixer tap

1. Close the two water supplies then open the mixer to empty the circuit.
2. Remove the handle (small side screw or cap under the handle) and the escutcheon.
3. Unscrew the retaining nut that holds the cartridge, without forcing.
4. Take out the worn cartridge and compare it with the new one: diameter, notches and height must match.
5. Install the new cartridge aligning the marks, retighten and reassemble the handle.

Checking the seal after the repair

Slowly reopen the stop valves, letting the air escape through the open spout. Then close the tap and observe for a few minutes: a correctly repaired tap no longer lets a single drop through. Run a dry cloth under the fittings to check that no dampness seeps at the base.

The mistakes to avoid

• Replacing the cartridge without having bled the circuit, which causes water to spray under pressure
• Over-tightening the retaining nut and cracking the body of the tap
• Choosing a gasket of a slightly different diameter, which will leak again within days
• Forgetting the silicone grease and forcing the cartridge into its housing

A successful repair shows in everyday life: no more drop tapping in the sink, a handle that turns precisely and a water bill that returns to normal. If the leak persists despite a new gasket and cartridge, the body of the tap is probably cracked: in that case, completely replacing the unit, explained in our dedicated guide, becomes the most economical solution.