Using a tankless water heater at home provides a compact and convenient way to heat water.

    Tankless water heaters come in either gas or electric and they can save up to 70 percent on the bill each year. In many cases, tankless water heaters can fit in a garage, basement, attic, or utility closet without taking up too much floor space.

    As long as your local zoning laws do not restrict their installation, you can have a tankless gas water heater installed in your garage, attic, or basement.

    Unlike a storage water heater, which heats the water continuously, a tankless water heater can only heat one volume at a time. Due to this, it may not be an option in households where more than one shower is running at the same time.

    This will depend on the capacity of the unit to supply hot water at one time.

    You can install a tankless water heater as easily as possible by following these guidelines.

    You must make all the necessary preparations before disconnecting and removing the water heater.

    You may need to wait until plumbing, electrical, or vent repairs are complete before you can get hot water again.

    You might need to upgrade your gas meter if you are installing a new gas unit.

    If you have other gas-using appliances in your home, then your meter may not be able to supply the unit. This is because the unit uses a lot of BTUs, so it uses a lot of energy.

    • Ventilation is crucial when installing gas tankless water heaters indoors.
    • You will need to use tightly sealed stainless-steel joints in both the exhaust pipe and the fan of the tankless water heater since the water heater produces a lot of condensation.
    • It must also be connected to a 120-volt circuit, plugged into an outlet/wired directly, and have a gas line.
    • In cold climates, adding a damper will ensure cold air does not return.
    • Depending on the type and model of the heater, you might also need to install a condensate drain, which funnels water from condensation into a drain.
    • To properly drain this waste, you should route it to the floor drain or the utility sink. Read the manufacturer’s documentation regarding venting and plumbing needs.

    An indoor tankless water heater does not need to be vented outdoors. You will need 240-volt electrical power to run it. It can be connected directly to a service panel or to a 240-volt outlet.

    • The codes require that the subpanel is installed next to the unit.
    • Whenever necessary, you can quickly turn off power to the subpanel using its own circuit breakers.
    • Connect the wiring into the subpanel and to the unit.
    • If you’re working on the water heater, you should keep the power off to its circuit at all times.

    Tankless Water Heater Installation 2024

    Depending on your particular water heater, the steps needed to set it up will vary. Be sure to read the instructions completely.

    In addition, improper installation will likely void the manufacturer’s warranty, may cause the system to fail, and will likely lead to serious health problems.

    If you are not a pro at taking care of electrical and plumbing systems, hire someone who is. For a couple of hundred dollars, it’s not worth the risk.

    Additionally, some manufacturers request that their systems are installed by a licensed contractor in order to avoid voiding their warranties.


    Getting Started

    • The first step is to determine the installation location. The location must be compliant with local and state building codes in order to fulfill this purpose.
    • Because your old tank storage water heater already has all the gas and water lines installed, you should install your new tankless water heater behind it.
    • Placement may be affected by factors such as proper ventilation (the vent must be at least 3 feet from the operable window), the location of the water supply to reduce chances of heat loss during traveling, and the location of the electrical panel and plumbing configuration.
    • It is advised that you do not place your heater underneath any air conditioning pipes.
    • Additionally, it shouldn’t be placed over electrical boxes to prevent water from dripping and starting a fire.

    In order to install a tankless heater, you will need the following tools and fixtures:

    It comes with the hardware and instructions you need to install your new tankless heater.

    Upgrade Your Gas Line 

    Since a tankless water heater heats water on demand, it consumes more gas than a storage-tank water heater.

    Some tankless water heaters may consume more gas than the average home furnace.

    The BTU/H requirements for a tank heater may range from 90k to 130k compared to 30k for a tankless water heater. 

    To connect your tankless gas water heater to your gas meter, you’ll need to install a new, larger gas pipe.

    The line size will usually need to be increased from 1/2-inch to 1-inch, in most cases. It’s best to hire a contractor to increase the gas line from your meter.

    Make sure you have enough space before purchasing the heater to determine the right size.

    In the event that an old water heater needs to be replaced;

    • Rinse out the old water heater.
    • Use a heat-resistant hose when draining hot water. Usually, hoses are damaged by the extreme heat contained in hot water tanks. You need to open a hot water faucet to allow the system to drain thoroughly.
    • Unplugging your electric heater is as simple as unplugging your electrical outlet. In the case of gas heaters, it is important to turn off the gas valve first.
    • Once the traditional water heater has been removed from all power and supply lines, discard it.
    • If you are not sure how to dispose of this item properly, contact your local sanitation company or recycling facility.

    Mount the Water Heater

    Follow the manufacturer’s instructions carefully and use the hardware provided. A secure fastening and proper support are important for the unit.

    Install a mounting box made of 2×4 lumber and 3/4-inch plywood four inches away from the wall.

    Ensure that the unit’s weight can be supported by the box. Utilize the right masonry anchors for your foundation wall to hold it to the basement wall.

    It is necessary to directly vent a tankless gas water heater. As a result, they must go directly outside and not go through a chimney.

    As directed by the manufacturer, secure the tankless water heater to the mounting box.

    Installing Water Line and Gas Line

    Instructions for using a gas tankless water heater are provided below. 

    According to the manufacturer’s instructions, install the water heater’s valves.

    Lay copper pipes for hot and cold water lines. Attach water lines to the new heater. You’ll probably have to cut and solder copper piping to the unit.

    Once the water line is connected, run a CSST supply line through the other end, and connect a gas line connector to the existing gas line. Make sure the gas line is still turned off, then connect the CSST line to your tankless water heater.

    Ensure all nuts and gas line connections are tight and turn on the gas. Using a gas sniffer at this point might be beneficial in detecting gas leaks or loose fittings.

