Condensate pipe dripping heavily or boiler stops in freezing weather

Safety: Condensate is mildly acidic. Wear gloves and eye protection when handling.

• Check external pipe: In cold weather, look for ice on the white/grey plastic condensate pipe outside. If frozen, the boiler may lock out with ignition or flue-related codes.
• Thaw pipe: Pour warm (not boiling) water along the length of the pipe to melt ice. Do not use open flames.
• Reset boiler: Once thawed, reset the boiler and check operation.
• Prevent recurrence: Insulate the external condensate pipe and, if possible, increase its diameter and reduce length as per Vaillant and local guidance.
• Engineer cleaning: If the internal condensate trap is blocked, a technician should remove and clean it.