Plumbing Pipe Leak

How to Fix a Leaking Pipe Joint – DIY Guide

ByDIYnut

Plumbing › Pipes

How to Fix a Leaking Pipe Joint

DIY Guide

Stop a dripping pipe joint for good with the right fix first time.

Quick Answer

Fix a leaking pipe joint by isolating the water supply, draining the pipe, drying the joint thoroughly, then tightening or remaking the joint using PTFE tape, jointing compound, or a new compression fitting depending on joint type.

Before: Fix a Leaking Pipe Joint
Before
VS
After: Fix a Leaking Pipe Joint
After
Difficulty
Intermediate
Time
1–2 Hours
Cost
£10–£40
Tools Needed
  • Adjustable spanner
  • Pipe slice or hacksaw
  • Pipe cutter
  • Cloth or dry rags
  • Bucket
  • Torch or inspection light
  • Deburring tool
Materials
  • PTFE tape
  • Pipe jointing compound
  • Compression fitting (matching pipe diameter)
  • Push-fit coupling
  • Pipe repair clamp (emergency use)
  • Replacement olive
  • Flux and lead-free solder (for soldered joints)
How To

Step-by-Step Guide

1

Isolate the Water Supply

Turn off the water supply to the affected pipe before doing anything else. If you have an inline isolation valve on the pipe run, use a flathead screwdriver to turn it 90 degrees. If not, turn off the water supply at the stopcock, usually located under the kitchen sink or where the mains enters the property. Open a nearby tap at a lower point to drain residual water from the pipe — this prevents water weeping back into the joint while you work.

2

Identify the Joint Type

Determine what type of joint is leaking before you decide on a fix — the repair method is different for each. Compression fittings have a nut and olive (a small brass ring) and are tightened mechanically. Soldered (capillary) joints are heated and rely on solder to seal. Push-fit fittings use an internal rubber O-ring and simply push onto the pipe. Check whether the pipe is copper or plastic, as this affects which fittings and repair techniques apply. Our copper vs plastic pipes guide explains the key differences if you are unsure.

3

Dry the Pipe and Joint Thoroughly

Use dry rags and hold a cloth firmly around the pipe to absorb all remaining moisture. Even a small amount of water will prevent jointing compound, PTFE tape, and solder from sealing correctly. If the pipe is still weeping, push a small piece of bread (without the crust) into the pipe — it temporarily absorbs water flow and dissolves harmlessly once the supply is restored. Do not skip this step: a wet joint is the single most common reason a repair fails on the first attempt.

4

Remake or Tighten the Joint

For a compression fitting, use two adjustable spanners — one to hold the body of the fitting, one to tighten the nut — and give it a quarter to half turn further. If it still weeps after retightening, disassemble the fitting completely, slide off the old olive, and fit a new olive with jointing compound applied around it before reassembling. For a push-fit fitting, insert a pipe insert (pipe stiffener) into the end of the pipe if not already present, then push the fitting firmly until it clicks. For a soldered joint, the pipe must be cut back, cleaned, refluxed, and resoldered — if you are not confident with soldering, fit a push-fit or fit a compression fitting instead, which requires no heat.

5

Apply PTFE Tape or Jointing Compound Where Required

PTFE tape is used on threaded joints — wrap it clockwise (in the direction of the thread) three to five times around the male thread before reconnecting. Jointing compound can be used on compression olives and threaded fittings for additional sealing. Do not apply PTFE tape to push-fit or compression joints where rubber O-rings do the sealing — it creates an uneven surface and can cause the joint to leak rather than seal. Fixing a dripping tap uses the same PTFE technique on threaded tap tails, so the skill transfers directly.

