Condensate pipe outside frequently freezes in cold weather, causing boiler shutdowns

Safety: Do not use boiling water or open flame on plastic pipes.

• Thaw pipe: Pour warm (not boiling) water over the external condensate pipe and trap area, or wrap with warm towels until thawed.
• Reset boiler: Once thawed, reset the boiler and confirm normal operation.
• Insulate pipe: Add weatherproof insulation to the external condensate pipe to reduce freezing risk.
• Professional rerouting: A technician can increase pipe diameter, reduce external length, or reroute internally according to Viessmann guidelines.