    You can test your unit by turning on the pilot light and gas as instructed by your manufacturer and checking for leaks. Heating the water for the first time can take time.

    With electric tankless heaters, you just attach the waterline and plug in a power supply.

    It can run at much higher efficiency and cost less than a traditional heater, so you’re sure to enjoy hot water much more efficiently.

    Install the Pressure Relief Valve

    It is necessary to have a pressure relief valve on a water heater. The safety valve will release if there is too much pressure due to water overheating. Purge valves allow you to maintain the system.

    Following the manufacturer’s instructions, install the pressure relief valve and purge valve

    • Check for leaks by turning on the water supply.
    • Gas the system, bleed the lines if necessary, and inspect for leaks.
    • Once the gas line has been checked for leaks, shut it off until the installation is complete.

    To prevent interruption of the water supply to the rest of your home when performing maintenance on the unit, it is recommended to install a pressure relief valve.

    Install the Exhaust Vent

    It is important to install a tankless water heater according to the manufacturer’s directions.

    Thus, your water heater will run efficiently and effectively, and, most importantly, it will reduce any chance of danger, which would translate into a lower risk of CO2 poisoning.

    In addition to horizontal venting, tankless water heaters can also be vented vertically or through the roof.

    There are basically two ways to install horizontally.

    A downward slope application may require a 90-degree elbow, an adapter for your vent, and a vent hose crafted from stainless steel that has the correct length.

    In this way, the exhaust will be directed away from your house’s walls.

    Lastly, you will finish the vent by attaching a metal or plastic cap to the outside of the vent. After that, you will terminate the installation with a 90° elbow.

    If you choose to install vertically, you simply have to add a vertical condensation trap to your components list in addition to the previously listed components.

    You should be aware of your options before venting a tankless water heater. Here are a few things to consider:

    Non-Direct Vent Fan Assisted

    It can be used to vent horizontally as well as vertically.

    Gases are pushed outside by an electric fan. This pulls oxygen from the interior of the space, which is essential for combustion.

    Fan Assisted Sealed Combustion Direct Vent Indoor

    Also, the venting can be done vertically or horizontally. Directly from the outside, combustion air is brought to the burner.

    The heater is enclosed in an air-tight lid that uses no air from the area where it has been installed.

    It is wired with two piping systems: one for the exhaust and another for the intake of fresh air.


    Combustion air is pulled from the surrounding atmosphere to power outdoor water heaters, then excreted constantly.

    Only warm climates are suitable for this venting method.

    Turn on the Water

    Turn the water heater and pipes to “hot” and open a faucet and shut it off.

    The manufacturer of your new water heater should provide specific instructions for the initial startup.

    An experienced technician is required to handle the replacement of a tankless water heater.

    Do not attempt to solder pipes, connect gas lines, or follow local codes unless you have extensive experience and comfort with these tasks.

    You would need more than one unit for a large home if the hot water takes a while to arrive and the line must be purified after cooling.

    Make your choice after taking into account these factors.

    Frequently Asked Questions

    Do tankless water heaters work for entire houses?

    • The gas-fired tankless units are good for whole-house use, but the electric units are far from adequate.
    • There is a significant energy cost associated with electric units and they’re not Energy Star-rated.

    How long can you run a tankless water heater?

    • Tankless water heaters don’t run continuously as storage tank models do.
    • They only heat water as it is needed. They even have a longer life expectancy than conventional storage tank heaters.
    • Tankless water heaters with gas motors can last for 20 years or more, double the lifespan of tank-type heaters. On average, tankless electric units last between 7 and 10 years.

    Do tankless water heaters need maintenance?

    • A tankless water heater should be regularly maintained twice a year.
    • It is especially important if you live in an area with hard water or you run your water at a high temperature.

    What is the amp draw of an electric tankless water heater?

    • A typical electric tankless water heater requires at least 120 amps of power to operate, whereas a typical household consumes 200 amps.
    • Due to the higher demand for electricity, your electrical system will have to be upgraded.

    How often does a tankless water heater need to be flushed?

    • The tankless water heater needs to be flushed once a year.
    • As a result of the excess magnesium and calcium found in the hard water supply, homeowners with hard water should flush and clean their filters more often, perhaps every six to nine months.

    Why does my tankless hot water heater go cold?

    • This can be caused by an inadequately sized gas line, which results in inconsistent hot and cold water production from your tankless water heater.

    Why does my tankless water heater whistle?

    • If the water heater is whistling, it may be due to a problem with the TPR valve or excess pressure being built up in the tank.
    • The presence of sediment in the drain valve can indicate cracks in the tank. Whistling hot water heaters are dangerous, so you need to turn them off immediately.

    Are tankless water heaters hard to install?

    • Moreover, they require special venting and have larger gas lines due to their higher BTU rating, which makes them more difficult to install.
    • If you have followed the above instructions, you can set it up easily. If you struggle to follow, we recommend you get the help of a professional.

    Can I install an electric tankless water heater myself?

    • In most cases, you can install your own water heater as a homeowner.
    • You still need a permit for the safety inspection in most states, however. The same applies to replacing a water heater.
    David Ra

    From the heart of New York, David Ra brings his expertise to Having studied journalism at NYU, he knows what makes a good story. But here, he's all about the details. David has a special talent: he can take complex products and explain them in a way anyone can understand. When he's not diving deep into product reviews, he's exploring classic books or promoting eco-friendly choices. If you've ever read a review on BestCartReviews and thought, "This makes so much sense!", chances are, David had a hand in it. For clarity and depth, trust David's reviews.

    Leave A Reply