6

Restore the Water Supply and Check for Leaks

Turn the water supply back on slowly, allowing pressure to build gradually. Watch the joint closely for the first 60 seconds — do not walk away immediately. Run your finger around the full circumference of the joint and check for any moisture. If a minor weep persists on a compression fitting, tighten the nut by no more than a further quarter turn. If the joint leaks significantly or you cannot stop the weep, the pipe end may be damaged or oval — cut back to clean pipe and fit a new coupling. If you are dealing with a leak near a radiator valve, our guide on fixing a leaking radiator valve covers the specific steps for that fitting type.

Watch Out

Common Mistakes to Avoid

Over-tightening a Compression Fitting Applying too much force crushes the olive out of shape, permanently deforming it so the joint can never form a proper seal. You will then need to cut out the fitting and start again with fresh components, adding cost and time to a job that should have been straightforward. Remaking the Joint Without Fully Drying the Pipe Any water present inside or around the joint prevents PTFE tape and jointing compound from adhering, and stops solder from flowing correctly. The joint may appear sealed initially but will begin weeping within hours once under pressure — you will end up doing the job twice. Reusing a Compression Olive Once an olive has been compressed onto a pipe, it deforms to the exact shape of that pipe end. Reusing it on the same or a new fitting rarely produces a reliable seal. Olives are inexpensive — always fit a new one when disassembling a compression joint, and apply jointing compound around it for extra assurance. FAQ Frequently Asked Questions Can I fix a leaking pipe joint without turning off the mains? No — always isolate the water supply before working on any pipe joint. Working on a live pipe is dangerous, ineffective, and risks flooding. Use an inline isolation valve if one is present, otherwise use the main stopcock. Our guide on how to turn off the water supply shows exactly where to find it.

How do I know if my pipe joint needs replacing or just tightening?

If the joint is a compression fitting that was recently installed or disturbed, a quarter to half turn further with a spanner often resolves the leak. If the joint has been leaking for a long time, or has been overtightened previously, the olive is likely damaged and the fitting needs to be remade with new components.

Will PTFE tape fix a leaking compression fitting?

No — PTFE tape is designed for threaded joints, not compression fittings. Wrapping PTFE around a compression olive or nut creates an uneven surface that prevents the olive from seating correctly. Tighten the nut or replace the olive and use jointing compound instead.

Is fixing a leaking pipe joint something a DIYer can legally do in the UK?

Yes — repairing leaking pipe joints on domestic cold and hot water supply pipes is legal DIY work in England, Wales, and Scotland. Work must comply with the Water Supply (Water Fittings) Regulations 1999. Gas pipework must never be touched by anyone who is not Gas Safe registered, and any notifiable plumbing work connected to a boiler or central heating system should be checked by a WaterSafe-approved plumber.

What is the easiest type of joint to use for a DIY pipe repair?

Push-fit fittings are the most straightforward — no tools, no solder, no heat required. They work on both copper and plastic pipe, are widely available, and can be disconnected and repositioned if needed. Ensure you use a pipe insert (stiffener) inside plastic pipe ends to maintain the pipe’s round profile before pushing the fitting on.

Pro Tip

When remaking a compression joint in a tight space where you cannot get two spanners on simultaneously, apply thread-locking jointing compound to the olive and finger-tighten the nut first, then use a single spanner to bring it up to correct torque — the compound compensates for the marginal extra movement and gives a reliable seal without needing to grip the fitting body. Never rely on jointing compound alone on a badly fitting or damaged olive though; compound seals minor imperfections, not structural failures.

Sources

  • WaterSafe — Find a plumber and water regulations guidance — watersafe.org.uk
  • HSE — Water Supply (Water Fittings) Regulations 1999 — hse.gov.uk
  • Which? — DIY plumbing: what you can and cannot do yourself — which.co.uk
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Safety Notice: Electrical and plumbing work can be dangerous if done incorrectly. In the UK, certain electrical work must comply with Part P of the Building Regulations and certain plumbing work with Part G. If in doubt, consult a qualified electrician (NICEIC/NAPIT registered) or plumber (CIPHE/WaterSafe registered). This guide is for general information only — it is not a substitute for professional advice.

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