How does a tank water heater work?

Heating water and keeping it warm isn't as simple as it might seem.
A tank water heater is just that — a tank that heats water. But how does it work exactly?

Water comes from the water lines in your home and enters through the top of the tank and travels through a tube to the bottom of the tank. As the water is heated, it rises to the top of the tank. The hot water is released through a pipe located at the top of the water heater tank when you turn on your hot water faucet.

And just how is the water heated?


Source: U.S. Department of Energy
Natural gas and propane water heaters have burners under the tank that heat the water. A thermostat opens a gas valve as the water temperature drops and closes the valve when the water temperature reaches the thermostat setting. Oil-burning water heaters have power burners that mix oil and air into a vaporizing mist, which is ignited by an electric spark. Electric water heaters have one or two heating elements, each with its own thermostat.

Tank water heaters need a little care from time to time, though. Remember to always check your owner's manual and take proper safety precautions when working around your water heater.

See this explainer on how to keep your tank water heater running smoothly.

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