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Why a Water Heater Rumbles, Pops or Bangs

It is not the tank about to burst. It is water flashing to steam underneath a layer of mineral that should not be there.

Answer first

The rumble is steam escaping from beneath a layer of sediment on the tank floor. It means the burner is heating sediment rather than water, which costs both efficiency and capacity, and it shortens the life of the tank by overheating the steel.

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What the noise is

Minerals settle out of the water and collect in the bottom of the tank. On a gas heater the burner is underneath that layer, so it heats the sediment rather than the water. Pockets of water trapped in the sediment flash to steam and force their way up through it, and that is the rumble or the series of pops.

What it costs you

Three things. The volume the sediment occupies is capacity you no longer have. The layer insulates the water from the burner, so the heater burns longer for the same result. And the tank bottom runs hotter than it was designed to, which shortens its life.

Where the minerals come from

From the water supply. Harder water deposits more, faster, which is why the same heater lasts differently in different towns.

What can be done

Draining sediment is routine maintenance on a heater that has been kept up with. On one that has rumbled for years it is less straightforward — a drain valve that has never been opened can fail to close again, and a heavily scaled tank may not drain at all. That is worth a contractor rather than a first attempt.

Know the fuel and the symptom? That is most of the call.Gas and electric heaters fail in almost entirely different ways, so saying which you have gets you to the right person faster. We route the call and never charge you for it. Water heaters are what we write about; the number goes further.

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