E10 displayed, unit refuses to start; often related to water pressure or flow issues.

Safety: Turn off power and close the cold water isolation valve before removing any water connections.

• Check mains water pressure: Open a cold tap and verify that pressure is adequate. If pressure is low throughout the property, contact your water supplier.
• Clean inlet filter: Isolate the cold water inlet to the heater. Remove the inlet union and extract the mesh filter. Rinse under running water and refit.
• Inspect DHW flow sensor: On many Chaffoteaux models, a turbine or reed-type flow sensor is installed on the cold inlet. Remove it carefully and check for debris or limescale. Clean gently and ensure the turbine spins freely.
• Check wiring to flow sensor: Reseat the connector on the sensor and PCB. Look for damaged cables.
• Test operation: Restore water and power, then open a hot tap fully. If E10 persists, the flow sensor or water valve assembly may need replacement.