Lochinvar water heater makes loud popping or rumbling noises during heating.

Safety: Turn off power or gas and allow the heater to cool. Close the cold water supply and relieve pressure by opening a hot water tap.

Steps:

• 1. Flush tank-type heater: Connect a garden hose to the drain valve, run to a floor drain, and open the valve. Briefly open the cold supply to stir sediment, then drain again until water runs clear.
• 2. Descale condensing models: For Lochinvar condensing water heaters, use a pump and approved descaling solution to circulate through the heat exchanger per the service manual.
• 3. Adjust temperature: Lower the thermostat or setpoint to reduce scale formation (e.g., from 140°F to 120°F if acceptable).
• 4. Consider water treatment: Install a water softener or scale reduction system if hardness is high to prevent recurrence.