Frozen Condensate Pipe — How to Thaw and Prevent It

Frozen Condensate Pipe Fix

In cold weather, the condensate pipe (which carries acidic condensation from the boiler outside) can freeze. When it does, the boiler locks out and displays a fault code.

How to Identify a Frozen Condensate Pipe

• Boiler has locked out in cold weather
• Fault code related to flue or ignition (varies by brand)
• Gurgling or glugging noise from the boiler before lockout
• Condensate pipe (usually the white plastic pipe exiting the house) is visibly frozen

How to Thaw It

1. Locate the condensate pipe — usually a plastic pipe (25–32mm) that exits through the wall
2. Pour warm (not boiling) water over the frozen section until thawed
3. Alternatively, use a hot water bottle held against the pipe
4. Once thawed, reset the boiler

Prevention for Next Winter

Lag the external section of the condensate pipe with pipe insulation. This is a simple DIY job and prevents recurrence. We can do this as part of an annual service.