Richmond water heater makes a high-pitched whistling or screeching noise when hot water is running.

Safety first: Noise itself is not dangerous, but hot water can scald—use caution.

• Check valves: Ensure the cold water shutoff to the heater and any outlet valves are fully open.
• Clean inlet screen: Remove and clean the cold water inlet filter on tankless models.
• Inspect mixing valve: If a thermostatic mixing valve is installed, clean or replace it if internal parts are worn or clogged.
• Check fixtures: Clean or replace noisy faucet cartridges or shower valves that may be causing the whistling.