Thaw a frozen pipe safely

Find your stopcock, turn off the water, then thaw a frozen pipe gently from the tap end outwards.

TP-01Find and test your stopcock firstBefore you touch anything, find your main stopcock. It's usually under the kitchen sink, sometimes in a cupboard, cellar or utility room. Turn it clockwise a quarter turn and back to check it isn't stiff or seized, so you can shut the water off fast if a pipe has already split.

TP-02Turn off the water supplyTurn the stopcock fully clockwise to shut off the water. Open the lowest cold tap in the house to drain water out of the pipework and relieve pressure. This limits damage if the frozen section has already cracked and only shows once it thaws.

TP-03Find the frozen sectionA tap with no flow, or just a trickle, points to a freeze somewhere between there and the stopcock. Check exposed pipework first: lofts, garages, under suspended floors and pipes against outside walls freeze quickest. Use a torch to look for a frost patch, a bulge, or split lagging.

1 each · Torch

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TP-04Open the affected tap fullyOpen the tap that the frozen pipe feeds and leave it open. This lets meltwater flow away as you work instead of building up pressure inside the pipe, which is what causes splits.

TP-05Warm the pipe gently, starting nearest the tapWrap a hot water bottle in a towel and hold it against the pipe, or use a hairdryer on a low heat setting held a short distance away. Always start at the tap end and work back towards the blockage, never the other way, so meltwater has somewhere to go. Never use a blowtorch, heat gun or any open flame on a pipe — it can scorch joists, melt solder joints, or set fire to insulation.

1 each · Hot water bottle

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TP-06Watch for leaks as it thawsFreezing sometimes splits a pipe without you knowing until it thaws. Keep a bucket underneath the section you're warming and listen for hissing or dripping. If you see a leak, stop straight away and shut the stopcock fully — don't try to carry on thawing.

1 each · Bucket

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TP-07Check the water is running properly againOnce water flows steadily and evenly from the tap, turn the stopcock back on fully. Check other taps in the house run normally too, and look along the thawed pipe and its joints for any drips. Run the cold tap for a minute to flush the system through.

TP-08Insulate the pipe so it doesn't freeze againFit foam pipe lagging over the section that froze, matching the lagging's internal diameter to your pipe size. Push the two halves together over the pipe and tape the joins closed. Pay particular attention to pipes in lofts, garages and against outside walls.

2 each · Foam pipe insulation, 1m length

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1 roll · Insulation tape

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TP-09Tidy up and keep an eye on itMop up any water and dry the area around the pipe. Keep checking the pipe and its joints over the next 24 hours, since a hairline split can leak slowly rather than straight away. If temperatures are due to drop again, leave a trickle running from the tap overnight or open cupboard doors to let warm air reach the pipe.

2 each · Old towels or cloths

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