How does a hot water heater work? Very few people ever ponder the answer to this question. Most people just expect hot water to appear after turning the faucet on and allowing the water to run for a few minutes.
Hot water heaters, be it electric or gas, have many parts in common. These are a heavy inner steel tank, insulation, a dip tube, a pipe, a thermostat, a drain valve, a pressure relief valve and a sacrificial anode rod and of course, a heating apparatus. All these parts work together to heat water and move it to the correct spigot.
Gas water heaters are not that different from electric water heaters but they do have a gas burner located in the bottom of the tank and a chimney that runs up through the middle of the tank instead of two heating elements. The heating elements located in electric hot water heaters are installed with one almost in the center of the tank and the other one about one-quarter of the way from the top of the tank.
The heavy inner steel tank typically holds 40 to 60 gallons of water and is tested to hold a pressure of 300 pounds per square inch (psi), making it capable of holding the pressure of a residential water system, which is usually 50 to 100 psi. This inner steel tank is also built to hold heated water that will range from 120 to 180 degrees, depending on the setting.
Setting the thermostat in this range prevents scalding of little children and saves energy. A thermostat, generally located underneath a cover plate, controls the temperature by using a knob or a screw. These steel tanks also contain a sacrificial anode rod that keeps the steel tank from corroding; bonded glass liners located inside the tank keep out rust and they are insulated.
A pipe enters the steel tank from the top and runs down through the tank to the bottom portion allowing cold water to enter the tank. This pipe also has a cut-off valve located at the top of it before entering the tank. Another pipe enters the tank at the top and only runs a short distance to allow the hot water to exit the tank.
Also, located on the bottom of the tank is a drain valve, which allows for draining of the tank in case it has the tank that has to be repaired or removed. A pressure relief valve is located on the top of the tank also and has an overflow pipe attached to it that keeps the tank from exploding. Hot and cold water are separated in the tank by the hot water rising to the top of the tank and denser cold water remaining at the bottom of the tank where it enters the tank.
If a person runs out of hot water while in the middle of a shower, one of several things could have happened. One, the hot water was used faster than the heating elements could heat incoming cold water. Two, the bottom-heating element could be burned out on an electric water heater.
Three, the water heater is too small for the household. Four, the person could be taking really long showers.