How does a water heater (geyser) work?

A geyser is a flask with a 2 kW heater inside, and it quietly uses physics you can feel in the shower: hot water floats, water expands, and a magnesium rod dies to save the tank. A storage geyser is a steel tank lined with glass, wrapped in foam and hung on the wall.

Read how it works: How does a water heater (geyser) work? · The history of the water heater · More boxes on Glassbox

Chapters in this interactive model

1. Inside a geyser: A steel tank wrapped in foam, with a hot rod inside and a clever valve below.
2. How long does it take?: Mass, specific heat and a temperature rise: the sum behind the wait.
3. Hot water floats: Why the tap runs hot, hot, hot, then suddenly cold.
4. The thermostat and the safety chain: One switch does the work; three more stand guard in case it fails.
5. Rust and scale: A rod that dies so the tank can live, and the stone that grows on a hot element.
6. Energy, stars and cheaper hot water: A hot tank leaks heat all day. Here is what that costs, and the alternatives.