Frozen and Burst Pipes: What to Do and How to Prevent
How to thaw a frozen pipe safely, what to do if a pipe bursts, and the simple winter habits that protect your plumbing in a UK cold snap.
When temperatures plunge, water in pipes can freeze and expand. The freeze itself is not usually where the damage happens. The bigger risk is the thaw, when a split pipe starts to leak and floods the property. Knowing how to react, and how to prevent the problem, saves a great deal of mess and expense.
Signs of a frozen pipe
- No water, or only a trickle, from taps in cold weather.
- Frost visible on exposed pipes.
- Unusual sounds, such as gurgling.
- A frozen condensate pipe causing a boiler to lock out. Do not tamper with the boiler itself beyond reading its display; contact a Gas Safe registered engineer if you need help.
If a pipe is frozen but not burst
- Turn off the stopcock to prevent a flood if the pipe is split. If you need help finding it, see finding and using your stopcock.
- Open the nearest tap so melting water and pressure can escape.
- Thaw gently. Use a hairdryer on a low setting, a hot water bottle or warm towels, starting nearest the tap and working back along the pipe.
- Never use a naked flame or blowtorch. It can start a fire and damage pipes.
- Check for leaks as it thaws, and keep the stopcock off until you are sure it is sound.
If the frozen pipe is out of reach, buried or behind a wall, call a plumber rather than hacking about.
If a pipe has burst
Act quickly.
- Turn off the stopcock and all supply to the leak.
- Switch off electricity if water is near sockets, lights or appliances, if you can reach the consumer unit safely.
- Open all cold taps to drain the system, and run hot taps if the heating is off.
- Collect water in buckets and move valuables.
- Photograph damage for insurance.
- Call a plumber. See emergency plumber costs for what to expect.
Do not use hot taps if a boiler or hot cylinder might be affected without advice.
Where pipes freeze most
- Lofts, where insulation prevents heat reaching pipes.
- Outside walls and external taps. See outside taps.
- Garages, outhouses and unheated cellars.
- Pipes under sinks on exterior walls.
- Properties left empty over winter.
Preventing frozen pipes
Insulate
Lag exposed pipes and tanks in lofts and unheated spaces. Foam pipe insulation is cheap and easy to fit. Keep the loft insulation off the area directly under the tank, but insulate above and around.
Keep heating on
If you are away, leave the heating on low, often set to come on at a minimum temperature so pipes stay above freezing. Leave loft hatches open to let some warmth in if advised.
Fix drips
A dripping tap can freeze and block. Fix it, as covered in fixing a dripping tap.
Drain outside taps
Isolate and drain outdoor taps before winter.
Know your valves
Everyone in the household should know where the stopcock is. Test it before winter.
After the thaw
Look for damp patches, stained ceilings or sudden drops in pressure. A slow leak from a damaged joint may not show until days later. If you are not sure, a plumber can check.
Worked example: the cold snap weekend
A family leaves for three nights in January with the heating off. The loft is lightly insulated and a pipe near the cold tank freezes. On the first morning back there is no water at the kitchen tap. They turn off the stopcock, open the tap, warm the pipe in the loft with a hairdryer on low, and watch for leaks. One joint weeps and they call a plumber. Had they left the heating on at a low setting, the pipe would likely have stayed above freezing. The cost of a short repair is a fraction of the damage a full burst can cause.
A quick winter checklist
| Task | When |
|---|---|
| Insulate loft pipes and tanks | Before autumn |
| Drain or lag outside taps | Early autumn |
| Test the stopcock | Autumn |
| Set heating to a low background setting if away | Before leaving |
| Keep the loft hatch closed unless advised otherwise | Cold spells |
| Check condensate pipe lagging | Autumn |
Special cases
- Empty or second homes. Consider draining the system or asking someone to check weekly. A burst can run for days unnoticed.
- Flats. A frozen pipe in a communal riser is a matter for the building manager, and a burst may affect neighbours.
- Rentals. Tell the landlord or agent immediately, and keep photos and messages. See plumbing in a rental.
- Outbuildings and garages. Water to a garage or shed often has little insulation. Isolate it before winter.
What a plumber checks after a thaw
- Visible joints, especially at bends and near fittings.
- Pressure behaviour once the water is back on.
- Any hidden pipes in walls or under floors.
- The state of lagging and any dripping overflow.
Ask them to explain what failed and what to change. If you are unsure who to call, our page on how to choose a plumber helps.
Frequently asked questions
Do frozen pipes always burst?
No. Many freeze and thaw without damage. The risk is higher with old, brittle or poorly supported pipes, and where the pipe is a rigid type.
Is it safe to use a heat gun?
A hairdryer on low is safer. Strong heat can damage plastic pipe and joints, or start a fire if used carelessly.
Will home insurance cover a burst pipe?
Many policies cover escape of water, but conditions apply, such as keeping the heating on. Check your policy and contact your insurer promptly.