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Common winter boiler enquiries

Thawing and preventing frozen condensate pipes

During periods of very cold weather, we occasionally receive enquiries from customers whose boilers’ do not appear to be working.

Sometimes this is down to the condensate discharge pipe freezing which can prevent the boiler from operating. This is an industry-wide situation and is not unique to Worcester boilers.

Video on how to safely thaw a frozen condensate pipe.


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 trap/discharge pipe has frozen?


Step 1 It’s possible that your boiler’s condense trap/discharge pipe has frozen if all 3 of these statements are correct:

  • The outside temperature is or has been below freezing
  • Your boiler is displaying either an EA fault code, a D5 code or is displaying a flashing blue light (for 26CDi boilers you may see a flashing red light instead)
  • Your boiler is a Greenstar gas boiler, or a 26 CDi

Step 2 If all 3 statements are true, you should now try to reset your boiler. This can be done by holding in the ‘reset’ button (this can be found on the boiler control panel) for 10 seconds. Once you have released the button you should wait 2 to 3 minutes to see if the boiler re-fires.

Step 3 If the boiler does not re-fire and it is emitting a gurgling sound, then it is almost certain that your condense is frozen. If you cannot hear a gurgling noise you should still proceed to check your condense pipe.

Step 4 The condensate pipe is 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 and the 3 criteria (in step 1 above) apply then it is likely that it is frozen and needs to be thawed.

How can the condensate pipe be thawed?

You should contact your boiler installer in order to thaw the condensate pipe and find a permanent solution to the freezing condensate problem.

(If you would like to contact a Worcester Accredited Installer near you please use our Find an Installer search)

If you are unable to contact your installer then you could do the following, however, 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.
  • If you are uncertain of what to do or require particular assistance then you could invite a neighbour/friend or family member to assist you. The person assisting you can, if required, contact our Technical Support Team (0330 123 3366) for assistance.
  • Once thawed, you should still contact your installer in order to implement a permanent solution to the condense freezing.

What should I do if I have a different problem, or if following this advice has not worked?

Please contact our Customer Service team on 0330 123 9339*.

Prevent frozen condensate

Image of Condensure1We have developed our new CondenseSure device to help prevent external condensate pipes freezing, even in the harshest winter weather conditions found in the UK and Ireland.

CondenseSure requires no electricity and is compatible with any gas condensing boiler on the market, either at the time of installation or as a retrofit.

The device is designed to collect condensate, keep it warm and discharge it via pipework in a way that has an anti-freezing effect.

Download the CondenseSure brochure


More questions and answers about freezing condensate pipes

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.

What is a condensate trap/discharge pipe?

The Greenstar range of gas and oil-fired boilers dispose of their condensate by means of a syphonic trap, which discharges a given quantity of condensate fluid at a time to the properties drainage system/pipe work.

The syphonic trap is important because if the condense fluid were allowed to drip continuously to the drain at the rate it was being produced, then there would be an increased risk of any externally run condense discharge pipe freezing.

Why might the condense trap/discharge pipe freeze?

Despite the syphonic trap flushing method, when the outside temperature is below freezing for a prolonged period of time, externally run discharge pipes, or discharge pipes that are run through a cold area of your property (e.g. garage or loft), can freeze, particularly if they are not insulated (lagged), or sized appropriately.

What will happen if my condense trap/discharge pipe has frozen?

The condensate will be unable to drain away and this would lead to the ‘backing up’ of the condense, which will cause the boiler to fail and go to ‘lockout’.

If this happens to a gas boiler, then the boiler will likely to be showing an EA fault code, or alternatively it will show a flashing blue light and the boiler may be emitting a gurgling sound.

What does the flashing EA code/blue slow flashing light mean?

There are various reasons your boiler may display these codes or lights. They do not necessarily mean your boiler is faulty. A frozen condensate trap or discharge pipe could cause these codes - refer to the steps above to check.

Will the advice on this page work if my boiler isn’t a Worcester?

For industry-wide guidance please click on the link to see advice from the Heating and Hot Water Industry Council (HHIC):
HHIC frozen condensate advice for householders


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