Maximize Energy Efficiency: Installing A Tankless Water Heater In Your House

Whether you’re tired of running out of hot water or simply looking to upgrade your home’s water heating system, installing a tankless water heater is a smart choice.

In this guide, we’ll provide you with step-by-step instructions, expert tips, and all the information you need to successfully install a tankless water heater in your home.

Say goodbye to bulky tanks and hello to endless hot water as we walk you through the process from start to finish.

Navien tankless water heater
(photo: navien)

Installing A Tankless Water Heater Can Be Challenging

Note that the professional installation by the qualified and licensed technician is recommended, ensuring compliance with local plumbing, venting, gas, and electrical codes.

However, if you prefer a DIY approach, you can use the manufacturer’s guide along with our instructions as a reference. We provide valuable information, tips, and tricks to support your tankless water heater installation.

There are many manufacturers of tankless water heaters; Rheem, AO Smith, Titan, or Japanese Rinnai, Noritz, Takagi, or European Bosch, Stiebel Eltron, using gas and electricity, which are more or less complicated to install.

Electric units are generally simpler to install, as they don’t require venting. However, they may require a new electric panel and higher voltage power supply.

Gas tankless water heater installation involves mounting the unit, connecting electricity, gas, and water lines, and installing a flue for venting.

It’s important to note that installing a tankless water heater can be challenging and potentially hazardous if not done correctly. Most on-demand models can be installed almost anywhere, providing flexibility in terms of placement. They can be placed indoors or outdoors, in the garage, attic, bathroom, kitchen, or any suitable location that maximizes comfort and water heating experience.

Unlike conventional tank-type models, tankless water heaters eliminate the need for a designated room, freeing up valuable space in your home. Their small and compact design allows for easy wall mounting, while features like sealed combustion chambers and direct venting ensure safe indoor installation and usage.

Installing a Tankless Water Heater – Things to Consider

Tankless models are small, elegantly designed, and offer flexible installation options, including both indoor and outdoor mounting. It’s important to note that each water heater installation is unique and specific to the home and its specific requirements.

Skills needed when installing a tankless water heater:

  • Handling power tools
  • Working with flaming torches
  • Working with gas
  • Soldering copper pipes
  • Working with plumbing systems
  • Working with electric systems

What to consider when installing a tankless water heater:

Choosing A Location

The ideal location for your water heater depends on various factors, including the type of water heater selected, your personal preference, the size and design of your home, and available installation or mounting spaces. It is generally recommended to install the unit close to the point of use, such as the bathroom, laundry room, or kitchen sink, for convenient access and safe operation.

To ensure the security of your home, it is important to choose a location where potential water leakage will not cause damage, particularly when considering an attic installation. Installing a suitable drain pan beneath the tankless water heater can help mitigate the risk of water leaks.

If you plan to install the unit in the attic, it’s important to consider factors like heat buildup or freezing temperatures that may impact its normal operation, as modern tankless units often incorporate delicate electronics.

Remember to adhere to the recommended clearances to allow for unobstructed, efficient, and safe operation of the tankless water heater.

Wall Installation

Ensure the secure attachment of the heater to the wall by using the recommended number of bolts. Utilize an installation bracket and align the upper and bottom holes to vertically mount the unit, unless specified otherwise.

If the wall lacks sufficient strength to support the weight of the heater, reinforcement is necessary. It is advisable to fasten the tankless unit to the wall studs or use an additional piece of wood placed between the wall studs for added stability.

Providing The Electric Power Outlet

When installing a tankless water heater, it is crucial to adhere to local and national electrical codes. This is particularly important as tankless units require a higher voltage power supply, typically 120-240 VAC, 60Hz, with sufficient amperage and proper grounding of the wall outlet. It is essential to verify that the voltage of the tankless water heater matches the rating plate to ensure safe and proper operation.

Connecting The Heater To The Gas Line And/Or Gas Line Upgrade

  • Ensure that your tankless water heater is compatible with the specific gas type intended for use. Verify the inlet gas pressure to ensure it falls within the range specified on the rating plate. Note that your tankless unit cannot utilize natural gas and propane interchangeably without modifications (conversion kit).
  • Propane water heaters should not be installed below grade, such as in a basement.
  • Install a manual gas control valve in the gas supply line, positioned near your water heater. Additionally, it is important to inspect all connections for potential gas leaks using a soap-water solution.
  • The gas supply line should be appropriately sized based on the gas type, gas pressure, and other relevant factors to ensure proper gas flow.
  • To prevent sediment from entering the gas line, it is recommended to incorporate a sediment trap at the bottom of the gas line.

Plumbing Changes Or Upgrades To Provide Hot And Cold Water To The New Unit

  • Ensure that only potable water, free from dirt and other contaminants, is used with your tankless water heater.
  • Use pipes that are at least the same diameter as the connections of the water heater. It is recommended to install unions and flexible copper connections, which allow for easy disconnection during maintenance and repairs.
  • During new installations, take care to avoid reversing the hot and cold water lines.
  • Properly insulate both the hot and cold water lines to conserve water and energy. Also, protect the water heater and pipelines from freezing temperatures.
  • Install a manual shut-off valve on the water supply line before connecting it to your tankless water heater. Additionally, consider installing one on the hot water side as well.
  • Ensure the installation of a pressure relief valve.
  • Verify that the water supply has sufficient pressure and that all connections are tight, with no signs of leaks.


