Essential Guide to Installing a Tankless Water Heater at Home

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 hook up a tankless water heater.

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

Overcoming the Challenges of Installing a Tankless Water Heater

Installing a tankless water heater can be challenging, and professional work by a qualified, licensed technician is strongly recommended. This ensures compliance with local plumbing codes, venting, gas, and electrical codes and guarantees safe and efficient operation.

If you prefer a DIY approach, use the manufacturer’s guide along with our detailed instructions. We provide valuable tips and insights to support your tankless water heater installation process.

There are many manufacturers of tankless water heaters, including Rheem, AO Smith, Titan, Rinnai, Noritz, Takagi, Bosch, and Stiebel Eltron. These models, available in gas and electric versions, vary in complexity when it comes to installation.

• Electric Units: These are generally easier to install since they don’t require venting. However, they may necessitate a new electric panel and higher voltage power supply.
• Gas Units: Installing a gas unit involves mounting the unit, connecting electricity, gas, and water lines, and a venting system.

Installing a tankless water heater can be challenging and hazardous if done incorrectly. However, most on-demand models offer flexibility in placement, as they can be mounted indoors or outdoors—in the garage, attic, bathroom, kitchen, or any other suitable location to enhance your comfort and water heating experience.

Unlike conventional tank-type models, tankless water heaters free up valuable space with their compact design and the wall mount. Features like sealed combustion chambers and direct venting ensure safe and efficient indoor usage.

Tankless Water Heater Installation: 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:

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

Required Tools

• Adjustable wrenches
• Pipe wrench
• Screwdrivers
• Wire cutters
• Hacksaw
• Reciprocating saw
• Drill
• Propane torch
• Level
• Teflon tape

Choosing a Location

Selecting the ideal location for your tankless water heater requires careful consideration of several factors. These include the type of water heater, the size and design of your home, your personal preferences, and the available installation or mounting spaces.

Key Considerations:

1. Proximity to Point of Use
   Install the unit close to high-demand areas like bathrooms, kitchens, or laundry rooms for convenient access and efficient operation.
2. Safety and Water Damage Prevention
   • Choose a location where potential water leaks won’t cause significant damage.
   • If mounting in an attic, use a suitable drain pan to mitigate the risk of leaks.
3. Environmental Factors
   • Avoid areas with extreme temperatures, such as attics prone to heat buildup or freezing conditions, as these can affect the unit’s performance.
   • For outdoor models, use them in mild climates, preferably in a recessed box, to protect against harsh weather.
4. Clearances and Maintenance
   • Follow the manufacturer’s recommended clearances to ensure proper ventilation, efficient operation, and easy access for maintenance.
   • Provide sufficient space around the unit for future service needs.
5. Air Quality and Safety
   • Avoid placing the water heater in rooms with chemicals, gasoline, or flammable vapors.
   • Steer clear of locations with excessive dirt, dust, or aerosols, which can clog vents, reduce fan efficiency, and damage the unit.
6. Special Considerations
   • If your area has hard water, use a water softener to prevent frequent flushing and buildup.
   • For high-altitude options, consult the manufacturer to confirm compatibility.
   • Only install the unit in mobile or manufactured homes if it is certified for such use.

Locations to Avoid:

• Attics, due to safety concerns and environmental risks.
• Enclosed spaces with poor air quality or limited ventilation.

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.

Electrical Requirements for Installation

Proper adherence to electrical standards is critical. These units often require a higher voltage power supply and precise grounding to ensure safe and reliable operation.

Key Considerations:

1. Compliance with Codes
   • Always follow local and national electrical codes during installation.
   • Verify that the voltage matches the rating plate on the water heater to avoid operational issues or hazards.
2. Power Supply
   • Tankless water heaters typically require 120-240 VAC, 60 Hz, with sufficient amperage.
   • Ensure the wall outlet is properly grounded.
3. Grounding and Protection
   • Ground the tankless water heater in compliance with electrical codes to prevent potential electrical faults.
   • Most tankless units come equipped with freeze protection systems that require continuous electrical power to operate.
4. Manufacturer’s Specifications
   • Review the manufacturer’s instructions for specific electrical requirements. For example, Rinnai models in the U.S. and Canada require 120 VAC and 60 Hz from a properly grounded circuit.
5. Optional Accessories
   • Install a remote control if one is not provided with the unit to enhance convenience and usability.

Connecting to the Gas Line

When installing a tankless water heater, either Noritz, Rinnai, Takagi or any other brand, see the model description on the rating plate and read the manufacturer’s instruction before any work. The rating plate carries information such as the gas type, electric rating, gas and water pressure.

• 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 Work

• 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 use 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 puttin 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 Requirements for Installation

Proper venting is a critical part of installing a tankless water heater. It ensures safe operation by directing harmful gases, like carbon monoxide, out of your living space. Improper venting can lead to dangerous gas leaks, so following recommended guidelines is essential.

