An A.O. Smith water heater makes popping or rumbling noises during heating.

Safety: Turn off power or gas and allow water to cool before flushing.

• 1. Flush tank: Connect a hose to the drain valve, open a hot faucet, and drain several gallons. For severe noise, perform a full flush until the water runs clear.
• 2. Descale elements: On electric models, remove and inspect the elements. Replace heavily scaled elements and consider using low-watt-density elements.
• 3. Water treatment: Consider installing a water softener or scale reduction system to prevent future buildup.