What's Going On Inside My Water Heater?
October 09, 2012
Among the things in your home that you take for granted, a nice hot shower is probably near the top of your list…but how exactly does the water go from chilly to steamy? Water heaters are fairly simple to understand. For most of us, the water heater is a big metal tank, probably in the utility room or garage, in a size somewhere between 20 and 80 gallons. It’s powered by gas or electricity. The difference between gas and electric water heaters is how the water is heated.
- Inside the tank of an electric water heater are two heating elements controlled by a thermostat outside of the tank.
- A gas water heater has a burner inside the bottom of the tank, similar to the burner on a gas stove, controlled by a knob outside the tank. A gas water heater will also have a chimney to allow the heated air from the burner to escape.
The tank actually has three layers: an inner tank where the water is stored, covered with insulating material such as polyurethane foam, and then an outer tank. Inside your tank is the anode rod. The anode rod is made of magnesium or aluminum and has a steel core; it’s suspended inside the tank to help keep corrosion at bay and give your water heater a longer life. Outside the tank you’ll see:
- One pipe that brings cold water into the tank, and another that takes hot water out of the tank. The cold pipe, or dip tube, has a shutoff valve to manually stop the flow of water into the tank if necessary. In normal operation the amount of water that flows into the tank is regulated by the tank’s pressure.
- The pressure relief valve, located on the top of the tank, keeps the pressure within safe limits.
- The drain valve near the bottom of the tank, which can be used to empty it when it needs to be cleaned, if a gas burner needs to be replaced, or if the tank needs to be moved to a new location.
The process of heating the water is quite simple and uses the scientific principle that warmer things rise and colder things sink. Cold water enters your water heater through the dip tube and goes to the bottom, where it’s heated. The hot water then rises to the top of your tank and is continuously heated while it waits to be requested, such as when you take a shower or turn on the dishwasher. If your water heater is not working, some of the most likely culprits include:
- Pilot light is out
- Pressure relief valve is failing
- Interior of tank has mineral or hard water buildup
- Anode rod needs to be replaced
If your water heater experiences problems, the best thing you can do is call a professional plumber for repairs. While a water heater is deceptively simple, a do-it-yourselfer can do more harm than good—especially if the water heater is gas. Armed with the knowledge of how the water heater works, you can get a clearer picture of what a plumber needs to do to bring it back to life.
Last Updated: September 13, 2023