Frozen Pipes: How to Thaw One Without Bursting It

Open the tap, then thaw from the tap end

Open the tap that the frozen pipe feeds, both hot and cold. Leave it open the entire time.

Why that is not optional. Melting ice makes water, and too much heat in one spot makes steam. If both ends of the plug are sealed, that pressure has one job, which is to find the weakest point in the pipe. An open tap gives it somewhere to go.

It also tells you when you have won. A trickle turning into a flow is the signal to keep going, and there is nothing else that tells you.

Now heat the pipe starting nearest the tap and move slowly back along it towards the frozen part. Melt water then runs out in front of you instead of being trapped behind a second plug of ice.

What to heat it with. A hair dryer on the move, a heating pad wrapped round it, towels soaked in hot water, or a space heater pointed at the area from a safe distance. Slow and wide beats hot and narrow.

How long. It depends on how cold the space is. The Red Cross says to keep the heat on until full water pressure is back. If you make no progress, it is likely to be inside a wall or underground, and the Red Cross says to call a licensed plumber when you cannot reach or thaw the frozen part.

Let the taps tell you where to look

Nothing anywhere in the house. The freeze is at or before the point the supply comes in, often in the crawl space, the meter pit or under the front of the house.

One tap only. That branch, and usually the last few feet of it. A kitchen sink on an outside wall is a common spot.

Hot works, cold does not, or the other way round. Then it is one of the two runs, which narrows it to a few feet rather than the whole house.

Follow the cold. Run a hand along the accessible pipe. The frozen section is noticeably colder and often has frost or condensation on it.

The six usual places. An outside wall, the crawl space, an unheated garage, the attic, a cupboard against an outside wall, and anywhere a pipe passes a vent, an air brick or a gap round a cable.

If it is inside a wall. Open the cupboard doors, put a space heater in the room aimed at that wall, turn the house heating up and be patient. Cutting a wall open is the last resort and not the first one.

The first minutes that decide the size of the bill

Water off at the main. Then open every tap in the house to drain what is left in the pipes and take the pressure off.

Power off if water is anywhere near anything electrical. At the panel, not at the appliance.

Switch off the water heater. If the supply is off and the tank empties, elements and burners are heating nothing: the right order to shut one down.

Then photograph everything before you mop, because that is what an insurer asks for.

A split is often small. A pipe that has burst usually has a short slit where the ice pushed hardest, and that is a repair rather than a replacement.

What actually works, in the order it works

Seal the draught first, insulate second. This is the part almost nobody gets right. Insulation slows heat leaving the pipe, it does not add any. A pipe with cold outside air blowing onto it through a gap will freeze through insulation. Find the gap: where the cold air actually gets in.

Let a tap drip when it is really cold. A thin steady trickle on the run that has frozen before. Moving water is much harder to freeze, and it is pennies of water against a burst pipe.

Open the cupboard doors under sinks on outside walls, so the room’s warm air reaches the pipes.

Never drop the heat below about 55 while you are away. Turning it off entirely to save money over a week away is how people come home to a flooded house.

Disconnect the garden hoses in autumn and shut off the outside taps from inside if you have that valve. A hose left on holds water right at the wall.

Heat tape on the pipe that keeps doing it. Buy the kind with a thermostat, fit it exactly as the instructions say, and never wrap it over itself.