Inside a Water Heater

If you were to cut a water heater in half, you would find that it looks something like this (electric on the left, gas on the right):

A gas water heater is nearly identical to an electric water heater, except that it does not contain the two heating elements, but instead has a gas burner at the bottom, with the chimney running up through the middle of the tank.

A water heater consists of the following parts, as shown in the figure above:

• A heavy inner steel tank that holds the hot water
  

  Typically, this tank holds 40 to 60 gallons. It has to be able to hold the pressure of a residential water system, which typically runs at 50 to 100 pounds per square inch (psi). The tank is tested to handle 300 psi. The steel tank normally has a bonded glass liner to keep rust out of the water.

• Insulation surrounding the tank

• A dip tube to let cold water into the tank

• A pipe to let hot water out of the tank

• A thermostat to control the temperature of the water inside the tank (Many electric water heaters have a separate thermostat on each element.)

• Heating elements to heat the water (These are the thick electric elements similar to those you see inside an electric oven.)

• A drain valve that allows you to drain the tank to replace the elements or move the tank

• A pressure relief valve (This is an important safety feature that keeps the tank from exploding.)

• A sacrificial anode rod to help keep the steel tank from corroding

Now let's see how these all these parts work to provide you with hot water.