A gas heater looks like an electric unit, except that it doesn't contain the two heating elements. It has a gas burner at the bottom, with the chimney running up through the middle of the tank.

HSW 2000

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 hot shower or bath, or use your dishwasher or washing machine, you need a water heater.

Water heaters are familiar fixtures in most homes. They typically look like big metal cylinders, tall drums that are often consigned to a laundry room or basement. Newer styles have some interesting features, like losing the tank completely in favor of 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. Even though they lack drama and complexity, water heaters are still pretty amazing. What makes them interesting is that they exploit the heat rising principle to deliver hot water right to your faucet with a minimum of 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.

In the next pages, we'll get into a little hot water and take a closer look at what's really going on in that big steel can of a water heater in your basement.