How does a Hot Water Heater Work?

Have you noticed that we worry about how house appliances work only when they malfunction or break?

And yet, knowing how they work could help us maintain them more properly and avoid at least some of those malfunctions.

Furthermore, knowing the components and how they work could also help us avoid service providers from fooling us and asking for too much money. 

Also, according to Legacy Plumbing, About 17% of the energy used in your home goes toward heating your water. So learning about water heater can help you save on that electricity bill too.

So iIn this article, we’re focusing on water heaters: how does a hot water heater work?


Components of a Water Heater

Water Heater: Components

If you want to understand how a hot water heater works, you must first understand the components.

So this is a list of the main components of any hot water heater:

  • Tank: The tank is the component of the water heater that stores the water. This way, as soon as you open a faucet in the house, the hot water will be immediately available.
  • Dip Tube: the dip tube is where the water comes inside your house. It’s the beginning of your water line: the municipal water source provides water to your house through the dip tube. From there, the water enters the hot water heater unit.
  • Heating element: it’s the element that provides heat so that the water can be warmed. It can be electrical or a flame. If you see flames in your water heater, you have a gas water heater: it is connected to the gas supply, and the gas feeds the small flames that heat the water.
  • Anode Rod: a safety measure that prevents the tank from rusting because of electrolysis
  • Thermostat: it’s the elements of the water heater that “reads” the temperature of the water and regulates the heating element according to it.
  • Valves: last but not least, in your water heater, you certainly have more than one valve:
    • the drain valve, which is used to drain the sediments that can build up inside your tank;
    • the shut-off valve can be turned to avoid more water entering the tank.
    • Pressure relief valve. The water inside the tank has pressure, and the valve prevents the pressure from getting too high, which would be extremely dangerous. 1

Read: How Does A Tankless Water Heater Work?

Also Read: 10 Best Immersion Heaters 

How does an Electric water heater work?

So, what mechanism allows you to have hot water in your shower?

From the dip tube, the municipal water enters your water heater unit. Water that runs through the unit gets heated thanks to the heating elements that could be electrical or gas-feed (flames).

Then, the hot water would be stored in the water tank. From here, many tubes have connected that end up in every faucet in your house.

This way, whenever you need hot water, you can turn on your hot water faucet, and the hot water will be immediately available.

What happens when the tank runs out of hot water? You still have water running through your faucets, but it would be cold.

To have hot water again, you’ll need to wait: the water needs to get heated by the heating unit, and the tank needs to be filled again. Then, you can have hot water again. 2

Here’s what Reddit users think

ELI5: How do hot water heaters work?
by u/nathanialox in explainlikeimfive

Read: 10 Best Dewalt Heaters

How Does a Tankless Water Heater Work?

tankless water heater

Tankless water heater works in a rather unconventional way and is gaining popularity due to their unique heating mechanism.

A tankless water heater does not require heating up the entire tank each time it’s used. Instead, it heats the water only when needed.

So what is the heating mechanism of a Tankless water heater? When you turn on the hot water tap, a sensor unit inside the heater activates.

So if it is an electric tankless water heater, then the sensor on the electric heating unit gets activated, and if it’s a tankless gas heater, then the sensor inside the unit turns on a fan which is situated inside, that opens the gas valve and ignites the burner.

In either type of tankless water heater, the heated unit heats the water that passes through the unit into the tap, and this is how you get hot water on demand.

Because tankless water heaters do not work by heating up an entire tank, you end up saving a lot of energy, and this is the reason why homeowners have started to switch to a tankless water heaters. 3

How Does a Gas Water Heater Work?

Gas water heaters are equipped with a thermostat, which is a compact copper tube attached to a mercury sensor.

They also contain a special sensor called “Thermocouple,” which is supposed to sense whether or not the pilot light is ignited.

If the pilot light is not burning, then the thermocouple sensor does not let the gas flow down the burner.

So when cold water in the tank falls, the thermostat starts sending a signal that goes to the gas control valve, which in turn checks the signal from the thermocouple to make sure that there is a pilot light.

If this is the case, then the valve opens up to allow the gas to pass through the burner, which then ignites the flame.

This flame starts heating up the bottom of the tank, which causes cold water to heat up.

The heated water starts rising up, and the remaining cold water goes to the bottom to get heated up.

This cycle continues till the desired temperature is achieved. And this is how a gas water heater works. 4

How Does a Hybrid Water Heater Work?

So a hybrid water heater contains a tank that is equipped with an electric heat pump. The water storage tank of this heater contains a pump that is mounted on top of the heater.

This pump uses an evaporator coil and a compressor that captures hot air present in the room and then uses it to heat the incoming cold water.

Homeowners have to pay a high upfront cost for hybrid water, but due to its working model, it uses 60% less energy when compared to a conventional water heater.

Tips For Water Heater Maintenance

Here are a few tips that will help you maintain your water heater:

  • Flush your water heater tank annually to avoid any sediment buildup. Otherwise, your heater will not last long.
  • Choose a safe temperature for the thermostat in the water heaters. Experts recommend 120 degrees for best results.
  • Keep a check on the anode rod, and make sure to replace it when it starts corroding. 5

Wrap Up

Water heaters are great investment options, and they are available in such wide varieties to suit the needs of different people and their households.

In this article on how a Hot Water Heater work, we explained to you the working mechanism of electric, gas, and hybrid water heaters. We hope you found this useful.


What is the most common issue with water heaters?

If not checked and maintained, water heaters can lead to water leaks, which is the most common issue.

Can I take a shower even when my water heater is leaking?

We suggest you get the issue fixed first. This would avoid any further damage and potential accidents.

Are tankless water heater expensive?

Tankless water heaters have a higher upfront cost than an electric water heater, but they can help you save electricity and electricity bills.

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