A water heater making noise is telling you something. Match the sound to the cause.
Popping or rumbling
Sediment has settled on the bottom of the tank. Water trapped under it boils and bursts through. It is the most common noise and a sign the tank needs flushing. Left alone, the sediment overheats the tank bottom and shortens its life. Hard water makes it worse, which is where a water softener helps.
Banging or hammering
This is usually water hammer in the pipes when a valve closes quickly, not the heater itself. Arrestors or a pressure check solve it.
Hissing or sizzling
On an electric heater, scale on the elements. On a gas heater, condensation or a small leak dripping onto the burner. If you see water, the tank may be failing: read our guide to a leaking water heater.
Whistling or screeching
A partly closed valve or, more seriously, the temperature and pressure relief valve venting. A relief valve that discharges needs attention right away.
Ticking
Normal. Pipes expand and contract as they heat and cool.
What to do
Annual flushing prevents most noise. If the heater is over ten years old, noisy and running out of hot water quickly, compare water heater repair against water heater replacement. Thinking about never running out again? Look at tankless water heater installation.
Common questions
Is a popping water heater dangerous?
Not immediately. It is a maintenance warning. A relief valve that is leaking or discharging is the sign that needs urgent attention.
Can I flush the water heater myself?
Yes, on a tank in good condition: turn off the gas or power, connect a hose to the drain valve and flush until the water runs clear. On an old tank that has never been flushed, the drain valve may clog or leak, so many owners leave it to a plumber.