How Does Hard Water Impact a Tankless Water Heater?


Tankless water heaters are popular among homeowners seeking energy-efficient and space-saving solutions for their hot water needs. These systems are known for their on-demand hot water production, which can be highly efficient when functioning correctly. 

However, hard water is a common issue in many regions and can have a detrimental impact on the performance and longevity of tankless water heaters

In this guide, we’ll delve into the effects of hard water on tankless water heaters, including how these systems work and the various methods for treating hard water in this context. Plus, we will discuss where to find the best HVAC services for dealing with hard water in Tennessee.

Read on to discover how hard water impacts your tankless water heater!

What is Hard Water?

Hard water is a common water quality issue that arises due to the presence of high levels of dissolved minerals, primarily calcium and magnesium. These minerals enter the water as it percolates through rocks and soil, and their concentration increases as the water travels through aquifers and underground sources.

When this mineral-laden water is heated or left to stand, the minerals tend to precipitate and form limescale deposits, which can accumulate in pipes, appliances, and plumbing fixtures.

According to the U.S. Geological Survey, water can fall into four main categories:

  • Soft: 0 to 60 milligrams per liter (mg/L) as calcium carbonate
  • Moderately hard: 61 to 120 mg/L as calcium carbonate
  • Hard: 121 to 180 mg/L as calcium carbonate
  • Very hard: More than 180 mg/L as calcium carbonate

Although hard water is not considered a health hazard, it can be harmful to your plumbing and appliances. Additionally, hard water can sometimes irritate your hair and skin, causing them to dry out over time. 

As such, seeking professional guidance for dealing with your hard water problem is vital. 

How Does a Tankless Water Heater Work?

Before exploring the effects of hard water on tankless water heaters, it is essential to understand how these systems function. 

Unlike traditional tank-based water heaters that store and continuously heat a large volume of water, tankless water heaters heat water as needed, providing hot water on demand. 

Here’s a simplified overview of how a tankless water heater works:

  • Cold Water Inlet: When you open a hot water tap or use an appliance that requires hot water, cold water enters the tankless water heater unit.
  • Heat Exchanger: Inside the tankless water heater, there’s a heat exchanger. This is where the heat source, typically a gas burner or an electric element, rapidly heats the cold water as it flows through the heat exchanger.
  • Hot Water Outlet: The now-hot water is delivered to your faucet or appliance almost instantly.
  • No Standby Heat Loss: Unlike traditional water heaters, tankless units have no storage tank. This eliminates standby heat loss, which can be a significant source of energy inefficiency.

Tankless water heaters offer several key benefits that make them a popular choice among homeowners. These benefits include: 

  • Energy Efficiency: Since they only heat water when needed, tankless water heaters are highly efficient and can lead to energy savings on your utility bills.
  • Continuous Hot Water: Tankless systems provide a continuous supply of hot water, as long as they are appropriately sized for your needs.
  • Space-Saving Design: Their compact size and wall-mountable installation make them an excellent choice for homes with limited space.
  • Longevity: Tankless water heaters typically have a longer lifespan compared to traditional tank water heaters, often exceeding 20 years.
  • Reduced Risk of Water Damage: The absence of a storage tank reduces the risk of leaks and water damage.

Hard Water Effects on a Tankless Water Heater

Hard water can significantly impact the performance and longevity of tankless water heaters due to its mineral content. The primary effects of hard water on these systems are as follows:

  • Limescale Buildup: As hard water is heated within the tankless water heater, calcium and magnesium ions in the water precipitate and form limescale deposits. These deposits can accumulate on the heat exchanger, reducing its efficiency and the unit’s overall performance.
  • Reduced Efficiency: The limescale buildup acts as an insulating layer on the heat exchanger, making it less effective at transferring heat to the water. This leads to increased energy consumption and potentially longer wait times for hot water.
  • Shortened Lifespan: Prolonged exposure to hard water can lead to more significant limescale buildup and corrosion within the tankless water heater, ultimately reducing its lifespan. In turn, you may face additional expenses for water heater repairs or replacements. 
  • Clogging and Reduced Flow: Limescale deposits can accumulate in the plumbing and components of the tankless unit, potentially leading to clogs and a decrease in water flow rate. This can disrupt your home by disturbing the functionality of your plumbing system. 
  • Maintenance Costs: Hard water-related issues can increase maintenance and repair costs to keep the tankless water heater functioning properly. When calculating maintenance costs, you must also consider the labor costs associated with HVAC services and solutions. 

