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Electric Water Heater Installation: Step-By-Step Guide

Note: This post may contain affiliate links. This means that at no cost to you, we may receive a small commission for made purchases.

Buying a new electric water heater can be an exciting time. Soon you will be free from the troubles of your last one, and you’ll have hot water on demand without much issue.

But if there’s one thing that anybody who has installed a brand-new electric water heater knows, it’s that the process can be difficult as it involves switching a few pipes and electrical wires around.

If you’re planning on installing your water heater yourself, you might be wondering how to go about doing so.

This article is going to walk you through all the steps involved in installing a new electric water heater.

We’ve broken this down for you with a step-by-step guide on how to install an instant (tankless) water heater.

How To Install An Instant Water Heater

Electric Water Heater Installation

What Is An Instant Water Heater?

An instant water heater is an alternative to a classic tank water heater. The main difference is that they don’t store hot water for future use, they instead create it as and when you decide.

There are a few benefits to choosing an instant water heater over a classic tank including energy conservation, space, and cleanliness.

Can I Install An Instant Water Heater Myself?

Instant water heaters have fewer components than tank water heaters, so it’s certainly possible to do this.

In some ways, because of how much smaller the unit is likely to be, it’s going to be even easier to install a tankless water heater.

However, it does require some DIY knowledge and some planning time, and there are sections that you may need professional help with (see steps 3 and 4).

Below, we’re going to show you step by step how to install an instant water heater.

Step 1: Disconnect Your Old Water Heater

Whether you’re swapping an old tank water heater, or upgrading your instant heater to a new model, the first thing you’re going to need to do is to disconnect from the old one.

First, you need to make sure that you stop the flow of water by closing both valves on your old heater, then you need to make sure you drain as much water as you can by connecting a hose to the bottom of your tank.

Step 2: Mount Your New Water Heater

Instant water heaters (see also ‘Hot Water Heater Vent Pipe Size‘) are usually mounted on a wall and are usually connected directly to a vent. What this means is that they have to be connected to the outside directly.

Venting your new water heater is an integral part of the process that you need to take seriously.

There are different types of vents available, such as ductless mini-splits and traditional vented systems. Each type of vent has its own unique requirements.

You’ll also need a good seal between your water heater and the exterior. This should be made by caulking any gaps or cracks that exist.

Notice the vent connected to the top of these large heaters in the image above. You should always ensure that all vents are closed before installing any equipment. This will prevent moisture from getting into the system.

There are a few ways to mount your new water heater (see thermostat), but generally, we would suggest simply bolting your new unit to the wall.

Check your water heater – does it have spaces for screws? Or did it come with a full set already? Either way, you’ll need to find a way to attach it securely to the wall.

The image above shows a typical internal and external diagram of a tankless electric water heater.

Notice the mounting screws will usually be on both sides of the tank, so you’ll need to make use of an electric drill to bore holes into your wall if you don’t already have them.

Step 3: Connect Your Piping

Once your water heater has been attached to the wall, you’ll need to connect your piping to it as well.

You’ll probably need to run at least two lines: one line to supply cold water (which will go through your faucet) and another line to provide hot water (which will go to your shower).

These are often highlighted in red or blue, either in the color of the piping, or else a tag that will indicate the color to you. You can see an example of this in the image below.

The best way to determine where to start running your piping is to look at your existing plumbing (see also ‘3 Main Types Of Plumbing Cleanouts You Should Know‘).

As long as there isn’t too much damage, you can just follow what was there before. For example, if you had a bathroom sink in your kitchen, you could just continue down there.

If you’re unsure about which direction to run your piping, you may want to consider having a professional plumber help you out. They’ll know exactly where everything goes and what needs to be done.

Step 4: Connect Electrical Wires

Installing an instant water heater requires electrical wiring. The most common type of wire used for this purpose is called “EPDM” (ethylene propylene diene monomer).

EPDM is a flexible material that allows you to bend it around corners without breaking.

While you don’t necessarily need to have electrical wires professionally installed, it’s still recommended that you hire someone who knows what they’re doing.

Installing electrical wires incorrectly can cause serious problems like electrocution or fire.

Step 5: Test The System

After you’ve finished installing your piping, you’ll probably want to test your entire system to see if it works properly. You can do this by turning off your main valve and opening up each individual fixture.

Make sure that the water coming out of them flows normally. If it doesn’t, you might have a problem somewhere along the line.

Many modern electric water heaters have an interactive panel that you can use to set up personalized presets and manually control water temperature.

Check the manual of your water heater for specific advice on how to make these adjustments.

Step 6:Turn On Your Hot And Cold Water Fixtures

Now that you’ve tested your system, you can turn on your hot and cold water fixtures. You should notice that your water starts flowing immediately. Congratulations! You now have a working instant water heater.

Final Thoughts

The main thing to keep in mind when installing an instant water heater is that you need to carefully consider each step of the process.

When it comes to swapping piping and electrical wires, you’ll need to make sure you know exactly what to do before changing them, as these can be dangerous.

However, all other steps are completely possible for you to do on your own. An instant water heater (see also ‘Water Heater Dimensions‘) can be an incredible addition to your home and we hope that you get yours working soon!

Best of luck in your DIY adventure!

author avatar
Anthony Barnes
Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age


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