E09
De Dietrich
Safety Valve / Overpressure Fault
Boiler shows E09, safety valve discharge detected (if sensor fitted) or frequent pressure drops
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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
Stuck or leaking 3 bar safety valve on De Dietrich hydraulic group, Overfilled system pressure, Failed expansion vessel, Limescale or debris on valve seat
How to Fix / Troubleshooting
Safety: Discharged water may be hot. Use caution around the discharge pipe.
Steps:
- Check system pressure: If cold pressure is above the recommended level (e.g., >2 bar), reduce it by bleeding radiators or using a drain point.
- Inspect discharge pipe: Look for signs of regular dripping from the safety valve outlet. Continuous dripping indicates a faulty valve or expansion issue.
- Do not cap the discharge: Never block or cap the safety valve outlet.
Professional help: A technician should replace the safety valve if it does not reseat properly and address any expansion vessel problems.
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Repair Difficulty
Medium
3/5
Required Part
3 Bar Safety Valve
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