Digital Harvey water softener shows E01 and will not start a regeneration cycle

Safety first: Turn off the mains water supply and isolate electrical power to the softener (unplug or switch off fused spur) before disconnecting any hoses.

• Check inlet isolation valve: Ensure the Harvey inlet valve on the bypass set is fully open (handle in line with the pipe). If the unit is on bypass, return it to service position.
• Inspect inlet hose: Look for kinks, sharp bends, or crushing on the flexible hose feeding the softener. Straighten or re-route as needed.
• Clean inlet strainer: Many Harvey installation kits include a small mesh strainer at the inlet. Shut off water, unscrew the union, remove the strainer, rinse under running water, and refit carefully with the O-ring seated correctly.
• Check mains pressure: Open a nearby cold tap. If flow is very weak or absent, the issue is with the house supply, not the softener. Restore normal supply before retrying.
• Reset the unit: Restore power, then follow the Harvey user manual to clear E01 (usually by pressing and holding the reset or program button for several seconds) and initiate a manual regeneration to confirm normal operation.

If E01 returns immediately despite good water flow and a clean strainer, the internal flow sensor or control valve may be faulty and a professional technician should inspect it.