Aquabion softener shows E15 and regeneration is locked out due to excessive recent regenerations.

Safety first: Ensure power is disconnected before opening the controller housing.

• Check for leaks: Inspect the home for running toilets, dripping taps, or other continuous water use that could trigger frequent regenerations.
• Verify programming: Confirm that the hardness, capacity, and reserve settings in the Aquabion controller match your water analysis and resin size.
• Flow sensor check: Inspect and clean the turbine flow sensor as described for E01. A faulty sensor can over-report usage.
• Clear lockout: Follow the Aquabion manual to clear the E15 lockout and reset regeneration counters. Monitor the system over several days to ensure regeneration frequency returns to normal.

Warning: Do not simply disable safety lockouts without correcting the underlying cause; this can lead to resin exhaustion and hard water.