Can I fix a leak under the sink myself?

Often, yes. Loose trap nuts, a perished trap washer and a failed flexible hose are all straightforward homeowner fixes with no specialist tools. A leaking supply-pipe joint under pressure is better left to a plumber.

How much does a plumber charge to fix a leak under the sink?

A simple under-sink fix is typically a minimum call-out or around the first hour of labour, but rates vary by area and time of day. A hidden supply-pipe leak that needs cutting into pipework costs more. Always confirm the price with your local plumber first.

Common plumbing problems

Leak under the kitchen sink: what's causing it and what to do

Guidance built with working UK plumbers · Last updated July 2026

A leak under your kitchen sink almost always comes from one of three places: the waste pipe and P-trap under the plughole, a flexible tap hose, or a compression joint on the supply pipe. Most are low-urgency and fixable yourself in minutes — the trick is finding which joint is wet, then stopping the water at that point.

Usually amber — deal with it calmly, but don't leave it. Standing water damages the cabinet base and the floor. If water keeps coming even with the taps off, it's a supply-side leak — close the isolation valve or your main stopcock now.

Do this now

Clear and dry. Empty the cupboard and dry every pipe and joint with kitchen roll, so fresh water shows up clearly.
Find the source. Wrap a dry piece of tissue around each joint. Run the tap and fill then drain the sink. Watch which tissue wets first — that's your leak.
If it only leaks when water drains → it's the waste/trap. Hand-tighten the trap's plastic nuts (no tools needed). Still weeping? The rubber trap washer has likely perished — a cheap, quick replacement.
If it leaks all the time, even taps off → it's a supply pipe. Close the small isolation valve on that pipe (turn the slot a quarter-turn so it sits across the pipe), or the main stopcock, to stop the flow.
If a braided tap hose is weeping from the braid itself → it can't be tightened. It needs replacing.

Likely causes

What you see	Likely cause
Leaks only while draining	Loose P-trap nut or perished trap washer
Damp at the tap tails, constant	Failed flexible tap hose
Drip at a metal pipe joint, constant	Loose or failing compression fitting
Water around the sink rim, not below	Failed sealant around the sink — not a pipe leak

When to call a plumber

Call a plumber if you can't find or stop the source, a compression or soldered joint is leaking under pressure, or water has already spread into the cabinet base, the floor, or the ceiling below. If you're ever unsure, a professional eye is the safe call — LeakScan gives you guidance, not a substitute for a qualified plumber.

Questions, answered straight

Is a leak under the kitchen sink an emergency?

Usually not — most are slow, low-urgency leaks (amber). It only becomes urgent if water is pouring out and you can't stop it, or it's reaching the floor or ceiling below. If it keeps coming with the taps off, close the isolation valve or stopcock.

Why does it only leak when I run the water?

That points to the waste side — the P-trap and the connections around the plughole only carry water while the sink drains. Hand-tighten the trap nuts and check the washer.

Can I fix it myself?

Often yes. Loose trap nuts, a perished trap washer and a failed flexible hose are all straightforward homeowner fixes. A supply-pipe joint leaking under pressure is better left to a plumber.

How much does a plumber charge for this?

A simple under-sink fix is typically a minimum call-out or around the first hour of labour, but rates vary by area and time. A hidden supply-pipe leak costs more. Confirm the price with your local plumber first.

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