Water heaters are familiar fixtures in most homes. That's because the water coming into your home makes a journey through a system of pipes, and it's usually cold or cool, depending on the time of year. To have water warm enough to take a shower or bath or wash clothes, you need a water heater.
They typically look like big metal cylinders and they're often confined to a utility room or basement. Newer styles have some interesting features, like tankless water heaters that provide endless hot water on demand.
But the old, reliable water heater design that's most widely used in the U.S. today is really a pretty simple appliance; it's basically a drum filled with water and equipped with a heating mechanism on the bottom or inside. Common energy sources for heating up water include electricity, burner oil and natural gas. Some modern applications have also moved to solar and geothermal heat for increased efficiency.
What makes water heaters interesting is that they exploit the principle that heat rises to deliver hot water right to your faucet with minimum fuss. Don't let the simple shape shrouded in its wooly insulating blanket fool you. Water heaters have an ingenious design on the inside for something that looks so ordinary on the outside.