Marey heater produces a whistling or high-pitched noise during operation.

Safety first: For gas adjustments, use a licensed technician.

Steps:

• Check water valves: Ensure inlet and outlet water valves are fully open. If noise persists, slightly throttle flow to see if pitch changes.
• Inspect aerators: Remove and clean faucet aerators and showerheads; debris can cause whistling.
• Gas supply: Have a gas technician verify that the gas valve and regulator are correctly adjusted and free of debris.

When to call a technician: If noise is loud, new, or accompanied by performance issues.