How To Install an Electric Tankless Water Heater

An electric water heater being installed in a home

Can a homeowner install a tankless water heater?

Anyone who has done any DIY know that advance preparation is the golden rule. You never rush into a job without understanding what it involves. And also you should avoid undertaking any tasks which are outside of your personal skill set.

Thinking of installing an electric tankless water heater? Be careful. Be VERY careful. If you’re not already knowledgeable, you should think twice about installing your own electric tankless water heater. It isn’t a job for a novice. Instead hire a professional to do it for you.

Why? Well for a start, nobody likes electric fires, but this is one very easy way to start one. Or you could inadvertently blackout your house. Please, do your research, and if you feel this task is too challenging, take a pro on board.

We do not take any responsibility for any accidents that may occur during this process, all is done at your own discretion.

But if you are going to proceed safely, here is the installation guide.

Let’s start with a basic first few steps. These may not be the most exciting, but they are certainly the most essential. Here are some of the requirements for installation in a residential property.

Can You Provide the Power?

Let’s say you go outside and purchase an electric tankless water heating unit. Well, great. You’ve bought it. Did you research it? Did you see if your actual property is compatible with it?

This happens thousands of times. A buyer purchases an electric tankless water heater but does not bother to check whether their home is compatible. Some homes cannot even provide half the power required to run an electric tankless heater. Some homes simply cannot accommodate an electric tankless water heater on the existing circuits.

Always check the requirements before you buy, and ensure that what you buy you can accommodate.

Do You Know Your Water Pressure?

Do you have the know how to read a pressure gauge correctly? Do you know your water pressure? And is there a pressure release valve installed in your home if your water pressure is over 150 psi?

If not, your home is not compatible with an electric tankless water heater, so do not bother purchasing one.

Most electric tankless water heaters can work in pressure ranges from 30psi-150psi, but usually no higher.

Are You Permitted to Install an Electric Tankless Water Heater?

Do you know that you may need a permit? **

I mean, obviously if you’re renting you should probably contact your landlord. But did you know that you’ll very likely need to get your new electric water heater inspected by an official from your State’s Department of Buildings?

Usually, if you own your property and the land surrounding it, there should be no problem, just some bureaucracy and paper pushing.

** State law varies. For example here in Chicago a new build requires inspection but the anyone replacing an existing heater, on a like-for-like-basis, doesn’t require a building permit.


For your own personal safety, please ensure that if you are not comfortable in carrying out such tasks, or have never done so before, always get a professional to do it for you. It may make your pocket just that little bit lighter, but it might just save you thousands in medical fees, fines and property damage.

Tools You Will Need

These are some of the equipment and supplies you’ll need to have handy, and know how to use correctly, in order to install a tankless electric water heater :

  • A drill and drill bits
  • Phillips screwdriver
  • Flat head screwdriver
  • Pliers
  • Pipe cutter
  • An adjustable wrench
  • Mounting screws and anchors for the new heater (These will be supplied with the unit)
  • Copper or stainless steel flex pipe
  • A Shut off valve
  • A T&P (temperature and pressure) valve
  • Sealing tape
  • Pipe insulation
  • Double pole circuit breakers
  • Grounding wire

Instructions for Tankless Water Heater Installation

OK. If you’re all set and want to give this a go, there’s a step by step guide below that you can follow.

Make sure you have ample time. A skilled tradesman would take 2 or 3 hours to install a tankless water heater in the average home. But for someone who hasn’t done this before, it’s better to allow longer.

We’re going to look at the steps required to safely install the new tankless heater. But first, this video is worth watching. The presenter, Richard Trethewey, is a leading plumbing and heating expert.

How to Install a Tankless Water Heater | Ask This Old House

Seriously folks, I’d like to emphasize how dangerous this task can be if you do not know what you are doing. And again advise that if you are unsure of how to go about such an undertaking safely, please contact and hire a professional who does.

Turn off all circuit breakers.

This step might just save you your life. I think everyone knows that water and live electric cables don’t play well together.

Turn off the water supply.

Seems obvious, right? But you’d be surprised how many people accidentally flood their homes when attempting DIY projects. This step might just save you thousands of dollars in property damage.

Drain and disconnect the old heater.

You’ll need to unscrew the connecting pipes, take out the wiring and remove the old wall mounting brackets.

Take care not to damage the old pipes or wiring,otherwise you’ll have to replace them too and a tough job will have gotten a whole lot tougher.

Remove the front cover.

Take great care in removing the front cover of the new unit that you will install. This can be done with a suitable screwdriver. Remove all of the screws from the front of the unit, and then place them some where that you will not lose them. Every screw is essential for the safe functioning of the water heater.

When removing the cover, do so slowly, as there may be a few cables connected to the main unit, especially if your heater has an LCD screen. Unplug these carefully, and do not apply any more force than feels reasonable. You do not want to break this.

