Control panel displays E01 and the softener does not start a regeneration cycle

Safety first: Turn off electrical power to the softener and close the inlet and outlet isolation valves before disconnecting any pipework. Depressurise by opening a nearby tap.

• Check inlet isolation valve: Ensure the main inlet valve feeding the Monarch softener is fully open. Many Monarch units have a three-valve bypass set; confirm the inlet and outlet valves are open and the bypass valve is closed.
• Inspect inlet hose/pipe: Look for kinks, sharp bends, or crushed sections on the flexible hose or copper pipe feeding the control valve. Straighten or replace as needed.
• Clean inlet strainer: On many Monarch control valves there is a small mesh strainer at the inlet. Isolate the softener, remove the inlet union, carefully pull out the strainer, rinse under running water, and refit. Do not damage the mesh.
• Check mains pressure: If household pressure is very low, the valve may not sense adequate flow. Confirm with a pressure gauge or by checking other taps. If pressure is normal and E01 persists, the inlet flow sensor or valve body may be faulty.
• Restore service: Slowly reopen inlet and outlet valves, check for leaks, then restore power and attempt a manual regeneration from the control panel.