How to Install or Replace an Electric Tankless Water Heater

A step-by-step guide to installing an electric tankless water heater.

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    In With the New

    Getting a New Electric Tankless Water Heater

    It’s a tankless job but somebody’s gotta do it. 

    All dad jokes aside, installing an electric tankless water heater is an important task that requires careful attention. To make it as easy and painless as possible, we’ve listed step-by-step instructions below.

    Note: Replacing an electric tankless water heater is a complex task that requires high-level technical skills. So if you don’t feel fully prepared with your plumbing and electrical skills, it’s best to hire a licensed professional — in some locations, this is required. And make sure to follow local electrical and plumbing codes for installing and sourcing parts.

    Reliant Plumbing installs tankless water heaters in the AustinDallas, and San Antonio areas. Contact our office to see if we service your area. We also service WestlakeBastropLeander, Cedar Park, and many more.

    reliant plumbing master plumber tankless water heater

    How to Install an Electric Tankless Water Heater

    We understand that installing or replacing tankless water heaters can be very costly. It’s possible to install your own unit, but you should only do this if you are very familiar with working with gas lines, water lines, and electrical. If your tankless water heater is installed improperly, you could be left with extreme damage. Improper gas lines can result in explosions, improper gas venting can result in dangerous carbon dioxide leaking into your home, and poorly installed water lines can leave you with harmful water damage. 

    If you are thinking of a DIY install, it’s important to know the details of your insurance. Some insurance providers will not cover damage to your home unless your tankless water heater was installed by a licensed professional.

    If you are confident in your abilities and have double checked with your insurance, the steps below will walk you through how to install your unit.

    navien tankless water heater

    Installation Steps:

    Step 1 : Read the Product Manual Thoroughly

    Some manufacturers will void the warranty if their systems aren’t installed by licensed contractors.

    Step 2 : Confirm Sizing of Your Electrical Service Panel

    Confirm whether or not your electrical service panel can handle the energy needs of an electric tankless water heater. You might need to upgrade your panel or run a brand new one.

    To find relevant information, you can look at the electrical breaker box or label in your electrical panel. You can also ask an electrician.

    Most sufficient water heaters require a minimum of four 40AMP breakers to supply hot water for a 2 1/2 bath home.

    Step 3 : Be Sure You Have the Right Water Pressure

    If incoming water pressure is above 80 psi, you’ll need to install a pressure reducing valve upstream of the new water heater. If you need to install one, you should do that when installing the cold and hot water connections (see Step 11 : Establish the Water Connections below).

    Step 4 : Pull Permits

    Make sure you pull any required state or city permits for installing or replacing a water heater. 

    Step 5 : Find the Perfect Spot
    • For heating water for the entire home, you’ll want to place the unit closest to where most of the hot water is used.
    • For a point of use system, place these as close to the points of usage as possible.
    • Keep in mind that most electric tankless water heaters have to be installed vertically, with water and power supply connections facing down. 
    • Follow manufacturer’s directions on leaving at least a certain minimum clearance for servicing.
    • Overall, you want to avoid areas where: 
      • Freezing temps can affect the unit.
      • Any type of liquid could regularly splash on the unit.
      • There’s a lot of humidity and moisture.
    Step 6 : Turn Off Circuit Breakers

    Turn off all circuit breakers related to the new unit. This is very important!

    Step 7 : Turn off the Main Water Supply

    You don’t want to flood your workspace!

    Step 8 : If Needed, Disconnect Your Existing Water Heater
    • Turn off the water supply to the unit. 
      • If there’s no shut off valve before the heater, turn off your main water supply.
      • Shut off any power and gas supply valves feeding the heater.
      • Drain the unit. 
        • For hot water, use a hose rated to withstand heat. Open a hot water faucet to release pressure in the system. Let it fully drain. 
    • Disconnect the water heater from the gas and water lines. 
    • Dispose of your old water heater properly. 
      • Contact your local recycling and/or sanitation departments for information on how to properly get rid of it.
    Step 9 : Take Off the Cover
    • Remove any screws that are securing the front cover of the new unit. 
    • Important: You might have to remove at least one plug before you can put it aside.
    Step 10 : Mount the Unit to the Wall

    Its package should include the appropriate anchors and screws. 

    Step 11 : Establish the Water Connections
    • Establish the cold and hot water connections. Cold is usually on the right side.
      • The easiest route is using stainless steel flex pipe with Teflon tape.
      • You can also use copper tubing that’s rated for high temperature applications. 
      • If you need to cut into a pipe, clean up the edges. 
      • When you solder pipes, flush them before connecting them to the water heater. And remember that excess heat can damage the water heater.
      • It’s a good idea to install a shut-off valve before and after the heater, to turn off the water supply to the unit for maintenance without shutting off the supply to the rest of your home.
      • If you need to install a pressure reduction valve, you should do so now on the cold water side. 
      • You probably won’t need to install a temperature and pressure relief valve (T&P). But, you should confirm whether or not you need one, by checking your local and state installation codes.
    Step 12: Purge Air & Check For Leaks
    • Purge air from the unit and the pipes by opening several hot water outlets. 
    • While waiting, you should check every connection for any leaks.
    Step 13 : Close the Water Outlets

    Do not skip this step!

    Step 14 : Create the Electrical Connections
    • The heater should be on one side and the electrical panel on the other. 
    • Follow the manufacturer’s wiring diagram, and their directions for choosing the correct wire, circuit breaker number, and circuit breaker size. 
    • After cutting every wire set to length and stripping it, push them through the bottom holes of the new water heater’s housing.
    • Then secure the wires to the right slots on the terminal block.
      • Refer to the product manual for optimal torque.
      • Remember that for each circuit, a ground conductor needs to be connected to the circuit breaker panel and the unit’s grounding busbar.
    • Check all of the electrical connections, to confirm that you placed all the wire sets correctly.
    Step 15 : Put the Cover Back On

    Use the screws you removed earlier.

    Step 16 : Turn on the Circuit Breakers

    Now, the unit should be on. Choose your preferred unit settings.

    Step 17 : Check the Water Temperature

    Turn on the hot side of a faucet in your home. Check the water temperature after it has stabilized. If you want to adjust the temperature, adjust it on the unit.

    Avoid Disaster

    Take Action Today to Protect Your Home

    Act quickly to address minor plumbing issues before they turn into expensive disasters. Our expert services can help protect your home from damage, giving you peace of mind and saving you money in the long run.

    two commercial tankless water heaters

    Additional Resources

    LEARN MORE ABOUT TANKLESS WATER HEATERS

    Cost to Install or Replace Tankless Water Heaters

    Our master plumbers put together this page to help you understand the costs involved if you hire a licensed plumber for your project.

    Preventative Maintenance for Your Tankless Heater

    Tankless water heaters are known for their longer lifetimes. They can outlast a conventional tank style water heater by more than 10 years if they are properly maintained.

    Tankless Water Heater Sizing Guide

    Unlike a tank style water heater that is limited by how much water it can store in its tank, tankless water heaters are limited by their flow rate.

    Best Brands of Tankless Water Heaters

    We understand that the options available in tankless water heaters can be overwhelming. There are so many brands to choose from, so we sat down with our Master Plumbers to get their opinions.

    Common Tankless Water Heaters Issues & How to Fix Them

    Learn about the most common problems we hear about with tankless water heaters, how to diagnose them, and most importantly, how to fix them.

    Is it Time to Replace Your Hot Water Heater?

    Your hot water heater is one of your hardest working appliances and it’s best to replace it before it stops functioning.