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It’s that time of year again! Dropping temperatures and heavy snowfalls cause havoc on the roads.  It’s the time of year when heating engineers get huge numbers of calls because high efficiency boilers stop working when their condensate pipes have frozen up.  When the condensate liquid from the boiler freezes in the pipe and can’t escape, the boiler shuts down to protect itself from damage.  In the majority of cases, this happens because the pipe that carries the condensate to a suitable drain is located outside the building, or in an area without heating such as a loft or garage.

British Standards, Building Regulations and boiler manufacturers’ installation instructions currently allow condensate drainage pipes to be located either internally or externally, or a combination of these.  They give guidance on how to install the condensate drainage pipes to reduce the possibility of freezing.  However this guidance may not be sufficient to prevent freezing during the prolonged very low temperatures recently experienced in the UK.   

How can you tell if your boiler condensate pipe is frozen?

A frozen condensate discharge pipe may be indicated in a number of ways depending on the specific model of boiler you have:

• Error codes either E133 or E4 on the alphanumeric boiler display (for Baxi boilers)
• No flame symbol displayed
• Gurgling water noises coming from the boiler. 
• Please note your boiler may have some minor differences to those shown below but the error code or flame failure indication will be the same.

What should I do next?

Baxi’s service division heateam has created this useful video to help you thaw the condensate pipe and reset your boiler. 

1. Locate the blockage
It is likely that the condensate discharge pipe is frozen at the most exposed point external to the building or where there is some obstruction to flow. This could be the open end of the pipe, at a bend or elbow, or there is a dip in the pipe in which condensate can collect. The location of the blockage should be identified as closely as possible before taking further action.

2. Thaw the frozen pipe
The first method of thawing the frozen condensate discharge pipe is to pour hot water (NOT BOILING) over the outside of the frozen section of the pipe using a suitable container, such as a watering can.

This could take around 30 minutes but the boiler will not ignite until the pipe is fully thawed. If your boiler is out of use as a result of the frozen condensate discharge pipe you could heat the water using a kettle or microwave.

You could also use a hot water bottle or heat wrap, the sort that is usually used to ease muscular discomfort. These heat wraps are available at your local pharmacist. If you have chosen to use a hot water bottle hold it against the frozen section until the condensate discharge pipe is fully thawed.  This process may also take some time but again the boiler will not ignite until the blockage is fully thawed.

Please note you should not attempt to thaw a condensate discharge pipe, if it cannot be easily accessed from ground level. Also do not attempt to disconnect the condensate discharge pipe at any time during this process. Only attempt to thaw a frozen condensate discharge pipe if you feel competent to do so.

3. Reset boiler
Once the condensate discharge pipe has fully thawed, the boiler will need to be reset using the reset switch. Once reset the boiler should fire up and run as normal.

4. What should I do if I cannot reset my boiler?
If you are unable to reset your boiler, call your local Gas Safe registered engineer or call heateam, Baxi’s service division, on 0844 335 2266.

How can I prevent my condensate pipe from freezing in the future?

Watch this video from heateam for some suggestions on ways to prevent your condensate pipe from freezing again.

You will need to speak with a Gas Safe Registered installer who may recommend some remedial action that can be taken to prevent recurrences of the condensate discharge pipe freezing. Some options may include:

• Identify alternative route inside your property (or use a condensate pump)
• Increase external pipe diameter externally to 32mm
• Ensure all exposed condensate discharge pipework is insulated with waterproof insulation
• Fit trace heating
• Ensure condensate discharge pipes are connected into soil pipes only (110mm)

For more information:

heateam website – frozen condensate pipes

HHIC website – Help for frozen condensate pipes

Gas Safe Register