Rumbling or popping: sediment
This is by far the most common. Minerals settle out of the water and form a layer on the bottom of the tank. Water gets trapped underneath and boils through the sediment, which makes the popping and rumbling. It also insulates the burner from the water, so the tank works harder and costs more to run. Flushing usually clears it.
Screeching or whistling: a restricted valve
High-pitched noise generally means water forcing through a partially closed valve, often the inlet valve or the temperature and pressure relief valve. A T&P valve that whistles deserves immediate attention because it's a safety device.
Ticking or tapping: normal expansion
Metal expands as it heats and contracts as it cools, and pipes tick against their strapping. This one is usually harmless, though it can be reduced by adjusting how the pipe is supported.
Hammering when a tap closes: water hammer
A bang in the pipes when a faucet or appliance valve shuts is water hammer, caused by moving water stopping abruptly. Over time it stresses joints and fittings. Arrestors resolve it.
What noise means for the tank's remaining life
Sustained rumbling on a tank past ten years is worth taking as a signal rather than a nuisance. Sediment accelerates corrosion of the tank bottom, and once the steel goes through, replacement is the only option — usually on the day it happens rather than the day you planned.
If the tank has started talking to you, a flush and an honest assessment of its remaining life costs very little. We service and replace water heaters across Michigan. Call (888) 809-6756 any hour, or read more about Water Heater Repair in Michigan.