For a burst water pipe, the order is: stopcock off, cold taps open to drain, electrics off where water has reached them, then photographs and a call to your insurer. Do not let the heating thaw the pipe with the water still on. If the split is inside a wall or floor, a leak detection survey finds it so one small area is opened rather than several.
Cornwall does not get many hard frosts, which is exactly why a burst catches people out here. A pipe in an uninsulated loft, an outside tap, or a supply run through an unheated porch freezes during a rare cold snap, and the split only shows itself when the thaw comes and the water starts moving again. If you are reading this with water coming through a ceiling, skip to the checklist below and come back to the rest later. If the house is a holiday let or a second home that has been standing empty, the second half of this guide is for you.
The first hour checklist
- Turn off the stopcock. It is usually under the kitchen sink, in a downstairs toilet, in the hall cupboard or where the supply enters the house. Turn clockwise until it stops. If it will not budge or you cannot find it, the outside stop valve at the boundary (in a small chamber near the pavement or gateway) shuts the supply too, and a long-handled key or a pair of grips will turn it. Our guide to finding the stopcock in an older house helps if yours is not in an obvious place.
- Open the cold taps. Start with the lowest one in the house. This drains the pipework and stops the flow through the split within a few minutes. Flush the toilets as well.
- Switch off the heating and hot water. If the house has a hot water cylinder, do not drain it unless a plumber tells you to, but do switch off the immersion heater and boiler so nothing heats an empty vessel.
- Deal with the electrics. If water is coming through a light fitting or near a socket, turn off that circuit at the consumer unit. If you are not sure which circuit, turn off the lot. Do not touch a wet switch.
- Catch the water. Buckets under the drip, towels along the base of walls, and if a ceiling is bulging, pierce it with a screwdriver over a bucket to let the water out before the plasterboard gives way. A controlled hole is a lot cheaper than a collapsed ceiling.
- Photograph everything. The split if you can see it, the water, the damaged floor, the stained ceiling, and the stopcock in the off position. Take a short video too. Your insurer will want evidence, and it disappears as things dry.
- Move what you can. Rugs, furniture, electricals and anything on a floor that is wet. Lift the corner of a carpet so air can get under it.
- Ring your insurer. Most have a claims line and many will send a plumber or a drying company under the policy. Tell them it is an escape of water following a frost. Ask whether the policy includes trace and access cover, which pays towards finding a hidden split and making good afterwards, though not the pipe repair itself.
What not to do
- Do not thaw a frozen pipe with the water still on. Ice can be holding a split closed. Isolate first, then thaw gently with warm towels or a hairdryer on low. Never a blowtorch.
- Do not turn the water back on to see what happens. If the split is hidden, that is another hour of water into the fabric of the house.
- Do not start ripping out plaster to find the split. Water travels a long way along joists and behind plaster, and the wet patch is rarely where the pipe has failed. Speculative holes are the main reason repairs end up costing more than they should.
- Do not throw damaged items away until the insurer has seen them or agreed in writing that you can.
Finding the split when you cannot see it
A frost split is often a clean, short crack along the pipe, and on copper it can be a few millimetres long. If the pipe is exposed in a loft or a cupboard, you will spot it once the water is off and things are mopped. The difficult case is a pipe inside a wall, under a floor or behind a fitted kitchen, where all you have is a wet patch some distance away.
This is where water leak detection earns its place. The methods depend on where the pipe runs:
- Thermal imaging shows the temperature difference where cold water has soaked into a wall or floor, and maps the pipe run when the heating is on.
- Acoustic listening picks up the sound of water escaping under pressure once the supply is briefly restored for the test.
- Tracer gas is introduced into the drained pipe and detected where it surfaces, which works when a pipe is buried in screed or behind tiles.
- Moisture mapping plots how far the water has travelled, which the drying company and the insurer both need.
The result is a mark on the wall or floor saying “open here”, so the plumber cuts one hole rather than four. Our guide to what to expect from a leak detection survey covers how a visit runs.
Empty holiday homes after a cold snap
The worst frost bursts we see are in properties nobody was in. A holiday let in Bude or Perranporth closed for January, the heating off to save money, a cold week, and then a thaw. Nobody arrives for a fortnight. By then the water has been running through the house for days, and the ceiling, the floor and the kitchen have gone.
If you own or manage a property that stands empty in winter:
- Turn the water off at the stopcock when you leave and open a tap to drop the pressure. This alone prevents most disasters.
- Leave the heating on a frost setting, or a timed low temperature, rather than off. Check your policy: many insurers require heating to be maintained or the water drained during unoccupied periods in winter, and a breach can affect a claim.
- Insulate the loft pipes and tank, and the outside tap. These are the places that freeze first.
- Have someone check the property after any cold spell and ask them to photograph the water meter. A meter that has moved with nobody there is the earliest sign of trouble. Our guide to a water meter moving when nothing is on explains what to look for.
- Consider an automatic shut-off valve on the incoming main, which closes the supply if it detects continuous flow.
After the emergency: drying and repair
Once the split is found and repaired, the house has to dry, and in an old Cornish cottage that is slower than people expect. Solid walls, lime plaster and slate floors hold water for weeks, and a rush to redecorate traps moisture that comes back as mould. A drying company under your policy will bring dehumidifiers and take moisture readings until the fabric is back to normal. Keep the readings; they form part of the claim.
For the claim itself, our step-by-step guide on how to claim on home insurance for a water leak covers what to send, what a loss adjuster looks for and how a leak detection report supports the claim. We carry out leak detection across Cornwall and produce that report as standard.
Frequently asked questions
Should I turn the water off if I think a pipe has frozen but not burst?
Yes. Turn off the stopcock and open a cold tap, then thaw the pipe gently from the tap end back towards the frozen section with warm towels or a hairdryer. If the pipe has split, the water will show once it thaws and you will be glad the supply is off.
How do I find a burst pipe inside a wall?
Do not chase the wet patch, because water travels along joists and behind plaster before it shows. Thermal imaging, acoustic listening and tracer gas locate the split to a small area so only one opening is needed. A survey report also supports a trace and access claim.
Does home insurance cover a burst pipe after a frost?
Escape of water is a standard peril on most buildings policies, so the damage is usually covered. Many policies also include trace and access for finding a hidden split. Check the unoccupancy conditions if the house was empty, since insurers often require heating on or water drained in winter.
Can I turn the water back on once the pipe is repaired?
Yes, but slowly. Open the stopcock gradually with a cold tap running to let air out, then walk the house checking each joint and the repair. Watch the water meter with everything off afterwards. If it still moves, there may be a second split elsewhere.
Why did the pipe burst during the thaw and not the frost?
Ice expands and cracks the pipe while it is frozen, but the ice plug also blocks the flow. When it melts, water reaches the crack under full pressure and the leak begins. That is why bursts appear on the first mild morning after a cold snap.
Split pipe you cannot find?
Once the water is off and the panic is over, we can locate a hidden frost split anywhere in Cornwall without tearing the house apart, and give you the written report your insurer needs for a trace and access claim.
