Best Tankless Water Heater For Hard Water? (2021 Review)

Last Updated On October 19, 2021
tankless water heater hard water (1)

Have you noticed a strange film on your hands after washing them, spots on glasses fresh out of the dishwasher, or soap scum on the tub? This is likely due to hard water. 

Hard water, water with heavy concentrations of minerals in it, is not just an annoyance – it can also slowly deteriorate the plumbing and appliances in your house, including your tankless water heater!

To avoid the costs of repairs and early water heater replacement, you need to buy the best tankless water heater for hard water conditions. 

In this PlumbingNav guide, we will cover: 

  • Different types of tankless water heaters for hard water
  • How does a tankless water heater work? 
  • What should I look for when looking for a tankless water heater for hard water?
  • Review of 5 Best Tankless Water Heaters for Hard Water

ImageProduct
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Ecosmart ECO 36 Electric Water Heater
  • Lifetime warranty
  • 99.8% efficiency
  • 8.7 GPM
  • Lifetime warranty
  • 99.8% efficiency
  • 8.7 GPM
View on Amazon
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Rinnai RL+ Non-Condensing Tankless Gas Water Heater
  • 9.8 GPM
  • Trusted Rinnai brand name
  • Circulation technology
  • 9.8 GPM
  • Trusted Rinnai brand name
  • Circulation technology
View on Amazon
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Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater
  • Low weight
  • 99% efficiency
  • No T&P valve required
  • Low weight
  • 99% efficiency
  • No T&P valve required
View on Amazon
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Rheem RTEX-24 Electric Tankless Water Heater
  • 99.8% efficiency
  • Self-modulating technology
  • Three copper heating elements
  • 99.8% efficiency
  • Self-modulating technology
  • Three copper heating elements
View on Amazon
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Rinnai SE+ Tankless Gas Water Heater
  • 7.5 GPM
  • WiFi compatible
  • .93 Efficiency
  • 7.5 GPM
  • WiFi compatible
  • .93 Efficiency
View on Amazon

Our Overall #1 Rated Pick

Updated On May 21, 2021

Ecosmart ECO 36 Electric Water Heater

This compact electric tankless water heater produces up to 8.7 GPM of hot water in both indoor and outdoor settings at 99.8% efficiency. You can see the temperature on the digital display and change the temperature with the knob on the unit. It has a copper heat exchanger that can be easily replaced if necessary, and it comes with a limited lifetime warranty. 

Our Top Tankless Water Heaters for Hard Water

Quickly uncover our picks for the top 5 tankless water heaters for hard water before we go over the topic in more detail. 

  1. Ecosmart ECO 36 Electric Water Heater (Best Overall)
  2. Rinnai RL+ Non-Condensing Tankless Gas Water Heater  (Best High End)
  3. Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater (Best Value)
  4. Rheem RTEX-24 Electric Tankless Water Heater (Best Efficiency)
  5. Rinnai SE+ Tankless Gas Water Heaters (Most User-Friendly)

What's In This Guide?

      What Are The Best Tankless Water Heaters For Hard Water

      The best tankless water heaters for hard water contain heavy-duty heating elements that can withstand the sediment buildup that develops inside of the unit as a result of the high mineral content in the hard water. 

      Sediment buildup on the heating element can hinder its ability to communicate with the thermostat, causing the device to produce water at scalding temperatures. To prevent this from happening, you can buy a tankless water heater that includes heating elements made out of durable material. 

      Types of Heating Elements 

      The main difference between the types of heating elements comes down to the material used to create them. 

      A mixture of stainless steel and nickel creates high-end heating elements known as ultra low watt-density elements. These heating elements have a larger surface area, giving them the ability to spread out the heat, lowering the temperatures it faces and reducing damage. 

      The materials increase the component’s ability to thwart off calcium deposits and corrosion, allowing it to last longer under hard water conditions

      High watt-density heating elements, on the other hand, contain copper and zinc. These elements generate a large amount of heat, making them more vulnerable to damage. The copper doesn’t protect against the sediments buildup as well, either. 

      For the best tankless water heater for hard water, pick a device with ultra-low density stainless steel heating elements. 

      What Are The Different Types Of Tankless Water Heaters For Hard Water?

      The two types of tankless water heaters for hard water are gas tankless water heaters and electric tankless water heaters. Both options can withstand hard water if you get the right hot water heater, but they have other distinctive features that make each one better in certain situations. 

      Gas Tankless Water Heater

      Gas water heaters heat the water using a gas burner with a direct flame to ignite the heat exchanger, which heats the water. 

      Gas doesn’t cost as much as electricity, and gas water heaters tend to heat water more quickly. 

      Also, many high-efficiency condensing gas water heaters provide efficiency ratings that match the efficiency levels of electric water heaters. 

