PLUMBCRATE
How to fix a leaking compression fitting
Quick answer: most leaking compression fittings are fixed by tightening the nut a further quarter turn. If it still weeps, isolate the water, undo the nut, check the pipe end and olive, and fit a new olive if the old one is damaged or misaligned.
Why compression fittings leak
- The nut has not been tightened enough to compress the olive.
- The olive was fitted squint, or the pipe was not pushed fully home into the fitting.
- The pipe end is oval, scored or has a burr from cutting.
- The olive has been over-tightened and distorted.
- The fitting has been disturbed, for example by an unclipped pipe moving.
Tools and parts
- Two adjustable spanners or grips (one to hold the fitting body, one to turn the nut).
- Replacement compression olives and fittings in the same size as the pipe (15mm or 22mm are the common UK sizes).
- PTFE tape or jointing compound, used sparingly on the olive only if you choose to.
- A pipe cutter and deburring tool if the pipe end needs trimming.
- A towel and container for residual water.
Step by step
- Try tightening first. Hold the fitting body still with one spanner and turn the nut clockwise about a quarter turn with the other. Dry the joint and check after a few minutes.
- Isolate the supply. If it still leaks, turn off the nearest isolating valve or the stopcock, and open a tap to drain the pipe.
- Undo the nut and slide it back along the pipe. Look at the olive: it should sit square and evenly crushed, with no splits or flats.
- Remove a damaged olive. An olive that has been compressed is gripped to the pipe. Use an olive puller, or cut the pipe back just behind it if there is enough slack.
- Prepare the pipe end. It should be round, clean and free of burrs. Cut back with a pipe cutter if needed.
- Refit. Slide on the nut, then a new olive, push the pipe fully into the fitting, and hand-tighten.
- Tighten. For a new olive, a typical guide is hand-tight plus about one full turn with a spanner, holding the body still. Do not overdo it.
- Test. Restore the supply slowly and check the joint with dry tissue. Nip up a little more only if it weeps.
When to replace the whole fitting
Replace the fitting if the body is cracked, the thread is damaged, or it keeps leaking after a new olive. Like-for-like compression fittings come in straight couplers, elbows, tees and tap connectors.
FAQs
Should I put PTFE on a compression olive? It is not normally needed on a correctly made joint. Some installers add a little on the olive to help seal an old or slightly marked pipe. Never wrap the nut thread so heavily that the nut cannot tighten.
Can I reuse an olive? Only if it is undamaged and goes back on the same pipe in the same fitting. If in doubt, fit a new one; they are inexpensive.
Copper or brass olive? Copper olives are softer and the usual choice for copper pipe. Brass olives are harder. Use the type specified for the fitting and pipe.
If the leak is on a gas pipe, do not attempt this repair yourself. Gas work in the UK must be done by a Gas Safe registered engineer.