Water remains hard at taps even though the softener appears to run normally (no error code)

Safety first: No immediate disassembly is required. Keep the unit powered and in service mode.

• Test hardness: Use a hardness test kit on both raw and softened water. If both are similar, the softener is not working effectively.
• Check bypass: Verify that the Viessmann bypass valve is fully in the service position and not partially bypassing the softener.
• Verify settings: Confirm that the raw water hardness and capacity settings in the controller match the actual water analysis.
• Inspect salt and brine: Ensure the brine tank has adequate salt and that the water level is correct. Run a manual regeneration and retest hardness after completion.
• Resin condition: If hardness remains high, plan to replace or chemically clean the Viessmann ion-exchange resin, especially if the system is older or exposed to high iron.