Best Tankless Water Heaters for Hard Water: Reviews & Buying Guide

Lime Scaling can be a serious issue especially if it accumulates in the pipes for a long time without any maintenance or monitoring. Thus, impacting the overall performance of tankless water heaters, especially when used with hard water. However, manufacturers have come up with specialized tankless water heaters that are designed specifically to solve the issues associated with heating hard water.

These products are integrated with scale detection abilities that enable them to monitor the accumulation of dissolved salts in the pipes and other significant components of the heater. Furthermore, they also notify the user in case of potential accumulation and allow you to take necessary precautions in this regard. However, not everyone is aware of the exceptional benefits these models have to offer, and therefore, we present a detailed review on the best tankless water heater for hard water along with a buying guide to help you enjoy a hassle-free hot water shower.

Best Tankless Water Heater for Hard Water – Top 4 Pick Reviews

1. Stiebel Eltron Tankless Water Heater

Stiebel Eltron Tempra 24 Plus Tankless Water Heater

Stiebel Eltron Tankless Water Heater is a perfect example of a lightweight and easy-to-install electric tankless water heater available for regular use. Despite its compact size and negligible requirements, it is capable of offering a consistent hot water supply throughout your house without any interruption or performance issues. The heater operates at the flow rate of 3.64 gallons per minute and, therefore, is extremely time-efficient in nature.

You can achieve an endless supply of hot water without consuming additional time. Another highlighting and worthy attribute of this product is the inclusion of the advanced flow control that monitors the amount of incoming water and decreases the risk of hot water shortage in case of high demand. This improves the overall performance and the output of the system and adds five stars to its abilities.

In addition to this, we also found the heater suitable for outdoor as well as indoor use because of its low ventilation requirements and stylish design, which can further enhance the beauty of your apartment. Moreover, the model does not produce loud noise while working and is characterized by an extremely silent operation. This enables you to install it anywhere you like with little concern regarding adjustment or disturbance.

Finally, it does not require continuous maintenance or repeated descaling because of its high quality and durable construction, which protects it from damage due to multiple factors. The most common among which include the scaling of the pipes because of salt accumulation, thus, making it an ideal option for hard water use.

  • Automatic temperature regulation
  • Copper heating modules
  • Remarkable digital display
  • Expensive

Stiebel Eltron Tankless Water Heater is considered the best tankless water heater for hard water. Its user-friendly design and trouble-free operation enable you to operate it conveniently. Thus, coupled with the inclusion of the digital temperature display and electronic switch to operate the heater further improves the performance and is the reason for its immense popularity among users.


2. Rheem RTEX-24 Electric Tankless Water Heater

Rheem Electric Tankless Water Heater

Rheem RTEX-24 Electric Tankless Water Heater is yet another outstanding option included in this article on the best tankless water heater for well water. The product comes with an on/off dial control that allows you to adjust the temperature according to the need and availability of hot water. Along with this, a digital temperature display is also present, which displays the temperature of the water and notifies you that the temperature needs to be regulated.

This allows you to respond in time, thus, improving the overall performance and the net output generated by the heater. Similarly, the power input is also adjustable in nature and can be automatically adjusted by the system thanks to the inclusion of the self-modulating technology. Self-modulation regulates the amount of power consumed by the system and hence, contributes to the energy-efficiency in the long term.

Another benefit offered by the low power consumption is the decreased electric bill which prevents your budget from straining at the end of the month. Apart from these features, we also appreciate the large water flow rate, which ensures the provision of endless hot water in three different bathrooms at a time.

The flow rate is 5.9 GPM which is associated with a consistent hot water supply throughout the day and relieves you from the worries of running out of water while taking a shower or performing other house chores. Last but not least, the heater can be installed at the point of use due to its small size and offers on-demand hot water. Thus, it not only conserves energy for future use but also reduces the consumption of water.

  • Consistent hot water
  • High durability
  • Easy to install
  • Not for commercial use

Rheem RTEX-24 Electric Tankless Water Heater is manufactured using durable substances that are not prone to damage due to salt accumulation and changing weather conditions. Furthermore, it does not need continuous descaling instead, you only need to descale it once or twice a year. So, we highly suggest using it with hard water to fulfill your basic requirements without any performance inefficiency or maintenance concerns.


