Viessmann Valve Head / O-Ring Leakage

Water softener leaks from around the valve head or top cover

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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

Damaged valve head O-ring, Cracked valve body, Loose valve head screws, Debris on sealing surfaces

How to Fix / Troubleshooting

Safety first: Disconnect power, close inlet and outlet valves, and open a nearby tap to relieve pressure before disassembling.

  • Identify leak source: Dry the area and observe where water emerges (around the valve head, fittings, or cover).
  • Tighten fasteners: Gently tighten the valve head screws evenly. Do not overtighten, as this can crack the housing.
  • Inspect O-rings: Remove the valve head according to the service manual. Check the main O-ring and any port seals for cuts, flattening, or debris.
  • Clean and replace: Clean sealing surfaces and replace damaged O-rings with genuine Viessmann valve head seal kit.
  • Reassemble and test: Reinstall the valve head, slowly pressurize the system, and check for leaks.
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Repair Difficulty

Hard 4/5

Required Part

Viessmann Valve Head Seal Kit
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