How to Install a Tankless Water Heater

Ever wondered how to up the ante on your home’s energy efficiency? Or maybe you’re simply tired of running out of hot water during your morning shower. Either way, we’ve got an answer for you – a tankless water heater! It’s like having a personal hot spring right in your home. Intrigued? Let’s walk you through the steps on how to install one. 

“A tankless water heater is a smart, energy-efficient upgrade that pays off in both comfort and savings.”

But before you get caught up in the excitement, remember, this isn’t a walk in the park. It’s a bit of a project, requiring some basic plumbing and electrical skills. But hey, we’re here to help you every step of the way.

Things You Need to Know Before Installing Tankless Water Heater

  • Tankless water heaters can be powered by electricity, natural gas, or propane.
  • Installation of a tankless water heater may require upgrading the home’s electrical or gas infrastructure.
  • Installation of a tankless water heater should be done by a licensed professional to ensure safety and proper installation.
  • The installation of a tankless water heater may qualify for federal tax credits or rebates from local utility companies.

Before You Begin: Pre-Installation Preparations

Assessing the Location

Before diving into the installation process, carefully select the optimal location for your tankless water heater. Consider factors such as access to gas or electricity lines, proper ventilation, and proximity to plumbing fixtures.

Gathering Necessary Tools and Materials

To ensure a smooth installation, gather all the required tools and materials beforehand. Common tools include wrenches, pipe cutters, a stud finder, a level, and a power drill. Additionally, you’ll need pipe fittings, venting components, and, of course, your chosen tankless water heater unit.

Step-by-Step Installation Process

1. Turning Off Utilities

Begin by turning off the gas and water supply to your home. Safety is paramount during installation, and shutting off these utilities prevents accidents.

2. Removing the Old Water Heater

If you’re replacing an existing water heater, carefully disconnect and remove it. Drain any remaining water and disconnect gas or electrical connections.

3. Installing Venting

Tankless water heaters require proper ventilation to expel combustion gases. Depending on your unit and local building codes, you might need to install category III stainless steel venting pipes. Ensure the venting system directs gases outside, away from windows and doors.

4. Mounting the Unit

Using a stud finder, locate and mark the studs on the wall where you intend to mount the tankless water heater. Follow the manufacturer’s instructions to securely mount the unit using appropriate brackets. Use a level to ensure the unit is straight.

5. Connecting Water Lines

Attach the water lines to the unit, making sure to follow the proper sequence. Typically, cold water enters from the bottom, and hot water exits from the top. Use pipe fittings and ensure watertight connections.

6. Gas and Electrical Connections

For gas-powered tankless water heaters, connect the gas supply line according to local codes and manufacturer guidelines. If you’re using an electric unit, connect it to the designated electrical circuit following electrical codes. Double-check all connections for accuracy.

7. Testing for Leaks

Before proceeding further, turn on the water and gas/electricity supplies. Check for any leaks around the water and gas connections. Address any leaks promptly to prevent future issues.

8. Flushing the System

New tankless water heaters can accumulate debris during manufacturing and shipping. To prevent clogs and ensure optimal performance, flush the system by running water through it for several minutes. Follow the manufacturer’s recommendations for this process.

9. Setting the Temperature

Most tankless water heaters allow you to set a specific output temperature. Consult the user manual to adjust the temperature to your desired level. Keep in mind that higher temperatures can increase the risk of scalding.

Cost Comparison: Tankless vs. Traditional Water Heaters

When it comes to comparing the costs of tankless water heaters and traditional water heaters, there are several factors to consider. Both upfront costs and long-term expenses need to be factored in to get a comprehensive understanding. 

Type of Water HeaterUpfront CostLong-term Cost
Tankless Water HeaterThese units can be more expensive initially, ranging from $1,000 to $3,000.However, they are energy efficient and can save you up to 20% in water heating bills. Plus, they last about 20 years, almost double that of traditional heaters.
Traditional Water HeaterTraditional water heaters are cheaper upfront, typically costing between $300 and $1,000.But, they can be more expensive in the long-run with higher energy bills and a shorter lifespan of about 10 to 15 years.

