Is your water heater making a rumbling noise? Maybe you hear a popping noise or other noise that water heaters should not be making. The reason your water heater is making noise is that it has sediment in the bottom of the tank.
The noise issue typically happens only with gas water heaters because it has the burner under the tank. So when the sediment builds up, it comes to rest on the bottom of the tank. The bottom of the tank is dome-shaped and so it rests around the perimeter first, and then builds up along the bottom of the tank. The noise occurs because water gets trapped in the sediment and gets very hot. It can turn to steam and cause the rumbling sound along with vibrations. Sediment also makes your water heater operate inefficiently. In order for your water heater to produce hot water, it has to heat the water in the tank. The sediment is a layer of sludge that has to be heated first, and then transfers the heat to the water in the tank. If the sludge wasn’t there, the water would get the benefit of direct heat from the burner, instead the heat has to travel through the sediment first. The answer is routine flushing of your water heater to prevent the sediment from building up in the first place.