The boiler's condensate pipe repeatedly freezes in cold weather.

Safety: Do not pour boiling water on plastic pipes. Turn off the boiler if condensate backs up and causes gurgling or leaks.

Steps:

• Thaw the external condensate pipe gently with warm water or a hot water bottle.
• Insulate the external section with weatherproof lagging.
• Where possible, reroute the pipe internally or increase its diameter to at least 32 mm as per best practice.
• Ensure the pipe has a continuous fall to the drain to prevent standing water.