Tap Leaking Under the Sink: Causes, Checks & Fixes

Isolate the hot and cold supplies before dismantling a tap

Use local service valves or the main stopcock. Do not force seized valves or tap handles. Keep water away from sockets and appliances, and stop if a cracked tap body, failed flexi hose or uncontrolled leak is present.

MOST LIKELY CAUSES

Start with these

Flexible tail leak Braided hoses can fail at crimps or threaded ends.

Compression or valve leak Local pipe joints may drip under pressure.

Water through tap hole A base seal leak can run into the cabinet.

Loose fixing or body seal Movement can disturb hidden connections.

◫ Symptom variations Match the exact tap behaviour before repair. ⌄

Constant drip with tap off
Leak only when tap runs
Braided hose is wet
Water runs down fixing stud
Cabinet becomes wet beneath tap hole

✓ Quick checks Simple checks before removing tap parts. ⌄

Identify whether the fault affects hot, cold or both supplies.
Dry the tap and surrounding area to trace leaks accurately.
Check local isolation valves, flexible tails and visible connections.
Remove and inspect the aerator where flow is poor.
Do not force stiff handles, valves or seized fittings.

If the cause is found: keep the affected supply isolated until the correct repair is completed.

If the leak cannot be controlled: close the main stopcock and call a plumber.

1 Step 1 — Dry all connections Isolate water supplies before dismantling tap components. ⌄

Process

Use tissue around each hose, valve and fixing point.

Success looks like: The first wet point identifies the source.

Escalate when: Water may track from the tap body above.

2 Step 2 — Test hot and cold separately Isolate water supplies before dismantling tap components. ⌄

Process

Run one supply at a time while observing below.

Success looks like: The leaking side is identified.

Escalate when: If the leak is constant, a pressurised connection is faulty.

3 Step 3 — Isolate the affected supply Isolate water supplies before dismantling tap components. ⌄

Process

Close the local valve or main stopcock.

Success looks like: The leak stops.

Escalate when: A damaged hose or valve needs replacement before reuse.

⌁ Common causes explained Why taps drip, seize, leak or lose flow. ⌄

Leaks beneath a tap commonly come from flexible tails, copper connections, isolation valves, fixing studs, cartridge seals or water tracking through the tap hole.

Tap faults often come from small internal seals, cartridges, washers and local restrictions. Water can also track down the tap body and appear under the sink away from the true source.

⌘ Advanced diagnostics Plumber-level checks and repair work. ⌄

Replace flexible tap tails.
Remake compression connections.
Replace leaking isolation valves.
Reseal tap base and tighten fixing kit.
Check tap body and cartridge seals.

▣ Parts that may need replacing Common components linked to this fault. ⌄

Flexible tap tail
Compression olive and nut
Isolation valve
Tap fixing kit
Base seal

! When to call a plumber Conditions that should end basic troubleshooting. ⌄

The local isolation valves will not close or are leaking.
A flexible hose is bulging, split or corroded.
The tap body or pipe connection is cracked.
The tap is heavily corroded or inaccessible.
A thermostatic or pressure-balance fault creates a scalding risk.
The leak or poor flow remains after basic service work.

? Frequently asked questions Common questions about tap faults. ⌄

How do I know whether the tap uses a washer or ceramic cartridge?

Traditional screw-down taps usually use washers. Quarter-turn and many lever taps use ceramic cartridges.

Can I replace a cartridge with any similar-looking one?

No. Height, diameter, spline count and inlet layout must match.

Why is only one side of a mixer tap weak?

That side may have a partly closed valve, blocked hose, inlet filter or cartridge passage.