Boiler stops and shows error 25; condensate may be visible around the unit or in the base tray.

Safety first: Turn off power to the boiler. Condensate is mildly acidic; wear gloves and eye protection when handling.

• Inspect condensate trap: Locate the condensate trap at the base of the boiler. Place a container underneath, remove the trap, and empty it. Rinse thoroughly with clean water to remove sludge.
• Check condensate pipe routing: Ensure the pipe slopes continuously downward to the drain with no upward loops or sags that can hold water.
• Clear external termination: If the condensate discharges outside, check for ice, dirt, or blockages at the outlet. In freezing weather, thaw the pipe gently with warm (not boiling) water or a warm cloth.
• Reassemble and test: Refit the trap securely, restore power, and reset the boiler. Observe for leaks and confirm that condensate flows freely during operation.
• Persistent issues: If error 25 returns, have a technician inspect the condensate level sensor and internal drain passages.