Ariston electric water heater shows E09 and does not heat; sometimes accompanied by tripping of the breaker.

Safety first: Turn off power at the main breaker. Do not reset an RCD/GFCI repeatedly without finding the cause.

• Inspect for moisture: Remove the front cover and check for water leaks around the element flange, anode, or connections. Dry any moisture and repair leaks before proceeding.
• Test element to ground: With all wires removed from the element, measure resistance between each terminal and the metal tank. Any low resistance (or continuity) indicates a ground fault—replace the element.
• Check power cable and terminal block: Look for burn marks, melted insulation, or loose screws. Replace damaged components.
• Verify correct earthing: Ensure the earth/ground wire is securely connected to the chassis.

If E09 persists after replacing a faulty element and drying the unit, the control board may have an internal leakage path and should be replaced by a professional.