Installing a tankless water heater is an excellent way to enhance your home's energy efficiency while ensuring a constant supply of hot water. However, the installation process requires precision and attention to detail. A mistake during the installation can not only cause inefficiencies but may also lead to safety hazards and costly repairs down the line. Below are the most common mistakes to avoid during the installation of a tankless water heater, along with practical tips on how to prevent them.

  1. Incorrect Sizing of the Unit

One of the most critical factors in the successful installation of a tankless water heater is choosing the right size unit for your needs. A common mistake is either overestimating or underestimating the required flow rate and temperature rise, which directly impacts the unit's performance.

Why It's a Mistake:

  • Under-sizing can result in insufficient hot water supply, especially in households with high hot water demand.
  • Over-sizing may lead to unnecessary energy consumption, reducing the overall efficiency of the system and increasing installation costs.

How to Avoid It:

  • Accurately calculate your home's hot water demand by considering factors such as the number of bathrooms, the types of appliances, and the number of people in the household.
  • Use the manufacturer's sizing guide to choose the appropriate unit based on the expected flow rate (measured in gallons per minute or GPM) and the desired temperature rise (the difference between the incoming cold water temperature and the desired hot water temperature).
  1. Failure to Properly Vent Gas Units

Gas-powered tankless water heaters require proper venting to expel exhaust gases safely, including carbon monoxide. A common mistake during installation is improper venting or failure to install the venting system according to local codes and manufacturer guidelines.

Why It's a Mistake:

  • Improper venting can cause dangerous gases to accumulate in your home, which can pose serious health and fire risks.
  • Inadequate venting may also cause the system to overheat, leading to system malfunctions and even unit failure.

How to Avoid It:

  • Always follow the manufacturer's instructions for venting, including the correct vent size, venting materials, and placement of vent pipes.
  • Ensure that the vent system is properly sealed and that no exhaust gases are leaking into the living space.
  • If you are unsure about venting requirements, consult a professional plumber or HVAC technician to ensure compliance with local building codes.
  1. Improper Gas Line Installation (For Gas Units)

Gas-powered tankless water heaters require a properly sized gas line to function correctly. A common mistake is using an undersized gas line, which can restrict the flow of gas and prevent the unit from operating efficiently or safely.

Why It's a Mistake:

  • Using an undersized gas line can cause the water heater to fail to ignite or operate at reduced capacity, leading to inconsistent hot water and increased wear on the unit.
  • In extreme cases, improper gas line installation can cause gas leaks, which can be hazardous.

How to Avoid It:

  • Verify that the existing gas line is large enough to support the new water heater. You may need to upgrade the gas line if the existing one is too small.
  • Use the sizing chart provided by the manufacturer to determine the correct pipe size and ensure the gas pressure is within the specified range.
  • Consider hiring a licensed gas technician to inspect or install the gas line to ensure safety and compliance with regulations.
  1. Neglecting Electrical Capacity for Electric Units

Electric tankless water heaters require a substantial amount of power to operate efficiently. One of the most common mistakes is neglecting to check the electrical capacity of your home before installation.

Why It's a Mistake:

  • Electric water heaters draw a large amount of current, and if your home's electrical panel cannot support the additional load, it could cause frequent circuit breaker trips or even electrical fires.
  • Overloading the system can damage the water heater and other electrical appliances.

How to Avoid It:

  • Before installation, ensure that your electrical panel has enough capacity to handle the additional load. Most electric tankless units require a dedicated circuit with a rating of 100 to 200 amps.
  • Check the manufacturer's specifications to determine the required amperage for your specific model and compare this to your home's current electrical setup.
  • If necessary, consult an electrician to upgrade your panel or install a new dedicated circuit for the water heater.
  1. Poor Placement of the Unit

The placement of your tankless water heater is crucial for both functionality and safety. A common mistake is installing the unit in an inappropriate location, which can affect the unit's performance and access for future maintenance.

Why It's a Mistake:

  • Improper placement can restrict airflow or obstruct essential connections like the water and gas lines.
  • Installing the unit too far from the point of use can result in long wait times for hot water, reducing the efficiency of the system.

How to Avoid It:

  • Follow the manufacturer's recommendations for the required clearance around the unit, ensuring that it has adequate ventilation and room for maintenance.
  • For gas-powered units, ensure that the location allows for proper venting and access to an exterior wall.
  • Position the unit as close to the point of use as possible to minimize heat loss and improve the time it takes for hot water to reach faucets.
  1. Ignoring the Need for a Pressure Relief Valve

A pressure relief valve is a critical safety feature that helps protect the unit from excessive pressure buildup. Forgetting to install or incorrectly installing this valve is a common mistake.

Why It's a Mistake:

  • Without a properly installed pressure relief valve, excessive pressure could cause damage to the water heater or even lead to dangerous situations such as an explosion.
  • A malfunctioning valve can also affect the unit's overall efficiency.

How to Avoid It:

  • Always install the pressure relief valve according to the manufacturer's instructions and local building codes.
  • Ensure that the valve is connected to a proper discharge location that safely directs excess water away from the unit.
  • Test the valve periodically to ensure it is working correctly.
  1. Not Testing for Leaks and System Integrity

After installation, many people fail to thoroughly check for leaks or ensure that all connections are secure. This is a critical oversight that can result in water damage or the malfunctioning of the system.

Why It's a Mistake:

  • Leaking water can cause significant damage to your home, and failing to detect leaks early can lead to costly repairs.
  • Gas leaks can pose a serious safety risk, including the potential for fire or explosion.

How to Avoid It:

  • After making the necessary connections, test for leaks by turning on the water supply and checking all water and gas lines for leaks.
  • Use soapy water on gas connections and watch for bubbles, which will indicate a leak.
  • Make sure to test both hot and cold water lines and ensure that no water is leaking from the unit itself or from any of the plumbing connections.
  1. Skipping Regular Maintenance

Even after installation, regular maintenance is key to ensuring your tankless water heater operates efficiently and lasts for many years. Neglecting maintenance can lead to mineral buildup, reduced efficiency, and potential failure.

Why It's a Mistake:

  • Hard water buildup can clog the system and reduce its performance.
  • Lack of regular maintenance can lead to costly repairs and premature system failure.

How to Avoid It:

  • Schedule annual descaling of your unit, especially if you live in an area with hard water.
  • Regularly clean or replace any filters if your unit is equipped with them.
  • Inspect the system for any signs of wear or damage and address any issues promptly.

Conclusion

Installing a tankless water heater can provide many benefits, including energy efficiency and unlimited hot water. However, it requires careful attention to detail during the installation process. By avoiding these common mistakes---such as improper sizing, inadequate venting, and poor placement---you can ensure that your system operates safely and efficiently. If you are unsure about any part of the installation process, it's always a good idea to consult a professional plumber or electrician to ensure the job is done right.