What’s Going on Inside Your Water Heater?
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Hot showers, clean dishes, warm laundry—your water heater quietly powers some of the most comforting parts of home life. But here's something surprising: according to the U.S. Department of Energy, your water heater accounts for nearly 18% of your home's energy use. Despite its importance, most homeowners rarely think about how their water heater works—until something goes wrong.
In this post, we'll take you behind the scenes to explore water heater anatomy, explain the difference between tank and tankless models, and help you spot signs of trouble before they turn into cold showers.
What You'll Learn in This Post
By the end of this article, you'll understand:
- How tank and tankless water heaters work
- What's going on inside your water heater
- Common signs of trouble (and how to fix them)
- When to call in the experts
Water Heaters 101: The Basics
So, let's start at the beginning and answer the most basic question: What does a water heater do?
A water heater...
- Heats cold water coming into your home.
- Stores or delivers hot water to fixtures and appliances inside your home (dishwasher, shower, laundry machine).
However, the way it heats depends on the type of water heater you have.
Now that we've covered the basics, let's look at the two main types of water heaters and see how they differ.
Tank v. Tankless Water Heaters: What's the Difference?
The two most common types of water heaters are those that heat water on demand and those that store it in a tank. Here's a brief overview of water heater anatomy and a comparison of the two types.
Traditional (Tank) Water Heater
A traditional tank stores between 20 to 80 gallons of water in a large, insulated tank (you'll know if you have a tank because it's tall and cylindrical and is probably in a utility room or the garage). It uses electric elements or gas burners to maintain temperatures.
- Pros:
- Lower initial cost
- Water is heated consistently to offer multiple uses at once
- Cons:
- Hot water can run out after heavy use
- Uses standby energy to keep water hot 24/7
Tankless (On-Demand) Water Heater
The tankless model heats water on demand. Therefore, it only heats water when in use. It uses high-powered gas burners or electric coils as water passes through the unit.
- Pros:
- It is highly energy-efficient, eliminating standby heat loss.
- Offers an endless supply of hot water.
- Saves space because there is no tank
- Cons:
- Higher upfront installation cost
- May struggle to handle multiple fixtures running simultaneously (such as a shower and dishwasher operating together).
Gas vs. Electric Water Heaters
The primary difference between gas and electric water heaters lies in their method of generating heat. Gas models use combustion while electric models rely on heating elements.
Gas Water Heaters
- Use a gas burner (like a stove flame) at the bottom of the tank
- Requires ventilation for exhaust gases
- Typically heats water faster
Electric Water Heaters
- Use one or two heating elements inside the tank
- Controlled by an external thermostat
- Often more energy-efficient but slower to heat
How a Water Heater Works: Inside the Tank
Curious how hot water happens inside a gas water heater or an electric model?
The process of heating water is quite simple and utilizes the scientific principle that warmer objects rise and colder objects sink.
Inside your water heater, cold water enters through a dip tube that directs it to the bottom of the tank. There, it's heated by electric elements or a gas burner. As the water warms, it rises to the top—ready to flow whenever you open a hot-water tap.
If your water heater is not working, these are some of the most common culprits:
- Pilot light is out
- Pressure relief valve is failing
- Interior of tank has mineral or hard water buildup
- The anode rod needs to be replaced (an anode rod helps prevent corrosion).
Common Hot Water Heater Q & As and What to Do
Why don't I have any hot water?
Common reasons for no hot water include a pilot light that has gone out, a tripped breaker, or a failed element. Check the pilot light and your breakers. If these troubleshooting steps don't resolve the issue, please contact us for service.
Why is my water too hot/cold?
A faulty thermostat or sediment buildup may be the cause for this. Adjust your thermostat (set between 120 and 125-degrees F) and schedule a tank flush.
Why is my tank leaking water?
This could be caused by corrosion or a failing pressure valve. Turn off your power and water and call us ASAP for service.
Why am I hearing strange noises?
If you're hearing strange noises inside your water heater, you may have sediment buildup. We recommend draining and flushing the tank.
Why is there rusty water near my water heater?
You may have a corroded tank or a faulty anode rod. Call us! We can assess the problem and replace the anode rod if that is what's needed.
Still Having Trouble? Here's When to Contact an Expert
Here's when it's time to call in the pros to take a look inside your water heater.
Call an experienced plumber if you notice:
- Persistent leaks
- Discolored or rusty water
- Inconsistent hot water supply
- Pilot or burner issues
Don't let water heater issues ruin your holiday season! Schedule your water heater service with A.J. Perri today!