E10 error and unit will not enter regeneration when commanded

Safety first: Ensure the unit is plugged into a grounded outlet and is dry around all electrical components.

• Check programming: Enter the installer menu and verify that regeneration is not disabled by a service lockout or vacation mode.
• Verify time/day: Confirm the time-of-day and day-of-week are correct. Some Waterguy models will not regen if the clock is invalid.
• Inspect lid switch: If your model has a brine tank lid or cabinet switch, ensure the lid is fully closed and the switch actuator is not broken. Bypass the switch temporarily (for testing only) to see if E10 clears.
• Manual regen: Attempt to start a manual regeneration. If the display shows E10 immediately, the control board may be detecting an internal fault.

If all interlocks are verified and E10 persists, the Waterguy control board likely requires replacement.