Viessmann
System water leak / condensate or heating circuit leak
Water leaking from the bottom of the Viessmann furnace or from attached pipework
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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
Leaking pressure relief valve, Corroded heat exchanger, Loose union connections under boiler, Cracked condensate trap or hose
How to Fix / Troubleshooting
Safety: Turn off power if water is leaking onto electrical components. Hot water can cause burns.
- Identify leak source: Remove the front cover and use a flashlight to trace the leak. Check the pressure relief valve discharge, pump unions, and heat exchanger connections.
- Check pressure relief valve: If water is dripping from the relief valve discharge pipe, system pressure may be too high or the valve may be fouled. Reduce pressure to 1.5 bar and see if dripping stops.
- Tighten unions: Gently tighten any slightly loose compression or union fittings under the boiler. Do not overtighten.
- Condensate leaks: Inspect the condensate trap and hoses for cracks or dislodged connections. Re-seat or replace as needed.
- Serious leaks: If the heat exchanger or internal manifolds are leaking, shut down the boiler and call a Viessmann technician for component replacement.
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Repair Difficulty
Hard
4/5
Required Part
Pressure Relief Valve
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