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5 Common Mistakes To Avoid When Installing A Tankless Water Heater

Installing a tankless water heater can be a game-changer for your home’s energy efficiency and convenience, but it’s crucial to avoid common mistakes that can lead to poor performance or even safety hazards. Here’s a comprehensive guide to the five most common mistakes to avoid when installing a tankless water heater, ensuring a smooth and successful installation. Along the way, we’ll delve into detailed explanations, practical tips, and the importance of each aspect, creating an extensive guide to help you make the most informed decisions.

1. Incorrect Sizing

Understanding The Importance Of Proper Sizing

One of the most critical mistakes when installing a tankless water heater is choosing the wrong size. A unit that is too small won’t be able to meet your household’s hot water demands, while an oversized unit can lead to wasted energy and unnecessary expenses.

Calculating Your Hot Water Needs

To choose the right size, you need to determine your household’s peak hot water demand, measured in gallons per minute (GPM). Consider all the fixtures and appliances that might be used simultaneously. Here’s a rough guide:

  • Shower: 2-3 GPM
  • Dishwasher: 1-2 GPM
  • Washing Machine: 1.5-2 GPM
  • Kitchen Faucet: 1-2 GPM

Example Calculation

If your household might run a shower (3 GPM), a washing machine (2 GPM), and a kitchen faucet (1.5 GPM) at the same time, you would need a tankless water heater with a capacity of at least 6.5 GPM.

Consequences Of Incorrect Sizing

Choosing an incorrectly sized unit can lead to insufficient hot water during peak usage times or excessive energy consumption, impacting both comfort and utility bills. Therefore, accurate calculation and appropriate sizing are paramount.

2. Improper Venting

The Role Of Venting In Tankless Water Heaters

Proper venting is crucial for gas-powered tankless water heaters to prevent the buildup of harmful gases like carbon monoxide. Incorrect venting can lead to dangerous situations, including gas leaks or backdrafting.

Types Of Venting

  • Direct Venting: Uses two pipes—one for bringing in fresh air from outside and the other for expelling exhaust gases. This method is safer and more efficient.
  • Power Venting: Uses a single pipe to expel exhaust gases, with air drawn from inside the house. Requires a powered vent fan.

Installation Tips

  • Use Proper Materials: Only use venting materials recommended by the manufacturer, such as stainless steel or PVC, depending on the model.
  • Correct Sizing: Ensure the vent pipes have the correct diameter and length as specified in the installation manual.
  • Safe Routing: Route vent pipes to avoid any dips or bends that could trap exhaust gases.

Consequences Of Improper Venting

Improper venting can result in incomplete combustion, leading to the buildup of dangerous gases inside your home. This not only affects the efficiency of the unit but also poses serious health risks.

3. Ignoring Electrical Requirements

Importance Of Meeting Electrical Specifications

Electric tankless water heaters have specific electrical requirements that must be met to ensure safe and efficient operation. Ignoring these requirements can lead to electrical issues or even fire hazards.

Key Electrical Considerations

  • Amperage: Ensure your home’s electrical system can handle the amperage required by the unit. Electric tankless water heaters often require 120-200 amps.
  • Voltage: Most units require a dedicated 240-volt circuit.
  • Wiring: Use the correct gauge wiring as specified by the manufacturer to handle the electrical load.

Upgrading Your Electrical System

In some cases, you may need to upgrade your electrical panel to accommodate the tankless water heater. This can be an additional expense but is necessary for safe operation.

Consequences Of Ignoring Electrical Requirements

Failing to meet the electrical requirements can result in frequent tripping of breakers, inadequate heating performance, or even electrical fires. Always consult with a licensed electrician to ensure proper installation.

4. Poor Location Choice

Selecting The Optimal Location

The location of your tankless water heater affects its efficiency, accessibility for maintenance, and overall performance. A poorly chosen location can lead to higher energy consumption and reduced lifespan of the unit.

Factors To Consider

  • Proximity To Water Sources: Install the unit close to the primary points of use (e.g., bathrooms, kitchen) to minimize the delay in hot water delivery and reduce water wastage.
  • Access For Maintenance: Ensure there is sufficient space around the unit for easy access during maintenance or repairs.
  • Environmental Conditions: Avoid installing the unit in areas prone to extreme temperatures, moisture, or dust, as these can affect the unit’s performance and longevity.

Installation Tips

  • Indoor VS. Outdoor Units: Choose the appropriate model based on where you plan to install it. Outdoor units are built to withstand weather conditions but need protection from freezing.
  • Mounting: Ensure the unit is securely mounted on a wall that can support its weight and provide proper clearance as specified by the manufacturer.

Consequences Of Poor Location Choice

A poorly chosen location can lead to inefficient operation, increased wear and tear, and difficulty in accessing the unit for necessary maintenance, ultimately reducing its lifespan and effectiveness.

5. Neglecting Regular Maintenance

Importance Of Maintenance

Regular maintenance is crucial to ensure the efficient and long-lasting operation of your tankless water heater. Neglecting maintenance can lead to decreased performance, higher energy bills, and potential damage to the unit.