3. Rinnai V75iP Propane Tankless Water Heater for Well Water

Rinnai Tankless Water Heater

Rinnai V75iP Propane Tankless Water Heater is a compact and stylish heating unit that features a large water flow rate and is perfect for accommodating the growing hot water demand for both residential and commercial purposes. The durable piping and outer body of the product make it an ideal option for outdoor locations, and therefore, you can easily install it at any suitable outdoor location without any major durability issues.

Moreover, the outdoors also offers a perfect platform for air circulation and contributes to remarkable ventilation. Thus, preventing the system from overheating even after continuous use for long hours. In addition to this, it offers on-demand hot water and, therefore, is characterized by energy efficiency and limited water use.

This means that the system will only heat the water whenever it is required and will not use excessive power or propane for heating the water. Hence, cutting down on your monthly electricity and gas expenditure. Similarly, the large water flow rate of 7.5 gallons per minute ensures an uninterrupted supply of hot water and ensures that you do not run out of hot water during daily tasks.

However, besides all this, we were highly impressed by the enhanced scale detection abilities of the heater, which can immediately detect the accumulation of the salts in the pipes and notify you within time. Thus, protecting you against unwanted damage and regular descaling of the unit. This attribute increases the suitability of this propane heater for hard water and makes it the best tankless water heater for hard water available on the market these days.

  • Effortless installation
  • Space-saving design
  • Remarkable scale detection
  • Issues with the venting pipe

Rinnai V75iP Propane Tankless Water Heater is relatively easier to install and does not require an expert technician for this purpose. Therefore, you do not need to spend additional money for this purpose. Additionally, its high durability is attributed to the superior design, which prevents it from breaking or scratching due to multiple factors. Thus, making it our utmost choice for regular use, especially for residential applications.


4. EcoSmart ECO 11 Electric Tankless Water Heater for Hard Water

EcoSmart Eco 11 Tankless Water Heater

EcoSmart ECO 11 Electric Tankless Water Heater is an environmentally friendly option that is characterized by high durability, lightweight, and compact design, which allows you to install it anywhere in both indoor and outdoor locations. Furthermore, it does not require any venting and, therefore, can be stored in a confined area without worrying about overheating or other related performance issues.

The installation is also relatively easy, and you do not need any external guidance or help for this purpose. Along with this, it can be installed at the point of use because of its small size and contributes to remarkable energy efficiency. This is because of its minimum power consumption and heating requirements which saves you additional electricity costs. It also heats water on demand and saves water for future use.

We have found it to be 99% thermal efficiency as compared to the other options included in the list. Besides these attributes, we also admire the automatic temperature adjustment that regulates the flow of hot water throughout the day and reduces the water shortage to a great extent. We highly recommend using it for small-scale residential applications that do not require large flow rates for hot water.

It offers a flow rate of around 3 gallons per minute and can easily accommodate your basic needs. Finally, it is not prone to damage due to the accumulation of salts inside the pipes and notifies you of excessive accumulation so that required precautionary measures can be taken in this regard. Therefore, it is our ultimate recommendation if you are searching for the best tankless water heater for hard water.

  • Energy-saving design
  • Self-modulation abilities
  • User-friendly controls
  • Warranty issues

EcoSmart ECO 11 Electric Tankless Water Heater is integrated with self-modulation technology that monitors and regulates the power and energy consumption of the product, thus, enabling you to save some money on your electricity bills. Furthermore, its high durability and sustainable design allow you to use it both indoors and outdoors without any performance issues or maintenance requirements.


Factors to Consider While Purchasing the Best Tankless Water Heater for Hard Water

Hard water contains various salts and ions that can damage the pipes and other significant components of tankless water heaters, and therefore, you should carefully monitor and access the features of these products before investing in them for long-term benefits. We have compiled a list of various factors that can be taken into account while purchasing tankless water heaters and have discussed them in detail for your reference.