Venting is a crucial step in the installation of a tankless water heater. It plays a vital role in ensuring the safe operation of the unit. Improperly installed venting systems can result in obstructed pathways, which can cause dangerous gases like carbon monoxide to leak into the living space.

Following the recommendations and codes for venting during the installation of a tankless water heater is essential for safe operation and your peace of mind.

Tankless water heaters with concentric venting systems and sealed combustion, such as direct vent models, allow for flexible and simpler installation with zero clearances required for wall or roof penetration.

In indoor installations that utilize a single vent system and concentric vent pipe, a metal pipe is used for exhaust gases, while PVC or metal is used for fresh air intake. If the water heater uses indoor air for combustion and is installed in a confined space, specific provisions or two permanent openings must be provided.

It is important to use approved venting materials and ensure that every connection is accessible for inspection, cleaning, and replacement. Proper installation of a condensation collar or trap is also necessary.

Venting should be as direct as possible, minimizing the length and number of elbows. For horizontal venting, support is required at specified intervals (as per manufacturer’s instructions) to avoid dips and sags. Vertical runs should include a condensate drain and vertical terminations with a rain cap. Refer to the manufacturer’s guide for maximum lengths and additional instructions.

Exterior models of tankless water heaters are ventless and typically installed outside, often within a recessed enclosure for protection against the elements.

Installing Devices To Enhance The Performance Of A Water Heater

  • Water softener installation is essential in areas where hard water is a problem. Sediment build-up in water heaters can lead to reduced effectiveness and performance.
  • It is recommended to install a temperature controller, which allows for temperature control, monitoring, and error code display (check out these Rinnai error codes, as an example).
  • To prevent scalding, the installation of a tempering or mixing valve is advised. This valve helps limit the temperature of hot water to a safe level.
  • On closed-loop systems, it is important to install an adequately sized thermal expansion tank. This tank helps protect the water heater from excessive pressure and repeated relief valve operation.
  • If the pressure relief valve is not factory-installed, it is required by the ANSI CSA standard for all water heating systems. It should be rated up to 150 psi and allow for the maximum BTU/hr gas input.
  • Electric tankless water heaters are generally less complex to install and involve fewer considerations. However, it is important to ensure that the minimum supply pipe diameter is met.

Summary Of Installation Requirements

  • All local and national codes should be met to ensure compliance.
  • Proper installation of the unit is crucial for safe and effective operation, encompassing electrical, gas, and water connections.
  • Gas pressure adjustments were not required as it was set correctly at the factory.
  • Adequate space must be provided for the installation, service, and maintenance of the unit.
  • Ensure that the units are installed in areas where there is sufficient air available for proper combustion.
  • The vent termination should meet the requirements in terms of noise, clearance, and air quality.
  • Follow the instructions for venting, including the appropriate materials, sizes, and lengths.

As demonstrated in the above guide, installing a tankless water heater should not be challenging as long as the provided directions are followed. However, it is advisable to seek assistance from a licensed technician.

Failure to install the tankless water heater correctly results in improper and unsafe operation, shorter unit life, and possible warranty cancellation.


Can I Install A Tankless Water Heater Myself?

Yes, you can.
If you are comfortable with DIY projects and have experience with plumbing and electrical work, you may choose to install the tankless water heater yourself. In such cases, it is crucial to carefully read and follow the manufacturer’s installation instructions and consult any applicable local codes or regulations. It is also recommended to gather the necessary tools and materials before starting the installation process.
It is worth mentioning that many manufacturers require professional installation for the warranty coverage to be valid.

Can I Install A Tankless Water Heater In Any Location Of My Home?

Tankless water heaters can be installed in various locations within your home, including indoors, outdoors (with suitable models), attics, and near the point of use.
The specific installation location depends on factors such as the model, fuel type, and local building codes. Indoor installations are common and require proper ventilation and access to utilities.
Outdoor installations require weather-resistant housing and protection from the elements. Attic installations require consideration of factors like heat buildup and ventilation. Point-of-use installations provide hot water quickly to specific fixtures.
Always refer to manufacturer guidelines, local codes, and consider safety when choosing the installation location.

Do I Need Isolation (Service) Valves?

It is generally recommended to have service valves installed when installing a tankless water heater.
Service valves, also known as isolation valves or shut-off valves, provide a convenient way to shut off the water supply to the water heater for maintenance, repairs, or replacement without affecting the water supply to the rest of the house. They allow you to isolate the tankless water heater without needing to shut off the water to the entire building.
Service valves make future servicing or troubleshooting easier and can help prevent water leakage during maintenance. Therefore, including service valves in the installation of a tankless water heater is a wise choice.

Related Articles

Similar Posts