Unit displays E18; may occur after a long period of inactivity or after service.

Safety: Turn OFF power before attempting to fill or purge the heater.

• Verify water supply: Ensure the cold water inlet valve to the EcoSmart heater is fully open and that upstream shutoffs are not closed.
• Purge air: Open multiple hot water taps to allow water to flow through the heater and push out air. Let water run for several minutes.
• Check installation: Confirm the heater is installed upright and plumb as specified by EcoSmart; incorrect orientation can trap air.
• Reset and test: After purging, turn power back ON and run hot water. If E18 returns, the flow sensor or dry-fire detection circuit may be malfunctioning.
• Service if needed: Replace the flow sensor if it fails to detect flow despite confirmed water movement.