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

Safety: No electrical work is required for basic checks. Wear gloves when handling salt and resin.

Steps:

• Test hardness: Use a hardness test kit on both raw and softened water. If both are similar, the softener is not exchanging ions effectively.
• Check bypass position: Confirm that the Vaillant bypass valve is in the correct "service" position. A partially open bypass will dilute softened water with hard water.
• Inspect salt and brine: Open the brine tank and check for a salt bridge (a hard crust above a void). Push a plastic rod down through the salt; if it suddenly drops, break up the bridge and remove loose chunks.
• Run manual regeneration: After correcting salt issues, initiate a manual regeneration and retest hardness 1–2 hours after completion.
• Consider resin condition: If the unit is older or has been exposed to iron or chlorine, the resin may be fouled or exhausted. In that case, the resin cartridge or cylinder should be replaced.