Frozen pipes — how to thaw safely and prevent bursts
⚠️ Do not use a blowtorch to thaw frozen pipes — you risk starting a concealed fire in the building fabric, cracking cast iron or plastic pipes, and melting solder joints. Never leave a heat source unattended on pipework.
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Most likely cause & what to check
Frozen pipes are most common in unheated spaces: loft space (especially roof space water storage tanks and rising mains), garages, outbuildings, pipes in external walls, and condensate drain pipes on boilers during cold snaps.
First turn on the tap supplied by the frozen pipe — as you thaw the pipe, water needs somewhere to go. Leave it open throughout.
Locate the frozen section: look for the part of the pipe closest to an unheated external wall or exposed to the coldest air. Frost-affected pipe sometimes looks slightly deformed or has visible condensation or ice on the outside.
Apply gentle heat starting at the tap end of the frozen section and working back toward the cold area: a hairdryer on medium heat is ideal — keep it moving and do not concentrate on one spot. Warm (not boiling) water poured over the pipe also works well. Hot water bottles and electrician's heat guns (on low) are acceptable alternatives.
Once flow is restored, check immediately for any bursts — a frozen pipe that has split will begin to pour water the moment it thaws. If you find a burst pipe, turn off the mains stopcock immediately.
Prevent recurrence: insulate the vulnerable section with foam pipe lagging (Armaflex or similar, sold in 1m lengths at any DIY store — £1–£3 per metre). For loft pipework, ensure the loft hatch is insulated and close it during cold weather. Leave the loft heating slightly on during a severe frost.
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Frequently asked questions
How do I know if I have a frozen pipe?
Signs include: no water from one or more taps when others work fine, unusual gurgling when other taps run, frost visible on an external pipe, or a bulge in a pipe indicating ice expansion. Act quickly — a frozen pipe can burst within hours of thawing if the ice has already cracked the copper.
What should I do immediately if a frozen pipe bursts?
Turn off the mains stopcock immediately. Open all taps to drain the pipes. Turn off the central heating. If water is near electrics, turn off the consumer unit. Mop up water promptly to minimise damage. Call a plumber to repair the burst section — do not try to solder or repair while the system is wet.
How can I prevent pipes from freezing in winter?
Lag all external and loft-space pipework with foam pipe insulation (£2–£4 per metre). Keep the heating on low (minimum 12°C) when away in winter. Know where your stopcock is. If you're away for more than a few days in cold weather, drain the system entirely or have someone check the property.