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Cambridge City Council

Defrost a frozen pipe

If your pipes freeze in cold weather:

  • turn off the water supply at the stop tap
  • turn off the central heating or put out the fire if you have a back boiler
  • drain the water system by turning on the taps until they run dry
  • find out where the pipe is frozen
  • if it is frozen in the loft, open the hatch to let the warmer air in
  • thaw the pipe with a fan heater, hairdryer or hot-water bottle

If your heating is affected and you are a council tenant, we might be able to provide some portable heaters. Contact us to check.

Frozen pipes on gas boilers

If your gas boiler stops working in cold weather, it is likely to be caused by a frozen condensate pipe.

The condensate pipe is usually a white plastic pipe that comes out below the boiler and runs to the outside of the property.

If you have a Glow-worm boiler and it displays error code F1, F4, F28, or F29, there’s an issue with your condensate pipe. This error appears when the pipe is frozen, which can happen in cold weather.

Condensate pipes usually freeze at the most exposed point, outside your property.

To thaw the pipe and fix the problem, pour lukewarm water over it. Do not use boiling water or the pipe might crack. You might need to do this several times. Take care when doing this – if the water freezes on the ground it could cause a slip hazard.

To check whether the pipe has thawed, press the reset button on the front of the boiler, or turn it back on if you had turned it off. If it starts, the pipe has thawed. If it does not, try pouring more warm water on the pipe.

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