Scale Detection

Scale detection abilities of the heater are highly important, especially if you are planning to use it for heating hard water. Hard water contains salts and ions of various chemical compounds that can damage the pipes and other crucial components of these products. Thus, leading to performance issues as well as high maintenance costs.

The scale detection enables you to monitor the accumulation of salts in these areas and notifies you immediately. Thus, protecting the unit against serious damage and contributing to reduced maintenance costs in the long term. So, it is important to invest in the options that display outstanding scale detection abilities and do not require regular maintenance. However, keep in mind that despite the scale detection, you must descale the heater once every year to extend its average life and protect it against deterioration.

Energy Efficiency

It refers to the ability of the heater to consume energy required for regular functioning. Some heaters might not be energy efficient in nature and might consume additional input gas and power in order to function properly. Avoid using such products as they will not only consume high power but will also lead to increased electricity bills. Hence, leads to financial issues.

Instead, you should choose models that are integrated with self-modulation technology and can automatically regulate energy consumption and power usage depending upon the requirement. This will not only conserve energy for future use but will also cut down on your monthly bill. Apart from this, to save energy, you can also purchase heaters that heat up water on demand and can be installed at the point of use for negligible heating requirements and best results throughout the day.

Gas or Electricity Powered System

Another factor that can significantly impact your decision to purchase a particular product is the power generation mechanism. You should carefully decide whether you want to invest in a gas-powered or an electricity-powered tankless water heater. Gas-powered products feature a large flow rate and require negligible time for heating water, and are more suited to commercial applications. However, they are not environmentally friendly and are available at relatively high prices.

In contrast, the electric water heaters take time to heat up water and have a relatively slower water flow rate. So, they can be used for small-scale residential applications. They are also budget-friendly and are available at a relatively low price across the market. Moreover, these units are energy-efficient in nature and do not consume a lot of power to heat up the water, and are generally characterized by low electricity bills.

But, they can not be used for large-scale commercial applications. No matter whichever product you decide to buy at the end of the day, remember to check its installation mechanism. Never invest in products that are difficult to install and require technicians for this purpose as it can further incur additional costs on the heater and will lead to over-straining of your monthly budget.

Frequently Asked Questions

Do I really need a special water system for hard water?

Well, it is highly dependent on the hardness of the water. If your water contains a smaller amount of dissolved salts and ions, you can go with the regular heating systems with timely descaling. However, if the amount of dissolved salts in the hard water is higher than expected, then it is advised to go with options that possess exceptional scale detection abilities to protect the pipes and other components from getting damaged, mainly due to the accumulation of calcium salts.

Does hard water affect tankless water heaters?

Yes, hard water can significantly affect the overall performance and average life of tankless water heaters. Hard water contains high amounts of dissolved salts, mainly calcium carbonate, that can accumulate in the pipes of the heater and can cause irreversible damage in severe cases. Furthermore, the accumulated salt can only be removed after descaling which is highly expensive and can lead to financial constraints for some users.

Is a water softener required for a tankless water heater?

Generally, water softeners are not used with tankless water heaters. However, using one can be highly beneficial as it can reduce the accumulation of salts in the pipes. Thus, leading to lower maintenance and descaling requirements. Furthermore, it also reduces the overall operational expenses of the heater and increases its suitability for users with diverse financial backgrounds.

Wrapping Up

Tankless water heaters are highly prone to the accumulation of dissolved salts and lime scaling, mainly due to the presence of hard water. This can significantly impact their overall performance. Thus, we have developed a detailed review of the best tankless water heater for hard water, along with various factors that can be taken into account during the selection process.

The analysis of the above-mentioned options suggests that Stiebel Eltron Tankless Water Heater is the best among its counterparts in terms of temperature regulation, user-friendliness, ventilation, durability, energy efficiency, and installation requirements. Thus, it is perfect for those searching for a durable yet lightweight tankless water heater for regular use.


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With years of experience under his belt, Adam decided to put his water heater knowledge to work. By providing high-quality content and expert guides, Adam hopes to help anyone looking for expert water heater advice.