Hard Water Treatment for a Tankless Water Heater

To mitigate the negative impact of hard water on your tankless water heater, various treatment options are available. Implementing one or a combination of these methods can help extend the life of your tankless system and maintain its efficiency.

Let’s take a look at the main types of hard water treatments to know about: 

  • Whole House Water Softener: Installing a whole-house water softener is one of the most effective solutions to combat hard water issues throughout your home. Water softeners use ion-exchange technology to replace calcium and magnesium ions with sodium ions, effectively softening the water. Softened water reduces limescale buildup in the tankless water heater and protects other appliances within the home. 
  • Point-of-Use Water Filter: In situations where installing a whole-house water softener is not feasible or necessary, a point-of-use water filter can be an effective solution. These filters are installed directly at the point where water is used, such as under the kitchen sink or near the tankless water heater. They are designed to remove minerals and other contaminants that can cause limescale buildup.
  • Flow Tech: Flow Tech is a water treatment technology designed to prevent limescale buildup in tankless water heaters and other appliances. It utilizes a physical water treatment system that alters the behavior of minerals in the water, preventing them from adhering to surfaces and forming deposits. Flow Tech is a maintenance-free option that can be installed at the water main or at specific appliance points.
  • High-Pressure Tankless Water Heater: Opting for a tankless water heater with high pressure or high flow technology can help reduce the effects of hard water. These units are engineered to handle harder water conditions more effectively, reducing limescale buildup and maintaining performance.
  • Tankless Water Heater Cleaning: Regular maintenance and cleaning of your tankless water heater can help remove existing limescale deposits and prevent further buildup. Cleaning procedures typically involve flushing the unit with a descaling solution to break down and remove limescale. This type of cleaning procedure often requires assistance from a professional HVAC team to ensure the quality of your water and appliances. 
  • Tankless Water Heater Maintenance: Scheduled maintenance by a professional technician can ensure that your tankless water heater is operating at peak efficiency. This includes inspecting for signs of limescale, cleaning the unit, and promptly addressing any issues. Finding a reliable HVAC provider in your area that offers specialized tankless water heater services is key. 
  • Descale Tankless Water Heater: Descaling is the process of removing limescale deposits from the tankless water heater’s heat exchanger and other components. Descaling should be performed as part of regular HVAC maintenance and typically involves the use of a descaling solution that helps with flushing out the deposits.

Ultimately, dealing with a hard water problem swiftly is essential for ensuring the longevity of your tankless water heater. Working with a professional HVAC provider is the key to ensuring your water heater is well-maintained and protected from the adverse effects of hard water. 

Hard Water In My Area: Tennessee

In the table provided below, we outline the hard water levels in various areas of Tennessee. Knowing the extent of hard water in your area is essential as it empowers you to make informed decisions about the impact on your pipes, appliances, and plumbing systems. Being aware of the hardness level enables you to implement precautionary measures effectively, ensuring the longevity and efficiency of your household essentials.

Final Thoughts: The Best Hard Water Services in Tennessee 

Hard water is a common water quality issue that can harm the performance and longevity of tankless water heaters. The accumulation of limescale deposits within the unit can reduce efficiency, increase energy consumption, and potentially shorten the system’s lifespan. 

Choosing the most suitable treatment method for your water heater is vital to mitigate these effects.  

Implementing one or a combination of the above-discussed solutions will help ensure that your tankless water heater continues to provide efficient, on-demand hot water for years to come.

If you live in Tennessee and are searching for a reliable HVAC provider to help resolve your hard water problems, Rapid Response Heating and Cooling is here to help. 

Rapid Response Heating and Cooling is Tennessee’s #1 choice for heating and air conditioning solutions, servicing the communities of Brentwood, Franklin, Spring Hill, Columbia, Thompson’s Station, Fairview, Nashville, Antioch, and Portland. Rapid Response’s HVAC services include:

  • Heating
  • Air Conditioning 
  • Heat Pumps
  • Water Heaters
  • Air Quality

As a fully licensed and insured HVAC provider, Rapid Response Heating and Cooling provides the top-notch professional service you need to rid your home of its hard water woes.Get in touch with Rapid Response Heating and Cooling today to request a quote.

Looking for an HVAc Professional in Brentwood, TN?

We are the right choice for all your HVAC needs! Here at Rapid Response, we understand that no two customers are the same and that is why our team of trained professionals will go above and beyond to meet the customized cooling needs of every customer. By choosing us you will receive fair rates, quality work and outstanding service.