Error Code	Symptom	Fault Type	Guide
F01	Display shows F01 and the softener does not start a regeneration cycle	Inlet Water Supply Fault	View Details
F02	F02 displayed and unit does not draw brine during regeneration	Brine Suction / Injector Fault	View Details
F03	F03 error and softener stuck in regeneration or cannot complete cycle	Motor / Valve Positioning Fault	View Details
F04	F04 displayed and no water flow is registered even when taps are open	Flow Meter / Turbine Signal Fault	View Details
F05	F05 error and the unit reports low salt even when the brine tank is full	Salt Level Sensor Fault	View Details
F06	F06 displayed and the softener does not regenerate at the programmed time	Real-Time Clock / Programming Fault	View Details
F07	F07 error and the display shows abnormal temperature or freezes during regeneration	Control Board Overtemperature / Sensor Fault	View Details
F08	F08 displayed and the unit reports excessive water usage or continuous flow when no taps are open	Continuous Flow / Possible Leak Detection	View Details
F09	F09 error and the unit cannot enter service mode after regeneration	Valve Home Position Not Detected	View Details
F10	F10 displayed and the softener reports high internal pressure or shuts down unexpectedly	Overpressure / Pressure Sensor Fault	View Details
F11	F11 error and the unit aborts regeneration during brine fill or rinse	Drain Line / Backwash Flow Fault	View Details
F12	F12 displayed and the unit reports resin capacity error or cannot calculate remaining capacity	Resin Capacity / Programming Error	View Details
F13	F13 error and the unit indicates brine tank overfill or high water level	Brine Tank Overfill / Float Fault	View Details
F14	F14 displayed and the unit reports communication error between display and main board	Internal Communication Fault	View Details
F15	F15 error and the softener reports sensor supply fault or multiple sensor errors simultaneously	Low Voltage Sensor Supply Fault	View Details
–	Brine tank fills with water and overflows periodically without any error code	Brine Tank Overfilling	View Details
–	Display is on but buttons do not respond or respond intermittently	Keypad / User Interface Fault	View Details
–	Noticeable drop in water pressure at taps when softener is in service	Flow Restriction Through Softener	View Details
–	Softener allows hard water through during regeneration (no soft water bypass)	Incorrect Bypass / Plumbing Configuration	View Details
–	Softener causes water hammer or banging noises in pipes during regeneration	Hydraulic Shock During Valve Switching	View Details
–	Softener display is completely blank and unit is unresponsive	No Power to Control	View Details
–	Softener does not draw brine during regeneration but no error code is shown	Silent Brine Draw Failure	View Details
–	Softener does not start regeneration at the expected time (time-based model)	Regeneration Scheduling Issue	View Details
–	Softener emits a persistent beeping or alarm tone without a visible error code	Hidden Alarm / Service Reminder	View Details
–	Softener emits unusual odour from brine tank or softened water	Bacterial Growth / Contamination	View Details
–	Softener frequently trips the electrical circuit breaker or blows fuses	Electrical Overload / Short Circuit	View Details
–	Softener installed but water remains hard because unit is in permanent bypass	Bypass Left Engaged After Installation or Service	View Details
–	Softener installed on hot water line by mistake, causing deformation or leaks	Incorrect Installation on Hot Supply	View Details
–	Softener leaks water from around the control head or top of the resin cylinder	Control Head / Tank O-Ring Leak	View Details
–	Softener makes loud clicking or grinding noises during regeneration	Drive Motor / Gear Train Wear	View Details
–	Softener never regenerates on a metered model, even with high water usage	No Demand Regeneration	View Details
–	Softener produces salty-tasting water immediately after regeneration	Insufficient Rinse After Brine Draw	View Details
–	Softener regenerates too often, sometimes daily, even with low water usage	Over-Frequent Regeneration	View Details
–	Softener resin tank sweats or shows condensation, with occasional drips onto the floor	Condensation on Cold Surfaces	View Details
–	Softener uses salt very quickly and brine tank empties frequently	Excessive Salt Consumption	View Details
–	Water leaking from brine line connections or around the brine well	Brine Line / Fitting Leak	View Details
–	Water remains hard at taps even though the Vaillant softener appears to run normally (no error code)	Loss of Softening Capacity	View Details

Vaillant Water Softeners Error Codes

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