Key Maintenance Tasks

  • Descaling: Hard water can cause mineral buildup inside the heat exchanger, reducing efficiency. Descale the unit regularly, especially in areas with hard water.
  • Cleaning The Inlet Filter: The inlet filter should be cleaned periodically to prevent debris from clogging the unit.
  • Inspecting The Venting System: Ensure the venting system is clear of obstructions and properly sealed to prevent gas leaks.
  • Annual Professional Inspection: Have a professional inspect the unit annually to check for any potential issues and ensure everything is functioning correctly.

How To Perform Maintenance

  • Descaling: Use a descaling solution or white vinegar to flush the system, removing any mineral deposits. Follow the manufacturer’s instructions for the specific descaling process.
  • Cleaning The Inlet Filter: Turn off the water supply and remove the inlet filter. Rinse it under running water and reinstall it.
  • Inspecting The Venting System: Check for any visible signs of damage or blockage in the vent pipes and ensure all connections are secure.

Consequences Of Neglecting Maintenance

Neglecting regular maintenance can lead to reduced efficiency, higher operational costs, and potentially costly repairs or replacements. Regular maintenance ensures optimal performance and extends the lifespan of your tankless water heater.

Detailed Exploration Of Each Mistake

Mistake 1: Incorrect Sizing

Real-Life Implications

Imagine a family of four installing a tankless water heater that’s too small. They might face lukewarm showers during peak usage times, leading to frustration and the need for an additional or replacement unit. Conversely, an oversized unit can result in higher energy bills due to unnecessary heating capacity.

Advanced Sizing Considerations

  • Climate Impact: Colder climates require more heating power to achieve the same temperature rise, so consider the incoming water temperature based on your region.
  • Usage Patterns: Analyze your family’s hot water usage patterns. If multiple showers, dishwashers, and washing machines are likely to run simultaneously, opt for a higher capacity.

Mistake 2: Improper Venting

Real-Life Implications

A poorly vented gas tankless water heater can lead to dangerous carbon monoxide buildup. For instance, a family might install a unit in a confined space without adequate ventilation, resulting in health hazards and potential poisoning.

Advanced Venting Considerations

  • Vent Pipe Material: Ensure the use of corrosion-resistant materials like stainless steel, especially for condensing units that produce acidic condensate.
  • Combustion Air Supply: Ensure adequate air supply for combustion. For tight homes, consider direct vent units that draw air from the outside.

Mistake 3: Ignoring Electrical Requirements

Real-Life Implications

Installing an electric tankless water heater without upgrading the electrical panel can lead to frequent breaker trips, especially if other high-demand appliances are in use. This can cause inconvenience and potential damage to the electrical system.

Advanced Electrical Considerations

  • Load Calculation: Conduct a detailed load calculation to determine if your existing electrical panel can support the new load. Consider other high-power appliances in the calculation.
  • Circuit Breaker Compatibility: Ensure the circuit breaker is compatible with the tankless unit’s requirements and is appropriately rated for safety.

Mistake 4: Poor Location Choice

Real-Life Implications

A tankless water heater installed in a damp basement might suffer from corrosion and reduced lifespan. Similarly, a unit installed far from the primary points of use might result in a delay in hot water delivery, wasting water and energy.

Advanced Location Considerations

  • Temperature Fluctuations: Avoid installing in areas with significant temperature fluctuations, as extreme cold can cause freezing and damage to the unit.
  • Noise Concerns: Some units can be noisy during operation. Consider installing them in a location where noise won’t be a disturbance.

Mistake 5: Neglecting Regular Maintenance

Real-Life Implications

A tankless water heater in a hard water area without regular descaling can suffer from mineral buildup, reducing efficiency and increasing energy consumption. Over time, this can lead to costly repairs or the need for replacement.

Advanced Maintenance Considerations

  • Water Quality Assessment: Regularly test water quality and consider installing a water softener if you have hard water to reduce mineral buildup.
  • Maintenance Schedule: Establish a maintenance schedule that includes regular descaling, filter cleaning, and professional inspections to ensure the unit operates efficiently.


Avoiding these common mistakes when installing a tankless water heater can ensure a successful and efficient upgrade to your home’s hot water system. Proper sizing, correct venting, meeting electrical requirements, choosing the optimal location, and regular maintenance are all critical factors that contribute to the longevity and performance of your tankless water heater.

By understanding and addressing these potential pitfalls, you can enjoy the numerous benefits of a tankless water heater, including energy efficiency, space-saving, and endless hot water supply. Always consult with professionals for installation and maintenance to ensure safety and optimal performance.

If you have any further questions or need personalized advice, feel free to reach out. We’re here to help you make the best choice for your home’s hot water needs.

Experience Excellence In Tankless Water Heaters With Garcia Plumbing And Home Restoration!

We understand the importance of having a reliable and efficient water heating system in your home. Our dedicated team of licensed experts leads the way in providing exceptional tankless water heater solutions that ensure both energy efficiency and consistent performance.

Beyond just water heater installations and repairs, Garcia Plumbing and Home Restoration offers comprehensive home maintenance solutions. Our reputation in Contra Costa County is built on unwavering quality, unmatched expertise, and the trust of numerous satisfied clients. Don’t compromise when it comes to your home’s comfort and energy efficiency. Contact us today for outstanding tankless water heater services and embrace a worry-free plumbing future!

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