How a Tankless Water Heater Works

Tankless water heaters work very differently from tanked water heaters and therefore have different parts. Instead of holding hot water in a large tank, the water heater only kicks on when there is a demand for hot water, like when a shower or tap is turned on. So, instead of heating the water all day and night, the tankless water heater is off until it is needed.

Inside the tankless system, a burner ignites when the system signals a need for hot water. The cold water passes over an aluminum heat exchanger and heats the water directly. When the hot water is shut off, the system goes into standby mode. A tankless water heater also has a vent that exhausts any gases outside the home.

Here are some gifs to illustrate how a tanked water heater and a tankless water heater work.

how tank water heater works how tankless water heater works

To help you understand better how a tankless water heater works, here is a list of steps:

STEP 1 - Hot water tap is turned on

You want to make sure that hot water is flowing through your pipes, this means turning on the hot water. Of course, today that isn’t always a simple explanation. If you have a single knob, be sure to turn it towards the hot water. If you have dual knobs, it’s much simpler. Locate the hot water knob, and turn it to allow the hot water to flow through.

tankless water heater - turn hot water on

STEP 2 - Water enters the heater

So, now that you have the hot water turned on, what should you expect? With a regular water heater, you expect hot water to travel from the tank through your pipes. However, with a tankless water heater, cold water actually flows through sensors that trigger the internal computer, and begin the heating process.

tankless water heater - water enters heater

STEP 3 - Water flow sensor detects the water flow

Now that the internal computer has been triggered, it immediately calculates how hot the burners need to be, in order to heat the water to the perfect temperature. This can be done with a gas burner or an electrical element. Either way, it provides a constant flow of hot water, without having to wait for a tank to fill back up.

tankless water heater - water flow sensor detects water

STEP 4 - Computer automatically ignites the burner

So how does the tankless water heater actually provide all that hot water? After the burner begins heating the water, it circulates around a heat exchanger until it reaches its designated temperature. From there, the water exits the tankless water heater and begins traveling through your pipes until reaching its final destination.

tankless water heater - computer ignites burner

STEP 5 - Water circulates through the heat exchanger

With a tankless water heater, you enjoy an endless stream of hot water to use. Once the demand for hot water no longer exists, the tankless water heater automatically shuts down and stops using energy. So, you get to enjoy energy savings along with constant and fresh hot water.

tankless water heater - water circulates through exchanger

When making a decision on whether or not to switch to a tankless water heater, it’s important to know how one works. Along with knowing how it works, you also want to know what the benefits of having a tankless water heater would be as well. Having a steady stream of hot water is just one benefit. However, a lot of people also enjoy the money savings with a tankless water heater because it uses less energy to operate than a tanked one.