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 video demonstrates how to safely unfreeze 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:

• 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 some boilers you may see a flashing red light instead)

Step 2 You should try to reset your boiler following the manufacturers instructions.

Step 3 If the boiler does not reset 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? 
If you feel comfortable 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.
• 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.
• If you are unsure or have any doubts then contact West North West homes Leeds on 0800 915 1113 (free from a landline).

What should I do if I have a different problem, or if following this advice has not worked? 
Please contact WNWhL Customer Services on 0800 915 1113 (free from a landline).

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? 
Some 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.

Further information is available in the leaflet available from the link to the right.