Hi PeterThor, thanks for reaching out. Yes, this sound is perfectly normal and is simply the tank adjusting to maintain its set temperature. This sound will occur periodically throughout the heating cycle, approximately every 45–60 minutes. If you are using the hot water regularly, you will hear a rumbling even more often because the tank will be heating up to temperature. You can try to lower the temperature in the tank slightly. Locate the thermostat dial on the front of the tank and turn it 1/2 a notch counterclockwise to decrease the temperature. Then dispense water for 20 seconds to allow cold water to enter the tank. Allow the water to reheat to the new setting. You can continue adjusting the dial in small increments until the temperature is to your liking.
2 weeks, 1 day ago
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InSinkErator