Frozen condensate pipes

If you have a modern high efficiency boiler, as it heats the home it creates water vapour. The condensate pipe helps to drain this liquid away from the boiler, allowing it to function at its optimal level. Depending on your boiler installation type, the condensate pipe might be situated internally, or as an external feature. If it is the latter then it stands a far higher chance of freezing when the weather turns cold, with the HHIC stating that this is particularly likely ‘when there is a high wind chill factor’. If this happens, it is important to fix the issue, otherwise your boiler might not perform as expected.


Like most things, the best way to protect your condensate pipe from freezing is to ensure that it has been fitted properly and insulated. However, the HHIC has found that ‘a significant proportion of installations are not installed to current standards and manufacturer’s instructions’, which means that many Britons are currently at risk.

If this is the case, then it is advisable to retrofit a high quality, closed cell foam pipe insulation around the pipe. Unfortunately, insulation alone is often not enough to deal with very extreme temperatures of below freezing - as witnessed during the 2018 ‘Beast from the East’.

An alternative option is our innovative Alpha E-Tec Trace Heating Kit. The 3m electric trace wire eliminates the risk of frozen condensate pipes and prevents any subsequent damage to the boiler. This simple solution is controlled by the boiler in conjunction with an outside weather probe, which also makes the installation Boiler Plus compliant (where required in England).

Even with precautions in place, it is always important to know how to effectively defrost the condensate pipe if needed.


Fortunately, defrosting a condensate pipe is a relatively straightforward process. In fact, by following this handy guide, you should be able to tackle the issue yourself:

    Some modern boilers will inform you when the condensate pipe has frozen by displaying a warning message on the system’s display. If your boiler does not have a display, then you can look and see if the condensate pipe is frozen. Check to see if the pipe has any visible signs of frost, or if it is making any gargling noises, both of which are indications that it is either partially or fully frozen.
    Once you have confirmed that the pipe is frozen, it is important to locate the exact point where the blockage has occurred. Normally, pipes will freeze at their most exposed points, so it is worthwhile checking the open end or any bends first before examining other areas. Simply run your hand down the pipe until you find an area that feels colder than the rest of the pipe. Normally, this will be the site of the frozen blockage.
    This is the most important step in the process and also the stage where you need to take the most care. One of the most effective ways to thaw the frozen blockage is with warm water, however it is crucial not to use boiling water, which can crack the pipe. Carefully remove any pipe lagging and pour warm water down the side of the pipe, repeating the process until you start to notice it thawing.
    Once you are happy that your condensate pipe has been defrosted and the frozen blockage has gone, you can restart your boiler. As always, it is important to follow the manufacturer’s guidance on how to do this safely. Once the system has restarted it should now function as normal. Don’t forget to replace any lagging removed from the condensate pipe during the thawing process.


Having followed these steps, your boiler should now be working as normal. However, if you have followed the step-by-step guide above and the issue does not seem to have been resolved then you should try running through the steps a second time, as it can sometimes take a while for a condensate pipe to defrost fully. If you have tried to thaw your condensate pipe several times, but your boiler is still underperforming then this might be indicative of a bigger problem. In these instances, it is always best to call a Gas Safe Registered engineer to examine the issue.


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