Leaking Pipe Joint? Compression, Push-Fit and Soldered Fixes

First, work out which kind of joint it is

The fix depends on how the joint was made. Dry the joint and the pipe either side with kitchen roll, then watch for the first bead of water. Water runs along a pipe and drops from the lowest point, so the drip on the floor is often a few inches from the real leak.

• Compression: a brass fitting with a hexagon nut on each pipe. It is the usual joint under sinks, on tap connectors, on isolating valves and on older radiator valves.
• Push-fit: a white, grey or black plastic fitting, sometimes brass, with a collar or cap where the pipe goes in and no nut to tighten with a spanner.
• Soldered: a smooth copper sleeve over the pipe, often with a dull silver line of solder at the edge or a ring bulge in the middle. There is nothing to undo.

Stopping a leaking compression fitting

The nut squeezes the olive onto the pipe and into the seat of the fitting. A weep usually means the nut was never quite tight, the olive went on squint, or the pipe has been knocked since. A bead of water under the nut, often with a green or white crust, is the classic sign.

Put one spanner on the fitting body to hold it still and a second on the nut, then tighten the nut by about a quarter of a turn. Holding the body matters: if you let it turn, you twist the pipe and can loosen the joint on the other side.

If a quarter turn has made no difference, stop tightening. An olive that has been crushed too hard deforms and then leaks worse, and on thin copper you can start to squash the pipe itself. The joint needs remaking with the water off: the old olive is cut or pulled off, the pipe end checked, and a new olive fitted. It is a short job with the right tools, and our guide to a leaking pipe under the sink covers the spot where most of these turn up.

Do not wrap a weeping compression joint in PTFE tape or silicone and leave it. Tape round the outside of the nut does not reach the seal, and it hides a leak that is still rotting the cupboard base or the floor underneath.

Why push-fit joints leak

A push-fit joint seals on a rubber O-ring and grips the pipe with a ring of small teeth. The fitting itself is rarely at fault. The causes are usually installation ones, and they often show up months later when the heating comes on and the pipe moves.

• The pipe was not pushed fully home to its depth mark, so it held for a while and then started to drip.
• No pipe insert. Plastic pipe needs a support sleeve in its end so the O-ring has something firm to seal against.
• A scored or badly cut pipe end, which leaves a scratch the O-ring cannot seal over.
• Side load from a pipe bent into the fitting at an angle, pulling the O-ring out of line.

Fixing a leaking push-fit joint

Tightening does nothing to most push-fit joints. With the water off, the pipe is released by pressing the collet in, then recut square with a pipe cutter, given a new insert and pushed home to its depth mark. On fittings with a screw cap, a hand tight turn is sometimes enough, but never put a wrench on it.

Not every fitting is meant to be reused, so if in doubt, fit a new one. Push-fit is a sound system when it is fitted properly, and our guide to copper vs plastic pipes covers where each one makes sense.

A leaking soldered joint

Soldered joints do not loosen the way compression joints do. When one leaks, it is usually because it was a dry joint from the start, with the solder never flowing all the way round, or because leftover flux has slowly eaten a pinhole in the copper just next to the fitting.

There is nothing to tighten. The pipe has to be drained, because solder will not flow with water in it, and the joint remade or cut out and replaced. On a heating pipe that means draining part of the system and repressurising it afterwards.

Epoxy putty and bolt-on repair clamps are fine as a stopgap until then, but treat them as temporary, especially on a hot pipe or anywhere hidden.

Radiator valve and tap connector joints

Radiator valves have two joints each: a compression joint where the pipe comes up from the floor, and a union nut where the valve meets the tail screwed into the radiator. A drip from the union nut can sometimes be stopped with a gentle nip. If it keeps going, the tail needs resealing, which means isolating and draining the radiator, and heating water is usually black, so protect the carpet.

A flexible tap connector that leaks from the braided hose, or whose braid has rusted or bulged, should be replaced rather than tightened. If the leak is from the small valve on the pipe instead, our guide on an isolation valve leaking goes through it. Joints on and around a hot water cylinder are a separate job, because some of them are part of the safety equipment, and our guide to a hot water cylinder leaking covers those.

Why a joint that was fine for years starts leaking now

Joints usually start to weep after something else changes.

• The heating coming on for the first time in autumn, when pipes that have sat cold all summer expand and move.
• A new boiler, cylinder or bathroom, where work nearby has disturbed pipes that were not touched directly.
• High mains pressure, or pressure spikes when a tap or washing machine valve closes quickly. If the pipes also bang, read our guide on water hammer, and a failing pressure reducing valve can raise the pressure through the whole house.
• Old joints on the valve that controls the whole supply. If the leak is at the main valve itself, see our guide to a stopcock leaking.

When the leaking joint is hidden

Joints under floors, in boxing or behind a bath panel show up as a damp patch, a stained ceiling below or a soft floor rather than a drip. On a combi or sealed heating system, pressure that keeps dropping with no visible leak can point to a heating joint under the floor.

Pulling up floors on a guess is expensive. Our leak detection and repair service pressure tests first to prove where the loss is, then uses acoustic, thermal and tracer gas equipment to find the joint, and opens up only that spot. If you are claiming on insurance, our guide on what your insurer means by trace and access explains how that side usually works.

Is a leaking pipe joint an emergency?

A slow weep you can catch in a container is not an emergency, but it should be fixed within days, not months. A constant drip onto a chipboard floor or cupboard base does far more damage than it looks.

Treat it as urgent if the drip is steady or getting faster, if water is spraying, if it is near sockets, lights or a consumer unit, or if water is showing through a ceiling. Turn the water off at the stopcock, and if you are not sure where that is, our guide on where is my stopcock shows the usual places to look. Our guides to water escaping in the house and what to do if water is coming through the ceiling cover the first few minutes. A joint that has split open completely is a burst, and our burst pipe repair page explains what we do on those visits.

Getting a leaking joint fixed

If a quarter turn has not stopped it, the joint is push-fit or soldered, or you cannot see where the water is coming from, call us on 020 4652 5111 or send an enquiry with a photo of the joint and the pipes around it. We have 20 engineers across London, and remaking a joint is usually done in one visit, with the joints nearby checked while the water is off. Our rate is set out on the pricing page and agreed before we attend.