Viessmann
Condensate / Flue Drainage Fault
Condensate dripping from flue joints or outside wall
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Incorrect flue slope, failed flue joint seals, blocked condensate trap, damaged condensate hose
How to Fix / Troubleshooting
Safety: Condensate is mildly acidic; wear gloves and eye protection when handling.
- Inspect flue slope: The Viessmann concentric flue should slope back towards the boiler to allow condensate to drain internally.
- Check joints: Look for staining or drips at flue joints; do not dismantle the flue yourself.
- Condensate trap: Clean the condensate trap and ensure the outlet pipe to the drain is clear and properly supported.
- Technician repair: A qualified installer should refit or replace flue sections and seals to restore condensate-tight integrity.
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Repair Difficulty
Hard
4/5
Required Part
Condensate Trap / Flue Seals
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