The first primary part of both kinds of water heater is the heavy steel tank. Capable of carrying between 40 and 60 gallons of water, water heater tanks are equipped to handle water at 300 psi, although in practice it never gets much higher than 100 psi. In order to prevent rust from getting into the water, water heater tanks have a lining of bonded glass. They are also incredibly well insulated to maintain heat efficiency. Electric tanks are typically smaller than those powered by natural gas.
This is the pipe on both kinds of water heater where the cold water enters into the tank. Located at its top is a shutoff valve to stop the flow of water into the tube and the tank. The dip tube extends almost to the bottom of the tank to deposit cold water at the low point.
This is the pipe through which the heated water leaves the tank. It is much shorter than the dip tube, for as water heats it rises. Cold water settles to the bottom, is heated and then makes its way out of the tank.
Thermostat or Burner Control
Electric water heaters have a thermostat, often one per heating element. Gas water heaters use a burner control. In both cases they are designed to control the temperature of the water in the tank.
Heating Elements or Burner
Heating elements jut into an electric water heater from the side. Similar to heating elements on an electric oven, they are thick rods that heat up when supplied with electric energy, thereby heating the water.
In a gas water heater, a burner sits at the bottom of the tank to heat the water. There is also a chimney running through the middle of the tank in gas water heaters.
Both kinds of water heater have a drain valve near the bottom. With this open, the water drains out, allowing you to do repairs or move the entire appliance.
Pressure Relief Valve
So that the water heater tank does not build up too much pressure and risk explosion, a pressure relief valve is necessary. Attached near the top, it is linked with an overflow tube in case too much water is in the tank.
In addition, electric water heaters have what is called a sacrificial anode rod. This is a vertically-placed rod running through the middle of the tank which prevents the tank from water corrosion. These 7 primary parts are found on all electric or gas-powered water heaters. Solar powered or geothermal water heaters incorporate different parts, but by and large electric and gas water heaters are predominantly found in homes and businesses.