So, while tankless water heaters have a higher upfront cost, their long-term savings make them a financially savvy choice for many homeowners. However, every situation is unique and it’s important to consider your personal needs and circumstances. 

Troubleshooting Common Issues with Tankless Water Heaters

Tankless water heaters offer a range of benefits, including energy efficiency, unlimited hot water supply, and reduced space requirements. However, like any household appliance, they can experience issues over time that require proper installation and periodic maintenance. The following steps offer a general guide on how to install a tankless water heater. 

1. Insufficient Hot Water

Possible Causes:

  • Overuse: If multiple fixtures are using hot water simultaneously, the unit may struggle to keep up with demand.
  • Flow Rate: If the water flow rate is too low, the tankless heater might not activate.
  • Mineral Buildup: Accumulated minerals can restrict water flow and affect heating efficiency.


  • Adjust Water Usage: Avoid using too many hot water fixtures at once, especially during peak usage times.
  • Check Flow Rate: Ensure the water flow rate meets the unit’s minimum requirements for activation.
  • Flush the System: Periodically flush the system to remove mineral buildup and improve performance.

2. Fluctuating Water Temperature

Possible Causes:

  • Cold Water Sandwich: Inconsistent water temperatures can occur when the heater briefly shuts off between uses.
  • Temperature Settings: Incorrect temperature settings or fluctuations in incoming water temperature can lead to inconsistent output.


  • Cold Water Sandwich: Some tankless models have features to mitigate this issue, but consider installing a recirculation system for more consistent temperatures.
  • Check Temperature Settings: Verify that the temperature setting on the unit is appropriate for your needs and adjust as necessary.

3. No Hot Water

Possible Causes:

  • Ignition Failure: Gas-powered units may fail to ignite due to issues with the gas supply, pilot light, or ignition system.
  • Electric Malfunction: Electric units might experience problems with the heating element or electrical connections.


  • Check Gas Supply: Ensure the gas supply is connected and the gas valve is open. If using propane, check the tank level.
  • Inspect Pilot Light: If you have a gas unit, make sure the pilot light is lit. Follow the manufacturer’s instructions for relighting if necessary.
  • Electric Troubleshooting: For electric units, check for tripped circuit breakers or blown fuses. Inspect the heating element and connections for damage.

4. Error Codes

Possible Causes:

  • Sensor Issues: Sensors in the unit can detect problems and trigger error codes for safety reasons.
  • Ventilation Problems: Improper venting or blockages can cause error codes related to combustion and exhaust.


  • Refer to Manual: Consult your unit’s manual to identify the specific error code and recommended actions.
  • Inspect Ventilation: Ensure proper ventilation and clear any obstructions from venting pipes.

5. Mineral Buildup and Scaling

Possible Causes:

  • Hard Water: Mineral-rich water can lead to scaling and buildup inside the unit.
  • Lack of Maintenance: Infrequent system flushing and descaling can exacerbate scaling issues.


  • Water Softener: Consider installing a water softener to reduce mineral content in the water.
  • Regular Maintenance: Follow the manufacturer’s guidelines for routine maintenance, including descaling the unit as needed.

6. Strange Noises

Possible Causes:

  • Mineral Deposits: Bubbling or boiling noises can result from mineral buildup in the heat exchanger.
  • Fluctuating Pressure: Rapid changes in water pressure can cause knocking or clicking sounds.


  • Flush the System: Periodically flush the system to remove mineral deposits and improve heat exchanger efficiency.
  • Pressure Regulation: Consider installing a pressure regulator to stabilize water pressure and reduce noise.


Installing a tankless water heater can be a rewarding home improvement project that enhances your comfort while reducing energy expenses. By following the steps outlined in this guide and considering the additional tips provided, you can confidently embark on the installation journey. Remember, whether you’re upgrading to save on utility bills or to enjoy uninterrupted hot water, a properly installed tankless water heater is a valuable addition to any modern home.

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