Water softener leaks from the drain hose during normal service (not regenerating)

Safety first: Disconnect power, close inlet and outlet valves, and open a tap to relieve pressure before working on the valve head.

• Confirm leak condition: Ensure the leak occurs during service mode and not only during regeneration (some flow during regen is normal).
• Inspect drain line: Remove the drain hose from the valve head and check for continuous flow when the unit is in service. Any flow indicates internal leakage.
• Disassemble valve head: Remove the valve head and inspect the main piston and drain seals for wear, cuts, or deformation.
• Clean and replace seals: Clean internal passages and replace worn seals using a Viessmann valve seal and piston kit.
• Reassemble and test: Reinstall the valve head, reconnect the drain, and verify that no water flows to drain in service mode.