Common winter boiler problems

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Winter boiler problems

During periods of very cold weather, there is an increase in instances where the condensate drainage pipe from condensing (high efficiency) boilers freezes. A blockage due to freezing can cause a visible leak underneath the boiler or even result in it shutting down.

This note gives brief guidance for householders on what to do in this situation.

Locate the blockage

It is likely that the 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 where 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.

Thaw the frozen pipe

The pipe can be thawed by applying a hot water bottle, a microwaveable heating pack (the sort used for muscular aches and pains) or cloths soaked in warm water to the exterior of the pipe, close to the point of blockage. Warm water can also be poured onto the pipe from a watering can or similar container. Do not use boiling water.

Note: You should not attempt to thaw a condensate drain pipe which cannot easily be reached from ground level. Be aware that any water used can quickly freeze if it falls on pathways - causing a possible slip hazard.

Re-set / Re-start the boiler

Once the blockage has cleared consult the boiler operating instruction, or check our Website for guidance on any action needed to re-start the boiler. If this does not succeed you should call in a competent engineer to assess the situation and take further action if required.

Temporary remedial actions

If the pipe is successfully thawed and the boiler can be re-started then the following temporary remedial actions may help prevent re-freezing if the severe weather continues.

If the external pipe is not lagged as recommended then you should try to insulate the pipe with suitable weather-proof lagging, in order to prevent re-freezing.
During the cold spell it may help to run the heating system with the boiler thermostat (NB not the room thermostat) set to maximum. Turn back to the normal setting once the cold spell is over.
It may also help to temporarily set the central heating timer/room thermostat controls to “continuous” (24hr) mode, setting the room thermostat overnight to around 15^oC. Again, return to normal settings once the cold spell is over.