Key Considerations:

1. Venting Guidelines and Codes
   • Always adhere to the manufacturer’s recommendations and local codes for venting to ensure safety and compliance.
   • Use only approved venting materials and ensure all connections are accessible for inspection, cleaning, and replacement.
2. Types of Venting Systems
   • Concentric Venting Systems: Direct vent models with sealed combustion provide a flexible and simple installation process, requiring zero clearance for wall or roof penetration.
   • Single Vent Systems: For indoor units, a metal pipe is used for exhaust gases, while PVC or metal handles fresh air intake. If the unit uses indoor air for combustion and is in a confined space, provide two permanent openings for adequate airflow.
   • Exterior Models: Outdoor water heaters are ventless and typically located in recessed enclosures to protect against the elements.
3. Best Practices
   • Position the water heater as close as possible to the vent area to minimize venting length.
   • Keep venting runs as direct as possible, reducing the number of elbows to improve efficiency.
   • For horizontal venting, support the pipe at specified intervals to prevent dips and sags.
   • Vertical vent runs must include a condensate drain and a rain cap to prevent water entry.
4. Safety Measures
   • Ensure the vent system is sealed airtight to prevent leaks.
   • The vent pipe must be dedicated to the water heater and easily removable for maintenance.
   • Avoid blocking the vent termination. Exhaust vents should not point toward windows, doors, or air intake devices.
5. Fresh Air and Clearance Requirements
   • Ensure the water heater has sufficient fresh air for proper combustion and ventilation of flue gases.
   • Use the recommended vent size and materials, maintaining consistent diameter without modifications.
   • Leave adequate space around the unit for servicing and ensure proper clearances from nearby objects.

Installing Devices to Enhance The Performance of a Water Heater

• Using water softener in areas where hard water is a problem is essential. 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, using the 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-provided, 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.

Step-by-Step Installation Guide

1. Turn Off Supplies
   • Shut off the water, electricity, and gas supply to the old water heater.
2. Drain and Disconnect
   • Drain the old unit and disconnect all existing connections.
3. Prepare New Supply Lines
   • If necessary, install new supply lines for gas and water, using either solid or flexible piping as appropriate.
4. Mount the Tankless Water Heater
   • Mount the unit to the wall using existing wall studs or a newly built frame made from 2 x 4″ lumber.
   • If the heater includes a mounting bracket, use it for easier installation.
   • Ensure the bracket is level using a leveling tool.
   • Secure the bracket to the wall with four screws, hang the heater on it, and fasten the top and bottom of the heater to the wall.
5. Connect the Gas Line
   • Attach a shut-off valve and sediment trap to the gas line before connecting it to the heater.
   • Bleed the gas line to ensure no air is trapped.
6. Connect the Water Line
   • Attach the water line to the heater, using Teflon tape to ensure a secure and leak-proof connection.
7. Connect Electrical Wiring
   • Wire the unit according to the manufacturer’s instructions, ensuring proper connections for electricity, gas, and water.
8. Check for Leaks
   • Inspect all connections for leaks before proceeding.
9. Install the Vent
   • Follow the manufacturer’s instructions to install the vent system.
   • Use a reciprocating saw and the provided template to cut a vent hole in the drywall, ensuring proper placement.
10. Turn On Supplies
    • Restore electricity, gas, and water supplies.
11. Start the Water Heater
    • Power up the water heater and test for proper operation.

Important Note: All the work must be performed by a licensed professional to maintain the validity of the warranty and ensure safety.

How to Activate a Tankless Water Heater

Activating a tankless water heater involves several automated steps that ensure efficient and safe operation. Here’s how the process works:

1. Opening the Hot Water Tap
   • Turn on a hot water tap to initiate the system. A minimum water flow, as specified by the manufacturer, is required to activate the unit.
2. Flow Detection
   • The flow sensor detects proper water flow and signals the system to begin operation.
3. Fan Activation
   • The fan activates to prepare for combustion and venting.
4. System Check
   • The computer performs a diagnostic check. If no issues are detected, it signals the igniter to generate sparks.
5. Ignition
   • The igniter generates sparks, accompanied by a buzzing sound, indicating that ignition is in progress.
6. Gas Burner Activation
   • The main gas valve opens, and the burner lights up to heat the water.
7. Water Heating
   • Cold water flows through the heat exchanger and heats up to the set temperature. The gas valve modulates power and temperature based on hot water demand.
8. System Shutdown
   • When the water flow drops below the deactivation point, the heater automatically shuts down.

Maintenance and Installation Tips

Perform regular maintenance as outlined in the manufacturer’s instructions, including cleaning, visual inspections, and small replacements, to extend the heater’s lifespan and maintain efficiency.

Ensure professional installation to guarantee safe operation, reliable performance, and warranty compliance.

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 located 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.

FAQ