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HHIC guidance on frozen condensate pipes

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Due to the unusually cold weather we’ve been having, there has been a significant increase in the number of householders with condensing boilers, experiencing frozen condensate drainage pipes; causing temporary boiler shut-down. Problems occur when the condensate drainage pipe is located externally, for some or all of its length.

Unfortunately, climate change means that in the UK very cold winters are likely to become the norm. The Heating and Hot Water Industry Council (HHIC), which represents all major UK manufacturers and merchants throughout the UK, has consequently brought installers attention to the guidance provided with condensing boilers. This information, alongside individual manufacturer’s documents, clarifies the recommendations for the location/routing of condensate drainage pipe work.

A summary of the HHIC document is as follows:

Wherever possible, the condensate drainage pipe should be terminated at a suitable internal foul water discharge point – such as a soil and vent stack, kitchen or bathroom waste pipe, washing machine waste pipe, etc – the condensate must drain away from the boiler under gravity.

Where internal termination under gravity flow is not possible, the installer must ensure that the customer is made aware of the risks of external pipes freezing. If this is the case, the following options should be given:

• If very long runs of drainage pipe are required, or where the only internal discharge point is above the appliance location, one option is to remove the condensate using a proprietary condensate pump. This will allow the condensate drain to be terminated internally at a suitable foul water discharge point.

• Where an external pipe run is the only practicable option, refer to British Standard BS 6978:2009 and the boiler manufacturer’s instructions. The external run should be short and as near vertical as possible, terminating at a suitable foul water discharge point or purpose-designed soak away. The customer should be made aware that these measures alone may not completely prevent freezing.

• The use of a proprietary trace heating kit should be considered. This will provide heat to the external pipe run, but only when the boiler is running and the outside temperature falls below a prescribed limit.

When installing a boiler, gas engineers must always refer to all the documentation and guidance provided.

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