How Does A Tankless Water Heater Work?

How Does A Tankless Water Heater Work?

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If you grew up in a large household, you must know how disappointing it can be when you want to take a shower, but the big tank is out of hot water.

Imagine having to wait close to half an hour to shower when you have a meeting to catch?

Well, thanks to a tankless water heater, the waiting to take a bath is now a thing of the past for most people. So, how does a tankless water heater work, and what makes the unit stand out?

Tankless Water Heater Basics

A tankless water heater starts when you activate it. Thanks to its flow sensor, the heater will sense when you turn the hot water tap on, and it will automatically start producing hot water.

Unlike tank-based heaters that store up a certain amount of hot water, the amount produced in the tank-less version is based on demand.

This makes the tankless heater more efficient.

You will not have gallons of hot water sitting in the tank while you are at work or run out of water when the whole family wants to shower in the morning.

How Does A Tankless Water Heater Work- Gas vs Electric?

Gas-fired tankless heater

If the tankless water heater is gas-fired, the control panel turns the fan on, which draws enough air from the outside to open the gas valve.

The open gas-valve allows gas in, and the burner ignites so that water passing through the exchanger tubing is adequately heated.

There is a mixing valve that tempers the water so you can get it at the temperature you want.

Also Read: 5 Easy To Spot Signs of a Busted Water Heater

This tank also comes with a temperature sensor responsible for detecting if the water falls within the desired setting. If this is not the case, the sensor will adjust the gas, mixing, and flow-regulating valves to ensure that the water getting out of the tap is at the desired temperature.

There are also one or two sealed vents that extend to the roof or an outside wall. These carry out the exhaust gases while allowing combustion air into the burner.

Electric tankless Heater

This one works just like the gas-fired one. The only difference is the source of fuel, and since the wiring is done with such appliances in mind, the installation is much simpler.

Aside from how does a tankless water heater works, there will be other questions about this heater that may cross your mind.

There are some of the commonly asked questions:


Tankless electric heaters come in a variety of prices, so you are guaranteed to get one that will fall within your budget.

Gas-fired units tend to be slightly pricier when compared to electric ones.

A tankless gas-fired water heater may cost anything from $170 or thereabout to over $2000. Anything below $200 is small and only ideal for single person use.

If you are looking for a heater that can supply adequate water for two showers, you may need to check within the $1000 range.

For an electric heater, costs fall between $90 and $1000. However, there will be other costs incurred during the first-time installation process.

Installation Process

Again, this is dependent on the type of tankless water heater. Each type comes with its installation instructions which must be followed to ensure efficiency and durability.

It is always wise to involve a professional who can ensure that your heater is installed. For gas heaters, the gas connections and vent must be done right while an upgrade in the wiring and circuit-breaker panel may be necessary.


If possible, get an installer who also does maintenance so you can discuss maintenance routine when installing the water heater.

In this case, maintenance includes changing/cleaning water filters, checking the burner, and taking care of any mineral buildup.

If you live in an area with hard water, you should do a vinegar flush after every 500 hours. This will keep mineral buildup at bay and protect the heat exchanger against clogging.

The vinegar flush can be done without professional help, and it will take you half an hour or less to complete. Just follow the instructions given by the water heater manufacturer.


If you get the gas tankless heater, you should expect at least 20 years of continued service. This is two or three times the duration you get with the tank heaters.

The electric tankless heaters last about seven to ten years. Even with a shorter lifespan, these heaters can’t be compared to the tank ones in terms of reliability.

Tankless Water Heater Pros


Want hot water in your tap in a minute or less? The tankless water heater got you covered.

You can also have your entire family showered and still have hot water for your washing machine and dishwasher.

With the tankless water heater, you save on time and energy bills, making it ideal if you are looking for a more efficient home.


A tankless water heater is about the size of a suitcase. They can fit in the tiniest of spaces and even hang comfortably against a wall.


There are chances of leakages and spillage. You do not have to worry about a tipped over tank after an earthquake or using water that has been harboring bacteria for ages.

During installation, the exhaust and air supply vents are well sealed.

This makes it impossible for carbon monoxide to leak back into the house as a result if back drafting.

Easy to drain when necessary

If you have a vacation home, you must be aware that draining a tanked water heater takes a long time.

For the tankless one, all you need is a few seconds, and you can then unplug the heater until you are back to the home again.


Doesn’t work properly in low pressure

When answering how does a tankless water heater work question, we highlighted that this type of heater starts when the switch on button is activated.

Imagine a case where building up in the pipes reduces the water flow, or the faucet or showerhead is clogged. If the water passing through the exchanger tubing isn’t enough, the heater will automatically go off.


You may need about $1000 to get a quality tankless water heater. However, the benefits in the long run by far outweigh the cost.

Also Read: Proven Tips to Prevent Water Heaters Overheating

A tankless water heater will save you a lot in energy bills. Additionally, there is little chance you will need to repair or have any parts replaced after installation.

It is also true that tankless water heater units last longer. You may need to save a little more to get the tankless unit. However, your investment will be well worth it.


Now that you know how the tankless water heater works, you can make an informed decision on which option to pick when you want to upgrade your tank water heater.

You can be sure that the tankless heater will be more effective in the short run and better for your pockets in the long run.