Signs to look for
- Water spraying, pouring or steadily dripping from a pipe, joint or valve
- Water coming through a ceiling, or a ceiling that is stained, sagging or dripping
- Sudden loss of pressure at the taps, sometimes with the sound of running water
- A pipe in a loft, garage or outside wall that has split after freezing weather
What to do first
Turn off the stop tap
Your inside stop tap (stop valve) is usually under the kitchen sink. Turn it clockwise to close it. If there is a small isolating valve on the pipe feeding the leaking fitting, closing that may be enough for a minor leak.
Turn off the heating
Switch the heating off at the controls so the system is not pushing more water around. Do not open up or take the cover off a boiler.
Drain the cold taps
With the stop tap closed, open the cold taps to let the water already in the pipes run away down the sinks instead of through the leak.
Protect and record
Catch water with buckets and towels and move belongings out of the way. Take photos and video of the leak and any damage before you clear up. Your insurer may ask for them.
If water is near sockets, light fittings or the consumer unit, switch the electricity off at the mains only if you can reach the switch from somewhere dry. If you cannot, keep clear and get help. Stay out from under a ceiling that is sagging or bulging with water.
Possible causes
These are common causes, not a diagnosis. The actual fault is confirmed on site.
Frozen pipe
Water expands as it freezes and can split pipes in lofts, garages and outside walls. The leak often only appears once it thaws.
Failed joint or fitting
Compression joints, push-fit fittings and soldered joints can weep or let go, especially if pipework has moved or been knocked.
Damaged pipe
A nail or screw through a pipe, or a pipe crushed under flooring, can leak slowly for some time before it is noticed.
Worn valve or flexible hose
Isolating valves and braided flexible connectors under sinks and basins can perish or fail with age.
How WHP would assess it
- Find exactly where the water is escaping from, which is not always where it shows.
- Check the type and condition of the pipe and fittings either side of the leak, so the repair joins on to sound pipework.
- Explain the repair and any making-good needed before carrying out work.
- Restore the water and check the repair and nearby joints under normal pressure.
We explain any call-out or diagnostic charge before booking, and agree the repair and its cost with you before carrying it out.
What affects the price
Every repair is different, so we do not publish fixed prices for this work. These are the things that make the most difference:
- How easy the pipe is to reach (exposed pipe compared with under floors, behind kitchen units or inside walls)
- Pipe material and size, and the parts needed
- Whether more than one section is damaged
- Whether flooring, boxing or panels need lifting and putting back
Before you call
Useful to send us
- Your postcode
- A photo or short video of the leak and where it is in the property
- Whether you have managed to turn the water off
- Whether water has reached a ceiling, electrics or a neighbour’s property
Get professional help when
- Water is still escaping after you have closed the stop tap
- The stop tap will not turn, or you cannot find it
- Water has reached electrics or is coming through a ceiling
- The leak is on the pipe outside, between the street and your home (see the FAQ below on who is responsible)
Common questions
Which way do I turn the stop tap?
Clockwise to close it. Thames Water advises that the inside stop tap is usually under the kitchen sink. If it is stiff, do not force it with heavy tools. A snapped stop tap can make things worse. Call for help instead.
Who is responsible for a leak on the pipe outside my house?
Thames Water says the supply pipe, which runs from your property boundary into your home, is the homeowner’s responsibility, along with all pipes and fittings inside. Leaks on the communication pipe and water mains in the road or pavement should be reported to your water supplier. If you rent, tell your landlord.
My pipe has frozen but has not burst. What should I do?
Thames Water advises turning off the water at the stop tap, opening the taps, and thawing the pipe slowly with a wrapped hot water bottle or warm towels. Never use a naked flame. Once thawed, check along the pipe for leaks before turning the water back on.
Can I turn the water back on once the leak has stopped?
Leave it off until the pipe has been repaired. A temporary wrap or clamp can reduce a drip but is not a lasting repair.
Sources
Safety and responsibility details checked against these sources on 12 October 2026. Water supplier guidance can change. Check your own supplier’s current advice.