Does your water heater make a rumbling noise?

A rumbling water heater is usually caused by a buildup of sediment in the bottom of the tank:

Sediment buildup

Minerals like calcium and lime from the water settle out and build up over time, covering the heat exchanger. When the water is heated, it forces its way up through the sediment, which can be noisy.

Overheating

Sediment buildup can lead to overheating, which can shorten the life of your water heater and cause water damage.

Too much cold water

When too much cold water enters the tank at once, it can cause a rumbling sound.