Thaw frozen pipes without cracking the run

The call always comes the same way: no water at the kitchen tap this morning, or a strange bulging quiet in the pipes, and outside it is the coldest night of the year so far. A frozen pipe is recoverable; most thaw back without a scratch. The danger is in the thawing, because a pipe that freezes solid can split along its length while frozen, and the crack only announces itself when the ice lets go and the water comes back. The order that matters is: control the water, open an outlet, apply gentle heat, and keep watching.

Which pipes freeze first

Water freezes where the cold finds the pipe: lofts (cold air, thin pipes, often the shower feed), garages and outbuildings, under kitchen floorboards against an outside wall, the stretch behind a bath panel on a north wall, and any run in a cavity. A classic example in many homes is the loft run to a shower, or an outside tap fitted without an isolating valve.

The symptom is absence: a tap that runs dry while its neighbours still work. That pattern, one outlet dead, the rest alive, is the fingerprint of a local freeze, and it names the run that is frozen without opening anything.

The first ten minutes, in order

1. Turn off the water at the stop tap. If the pipe has already split, this is the difference between a mop and a claim. If you cannot find it, find and label it before the next cold night.
2. Open the tap the frozen pipe feeds. Thawed water needs somewhere to go, and an open outlet is also your sensor: the moment flow returns, you will see it, and if the pipe has split, the water goes where you can see it, not into the ceiling.
3. Apply gentle heat to the pipe. A hot water bottle or heat pad wrapped against the run. A hair dryer on its lowest setting, moved constantly. Towels soaked in warm (not boiling) water laid along the metal. That is the whole toolkit.
4. Work from the tap end towards the frozen section, so thawed water can escape as it goes instead of building pressure behind an ice plug.

What never touches a frozen pipe

A blowtorch or any naked flame, first and always: it thaws a small spot, scorches everything near it, and has started more house fires than plumbers care to count. Boiling water poured directly on is nearly as bad: thermal shock on cold copper, scalds on wrists, and no control over where the heat lands. And do not leave an electric heater pointed at pipework overnight and go to bed; unattended heat is how a thaw becomes a fire report.

If the pipe has already split

Water appearing as the thaw progresses, or a bulge, a crack, or frost on the outside of a joint: stop heating, keep the stop tap closed, open the low taps to drain what it can, catch what drips, and move what water-sensitive things live below the run. Then call a qualified plumber. A split pipe on an accessible run can be repaired fairly quickly, which is why catching it before full thaw matters: the repair is calmer than the rescue.

Next summer, the pipe that froze

Freeze events are a maintenance calendar item: lag the loft run (pipe insulation, properly sized, joints included), fit an isolating valve and drain-off on outside taps, check the loft hatch lets some warmth reach the cold tank, and know which runs sit in cavities. On very cold nights, leaving the loft hatch ajar and the furthest tap at a pencil-thin trickle helps keep water moving. Moving water freezes last, and this is one of the cheapest prevention measures. Check your water supplier's cold-weather guidance for any specifics.

What this sheet does not cover

Frozen condensate pipes on boilers, a different job with its own notes in the boiler breakdown sheet, are not covered here, nor is trace-heating tape for genuinely exposed runs, nor repairs to communal risers in flats, which belong to the managing agent. If the mains itself is frozen at the boundary, that is the water company's side of the stop tap; contact your water supplier directly.