Fix a dripping tap and a leaking joint

A dripping tap wastes a startling amount of water, and in a household on stored or collected water that stops being an annoyance and becomes a supply problem. It is also one of the most approachable repairs in the house: a washer costs pence, and the whole job is undoing three things and doing them back up.

The joint half of this page is shorter and matters more, because getting a joint wrong turns a drip into a flood.

Before you undo anything

1. Isolate the water. Either the stop tap, or, much better, the small isolating valve on the pipe under the basin. Most modern installations have one: a slot you turn with a flat screwdriver so the slot lies across the pipe.
2. Open the tap and let it run dry. This proves you have isolated the right thing and drains the pipe.
3. Plug the plughole. Every small brass screw in the world is drawn to an open waste.
4. Put a towel in the basin to catch dropped tools and protect the finish.
5. Have the replacement parts before you start. A tap in pieces at nine on a Sunday evening is not the moment to discover the shop is shut.

See the mains shut-offs if you have not found and exercised the stop tap, and burst pipes if anything goes wrong.

Which tap have you got

Turn it and count. If it takes several turns and feels progressively tighter, it is a washer tap. If it goes a quarter turn and stops dead, it is ceramic.

A traditional tap

1. Prise off the cap on the top of the handle, often a plastic hot or cold disc. There is a screw underneath.
2. Undo the screw and lift the handle off. If it is stuck, penetrating oil and patience; levering with a screwdriver against the tap body will damage both.
3. Undo the headgear nut with a spanner. Hold the tap body steady with your other hand or another spanner, because twisting the whole tap can break the joint below the sink, which turns a drip into a real problem.
4. Lift the headgear out. The washer is on the bottom, held by a small nut or simply pushed on.
5. Replace the washer, matching the size. Take the old one with you.
6. Look at the seat while you are in there: the brass ring the washer presses onto. If it is pitted or scored, a new washer will drip again quickly. A tap reseating tool cuts it flat, or a nylon seat and washer set does the same job without cutting.
7. Reassemble, water back on slowly, and check.

Do not overtighten a washer tap when using it afterwards. The washer seals with light pressure; forcing it closed chews the washer and scores the seat, which is why it started dripping in the first place.

A quarter-turn tap

The same disassembly, and then you replace the whole cartridge rather than a washer.

• Take the old cartridge with you to match it. There are many sizes and they are not interchangeable. Note whether it is hot or cold, because they are handed.
• Some cartridges can be cleaned. Grit and limescale between the ceramic discs is a common cause, and dismantling, rinsing and refitting sometimes fixes it for nothing.
• Refit gently. Ceramic is brittle and cross-threading the housing ruins the tap.

Leaking from the spindle not the spout

A different fault with a different fix, and easy to confuse.

Water appearing around the base of the handle, or under it when the tap is running, is the gland or the O-ring, not the washer.

• On an older tap, tighten the gland nut a fraction. If that does not do it, repack the gland with PTFE tape or gland packing wound into the space.
• On a modern tap, replace the O-rings on the cartridge or spindle. They are cheap and come in kits.
• On a mixer with a swivel spout, water at the base of the spout is the spout O-rings, which are replaced by pulling the spout up and off.

Compression joints

The commonest joint in a British house, and the one most often made worse by good intentions.

How it seals: the nut squeezes a soft copper ring, the olive, between itself and the tapered seat of the fitting. The olive deforms and makes the seal. That deformation is permanent.

A weeping joint:

1. Tighten a quarter turn. No more. Then stop and look for a few minutes.
2. If that fixes it, stop. It usually does.
3. If it does not, do not keep tightening. Past the point of deformation you are crushing the olive out of shape, distorting the seat or splitting the nut, and every one of those turns a weep into a failure when you are not looking.

Doing it properly instead:

1. Water off, drain the pipe.
2. Undo the nut and pull the joint apart.
3. Get the old olive off. Usually it must be cut off with a junior hacksaw, carefully, cutting nearly through and then splitting it with a screwdriver. Do not saw into the pipe.
4. Check the pipe end is round, clean and square. Deburr it.
5. New olive, new nut if the old one is marked.
6. Assemble dry, or with a smear of jointing compound if you have it. PTFE tape wrapped round the olive is a common field fix and is not the correct method, though it works.
7. Nut finger tight, then about a turn and a quarter with a spanner. Hold the fitting with a second spanner so you are not twisting the pipe.
8. Water back on slowly. Watch for five minutes.

Threaded joints and PTFE tape

Wind the tape in the direction the fitting will turn as it tightens. Facing the open end of a normal right-hand thread, that means clockwise. Wound the other way, tightening unwinds the tape and bunches it up, and the joint leaks.

• Five to ten wraps for water, more on a coarse thread.
• Keep it out of the first thread so it cannot be pushed into the pipe.
• Pull it tight into the threads as you wind so it beds in rather than sitting proud.
• Tape plus a smear of jointing compound is belt and braces and is what most plumbers do.
• Never use PTFE tape on a compression joint face as a substitute for a properly seated olive.

Push-fit

Plastic push-fit is the easiest of all and has two failure modes.

• Not pushed fully home. Mark the insertion depth on the pipe with a pencil before assembly so you can see it has gone all the way in.
• No insert. Plastic pipe needs a stiffening insert pushed into the end, and without one the pipe collapses slightly and the O-ring cannot seal. This is the commonest push-fit failure and it is invisible once assembled.
• Cut square and deburr. A ragged or angled cut damages the O-ring on insertion.
• Release with the collet clip, and never reuse a fitting that has been leaking without inspecting the O-ring.

What to leave alone

Also leave alone: anything soldered if you have not soldered before and there is a fire risk in the void, and the incoming main before the stop tap, which belongs to the water company.

Scalding is real. Stored hot water runs at 60 degrees or more and will burn in seconds. Isolate and drain before you open anything on the hot side, and be aware that a length of pipe holds hot water long after the tap has stopped running. See treat a burn.