Mount the heater.

Follow the instruction manual to mount the electric tankless water heater to the wall. Ensure this is in a position that will not be covered up by items in storage, and is easily accessible in case of emergencies.

This is usually done with some simple screws and an already supplied mount in the packaging of the heater. This step shouldn’t be too difficult for dexterous folks.

Connect the pipes.

Once the device is mounted, you must now create the hot and cold-water connections that will run in and out of the heater. Usually, these are on the bottom, as most electric tankless water heaters are one way only, and their connections are usually out of the bottom.

For this task, it would be absolutely ideal if you could use a stainless steel flexible pipe that fits your new tankless water heater, as this would accommodate the high temperatures involved without compromising on flexibility and accessibility.

However, if this option is not available to you when installing your heater, it is also possible to use PVC (if it’s suitable and can handle high temperatures) or copper to connect the main water supply to the electric tankless water heater.

In many electric water heaters without a tank, you may find your instruction manual telling you to clean the connections regularly; for this reason, you should ensure to always try and make the connections easily detachable, usually by using a stainless steel flexible pipe.

If, for example, you have used PVC or copper, ensure you take into consideration the quality of your work and smooth of the edges to prevent damage to any threads.

Install flow valve.

When you are going to be conducting repairs or servicing your electric tankless water heater – or just ensuring that all is working correctly, you may want some kind of system that prevents you from having to turn off the water supply all throughout your home.

For this, we recommend you install a valve that allows you to turn off the water flow to the electric heater only, and not to the entire household.

Install pressure valve (if required)

Unless your local plumbing authorities require you do so, there is no need to install a pressure release valve on the “hot water” side of your tankless electric water heater.

However, we strongly recommend that you install a pressure release valve on the cold side of your heating device, to ensure your safety and the safety of your family.

Bleed the hot water system.

Now you should have the unit installed and connected, ready to go. However, ensure you do not yet switch on the cold-water supply, and ensure that mains water is still off. Now, you need to bleed your hot water system.

Go and open all hot water outlets in your home. Bleeding is a process that removes air from your hot water system and prepares the tankless electric heating unit for use. Continue this process for a few minutes, then, switch off all outlets in the house.

Check electrical connections.

Take a good long look at your electrical connections. Are they properly wired? Are they in the correct terminals? Is everything working as it should be? DO NOT SKIP THIS STEP – THIS CAN MAKE THE DIFFERENCE BETWEEN LIFE OR DEATH.

Re-attach cover.

Once you have thoroughly examined your electric tankless water heating unit, re-locate the screws you took from the cover of the unit initially, and carefully re-attach the cover of the heating unit. You are now approaching the completion and finalisation of the installation.

Turn on circuit breakers.

Almost there! Switch on your circuit breakers again, and prepare for action!

Check temperature settings.

Here, you configure the electric heater after it turns on. Be very careful – these are high power machines and setting them to run on their most powerful setting can cause severe burns to any persons who may be unsuspecting.

Test hot water outlets.

Finally, test all your hot water outlets. Run one at a time, and check if the temperature of the water is suitable to your needs. You don’t want everything to be scalding hot, but then you also want your electric tankless water heater to actually heat water to a pleasant level.

Job complete!

And with all that finished, you have successfully installed an electric tankless water heater safely and securely.

To Summarize

Yes, it is possible to do the installation as a DIY project. But 99% of people just won’t have the right tools and knowledge to do it safely. Tankless heaters are great, and they do eliminate the risk of an exploding tank. But they can also present the risk of an electrical fire or severe burns if not fitted in the correct manner.

Ensure that when installing an electric tankless water heater, you refer to and consult your instruction manual at every step of the way.

Failing to do so can be potentially catastrophic both for your health, your property and your bank account. Do not make the mistake that thousands of people do in the USA each year.

Aside from this, an electric tankless water heater is an incredibly efficient device and a great purchase. If set up correctly and configured in a manner that suits your needs, it might just about be the most useful appliance in your household, and a cost effective one, too.

And when buying electric tankless water heaters, ensure that you always check that the heater you are purchasing is compatible with your home.

Some homes are not even capable of providing even half the power required to run one of these machines.


Please ensure that you have a copy of the manufacturer’s manual before beginning the installation process. PDF copies can be downloaded from the links below:

About the author

Steve Bates

Hi, I'm Steve and I currently reside in Chicago, Illinois. Although for most of the last 20 years I was a partner in a HVAC company down in Austin, Texas.

I understand the frustration involved with dealing with water heater repairs and replacing or upgrading to a new, more efficient model.

My aim is offer some basic advice on fixing home hot water systems. And if a repair isn't possible, then to make the process of selecting a new water heater – be it gas or electric - as simple as possible.

So that you can save money and have a safe and reliable hot water system in your home for many years to come.