Frozen pipes and central heating problems

During the cold winter months it is not uncommon for boilers and central heating systems to be put under additional strain that results in them performing less efficiently, or not at all.

This can sometimes be the result of the condensate discharge pipe freezing and preventing the boiler from operating. The following information will assist you in identifying whether you have such an issue with your boiler and what should be done about it.

How can I tell if the boiler's condense pipe has frozen?

It is likely that your boiler has stopped working due to a frozen discharge pipe/condense trap if:

  • your boiler is a Greenstar gas boiler, or a 26 CDi
  • the outside temperature is, or has been, below freezing
  • it is displaying either an EA fault code or a flashing blue light (for 26CDi boilers you may see a flashing red light instead)

If these statements apply to you, you should try to reset your boiler. This can be done by holding in the 'reset' button which is usually found on the boiler control panel. Once you have released the button you should wait 2 to 3 minutes to see if the boiler refires.

If the boiler does not refire and is emitting a gurgling sound, then it is almost certain that your condense trap is frozen. If you cannot hear a gurgling noise you should still proceed to check your condense pipe.

What is a condensate pipe?

The condensate pipe will be a plastic pipe (black, white or grey), coming from the bottom of your boiler. If this pipe is less than 32mm in diameter and runs outside of the property or through a non-heated area then it should be fully insulated with waterproof lagging. If it is not fully lagged, it is highly likely that it is frozen and needs to be thawed.

How can the condensate pipe be thawed?

You should exercise extreme caution at all times when attempting to identify and thaw a condensate pipe.

  • You should only attempt to thaw a condense pipe that is at ground level and which is easily accessible to you. Under no circumstances should you attempt to thaw a condense pipe which is at height, without the assistance of a professionally trained engineer.
  • A hot water bottle or heat wrap (like the ones that can be used to ease muscle discomfort) would be a suitable and safe way of thawing the condense pipe. Hold the hot water bottle or warmed heat wrap around the condensate pipe to thaw it.
  • Once thawed, the boiler must be reset. This can be done by holding the reset button in for 10 seconds and then waiting 2 to 3 minutes for the boiler to refire.

What is 'condensate'?

Condensate is moisture gathered from the boiler's flue and allowed to run back through the boiler to a collection point. Condensate is a feature of condensing boilers. For further information please visit

What to do if you discover a problem

  • If you haven't any water, check with neighbours. If they have no interruption to their supplies, your pipes may be frozen
  • Check pipes for signs of a split – a burst will not occur until the water has thawed
  • Turn off the supply using the stopcock
  • Drain the system by flushing the toilet and opening cold taps over sinks and baths
  • Turn off the central heating and any other water heating appliances
  • If you don't find any damage, turn on all the taps and thaw the frozen pipe using a warm towel or hot water bottle
  • When the pipes have thawed and you are sure no damage or leak has occurred, turn off the taps and slowly switch the supply back using the stopcock
  • Check the pipes again now that they are under pressure and check again for signs of damage or a leak before switching on water heating appliances
  • If you discover a leak or burst pipe, call a reputable plumber immediately

For more detailed information please visit the Yorkshire Water website.