Commercial boiler breakdown on the coldest day of the year? Put the kettle on.

A commercial boiler breakdown can be costly in call out charges and a disruption in productivity at the office or workplace. But before you call out the engineer, check to see if the problem is a frozen condensate pipe – it’s one of the most common causes of a boiler shut-down in winter and one you can fix yourself – all for the price of boiling the kettle.

Here you can learn what it is, where to find it, how to fix quickly without waiting for a heating engineer and how to prevent it happening again.

What is a condensate pipe and where would you find it?

Often a grey or white pipe usually located externally, it drains away excess water from the boiler created during the heating process.

What causes it to freeze?

Extreme weather conditions - below freezing - usually over a prolonged period. The blockage will in turn cause the boiler to shut down.

How to find it and fix it

Firstly, confirm it’s a frozen pipe. Usual signs are a shut-down of a regular serviced, well running, boiler following prolonged severe freezing weather.

You can also check the ‘fault code’ on your boilers’ digital control panel for flashing lights/error codes. Other signs include a ‘gargling’ or ‘slurping’ noise when you switch the boiler on.


  1. Find the blockage – likely an open end or bend
  2. Thaw the pipe – use warm (not boiling) water, a hot water bottle, heat pad or even warm blankets
  3. Re-start the boiler (checking the manufactures guidance).
Note: Do not attempt to thaw a pipe if you cannot comfortably reach it. Never attempt to dismantle your boiler – this should always be done by a gas safe engineer. Always check the manufactures warranty.

How to prevent in happening again in future

Adding condensate pipe insulation to the pipe will stop it from freezing over. Ensure its suitable for external use such Armaflex External Pipe Insulation. Also think about:
  • During severe freezing weather periods set your boiler to run on ‘continuous’ (24 hours) and increase the thermostat to maximum
  • Arrange for gas safe registered engineers to check your condensate pipe and advise of any upgrades or changes that may reduce freezing in future. This could include relocating the pipe, upgrading the pipe or adding insulation.

Always ensure that any work carried out is to current standards.  

Disclaimer: Please only attempt to fix the issue if you feel competent and it is safe to do so. Never attempt to dismantle a boiler – always call a Gas Safe engineer.

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