Why is it still leaking after I tightened it?

The olive has probably deformed, there's debris on the seat, or the pipe isn't fully inserted. Turn off the water, take the joint apart, replace the olive, clean everything and remake it.

Common plumbing problems

Leaking compression fitting: how to stop it

Guidance built with working UK plumbers · Last updated July 2026

A leaking compression fitting usually just needs a careful nip-up of the nut — often a quarter-turn is enough. If tightening doesn't stop it, the olive (the small brass ring inside) has deformed or there's debris, and the joint needs remaking. Whatever you do, don't over-tighten — that splits the olive and makes the leak worse.

Usually amber — manageable, but stop the water before you take it apart. If it's on a live supply pipe, close the isolation valve or stopcock first.

Do this now

Confirm it's a compression fitting — a nut each side of a central body, no solder.
Find the weeping nut — dry it and watch where water reappears.
Isolate the water if it's a supply pipe and you'll be opening it — isolation valve or stopcock.
Nip it up gently — about a quarter-turn with two spanners (one holding the body still so the pipe doesn't twist). Re-test. Don't keep cranking.
Still leaking? Remake it: undo the joint, check/replace the olive, clean the pipe, a smear of jointing compound, reassemble.

Likely causes

Clue	Likely cause
Weeps slightly, never fully tightened	Under-tightened nut
Old joint that's been disturbed	Deformed or work-hardened olive
Leaks straight after assembly	Debris on the seat or pipe not fully inserted
Got worse after tightening hard	Over-tightened — split olive

When to call a professional

Call a plumber for soldered joints, a joint you can't isolate, or if you're not confident remaking a joint under pressure. LeakScan gives guidance, not a substitute for a qualified plumber.

Questions, answered straight

How tight should it be?

Hand-tight, then roughly a quarter to half turn — just until it seals. Over-tightening splits the olive.

Why is it still leaking after tightening?

The olive has likely deformed or there's debris. Turn off the water, take it apart, replace the olive and remake it.

Do I need jointing compound or PTFE?

The olive seals metal-to-metal, so it's not essential, but a light smear of jointing compound helps a remade joint. PTFE is for threads, not the olive.

Can I fix it without turning the water off?

A tiny nip-up can sometimes be done live, but to take the joint apart you must isolate the water first.

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