The answer to 'water heater making loud noise' is that a noisy water heater is often a sign of a serious problem that requires professional attention. Common causes include sediment buildup, mineral deposits, or a failing heating element. Symptoms can include rumbling, popping, or banging sounds coming from the tank.
While some minor issues like flushing the tank may be a DIY fix, it's generally best to call a licensed HVAC technician to diagnose and repair a noisy water heater. They have the expertise to properly inspect the unit, identify the root cause, and make any necessary repairs or replacements to restore safe, quiet operation.