      However, gas tankless water heaters cost more both for the unit itself as well as the more complicated installation. The direct heat can also increase the likelihood of sediment buildup, requiring more frequent maintenance. 

      Electric Tankless Water Heaters 

      Electric tankless water heaters use indirect heat to spark the heat exchanger. Since the process generates less heat, it takes slightly longer to heat the water. However, this also leads to high energy efficiency levels, and more protection from sediment build up than gas water heaters, which is exactly what you need when you have hard water. 
      However, electric water heaters don’t produce the same power as gas water heaters, and electricity costs more than gas.

      did you know best tankless units for hard water (1)

      How Does A Tankless Water Heater For Hard Water Work?

      Tankless water heaters produce hot water on demand as opposed to tank-style units that constantly run to keep the water in the tank warm, making tankless water heaters much more efficient than traditional tank-style water heaters. 

      When you turn on the hot water faucet, water comes into the unit at the cold water supply line. When this happens, it activates the heating element, which heats the water. The hot water then travels to the open faucet. 

      The hot water flows continuously until you close the faucet or additional faucets demand a higher water flow rate than the unit can provide. 

      What Do You Look For In The Best Tankless Water Heater For Hard Water?

      When looking for the best tankless water heater for hard water, you need a tankless water heater that can accommodate your home’s needs and the initial expense compared to the monthly savings. 

      Water Flow 

      Unlike tank-type water heaters that use a tank, tankless water heaters measure the size of the unit based on water flow in gallons per minute (GPM). 

      To ensure you get the correct size water heater, first determine how much water your family uses at peak hours. Use the following estimates to determine the proper flow rate for you:

      • 2 bedroom/1 bathroom – 6 GPM
      • 2 bedroom/2 bathroom – 10 GPM
      • 3 bedroom/2 bathroom – 12 GPM
      • 4 bedroom/2 bathroom – 14 GPM
      • 4 bedroom/3 bathroom – 16 GPM
      • 5 bedroom/3 bathroom – 18 GPM

      Keep in mind that tankless water heaters provide better water flow rates in warm climates compared to cold climates. Be careful to check the rating of possible units in your area.

      See the video below for help finding sizing information:

      Costs

      You need your tankless water heater to fit into your budget, so analyze the costs associated with your tankless water heater before you make a purchase. 

      Tankless water heaters tend to require a higher initial investment, but they last up to 20 years and also tend to save money in the long run. 

      Electric tankless waters won’t cost as much up front, and they have some of the highest efficiency levels. 

      If you prefer gas tankless water heaters, you can choose between non-condensing and condensing models. Condensing models cost more, but they run more efficiently. 

      Best Tankless Water Heaters For Hard Water Reviewed

      Now let’s explore our favorite units so you can decide on the perfect choice for your situation.

      Our #1 Rated Pick: Ecosmart ECO 36 Electric Water Heater

      Ecosmart ECO 36 Electric Water Heater

      Best Overall

      This compact electric tankless water heater produces up to 8.7 GPM of hot water in both indoor and outdoor settings at 99.8% efficiency. You can see the temperature on the digital display and change the temperature with the knob on the unit. It has a copper heat exchanger that can be easily replaced if necessary, and it comes with a limited lifetime warranty. 

      Pros

      • Lifetime warranty
      • 99.8% efficiency
      • 8.7 GPM

      Cons

      • No connectivity options
      • Professional installation
      • Minor repairs required

      Our #2 Rated Pick: Rinnai RL+ Non-Condensing Tankless Gas Water Heater

      Rinnai RL+ Non-Condensing Tankless Gas Water Heater

      Best High End

      The Rinnai RL+ series uses gas to generate up to 9.8 GPM of hot water, which can provide a whole home hot water system for an average two- to four-person household. It uses a non-condensing design and runs at an efficiency level of .82. 

      Rinnai offers a limited 12-year warranty on the copper heat exchange and a five-year limited warranty on all other parts and components. 

      Pros

      • 9.8 GPM
      • Trusted Rinnai brand name
      • Circulation technology

      Cons

      • .82 efficiency levels mean higher utility bills
      • Expensive
      • Indoor installation only 

      Our #3 Rated Pick: Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater

      Stiebel Eltron Tempra 29 Plus Electric Tankless Water Heater

      Best Budget

      Receive a water flow of up to 6 GPM with this electric tankless water heater. The device uses advanced self-modulating technology to learn your habits, reducing energy usage and contributing to its highly efficient operation. 

      This device comes with a protection against leaks for seven years and three-year warranty on the parts, including the copper heating elements. 

      Pros

      • Low weight
      • 99% efficiency
      • No T&P (temperature and pressure) valve required

      Cons

      • .77 GPM water flow to activate unit
      • Advanced installation
      • 6 GPM

      Our #4 Rated Pick: Rheem RTEX-24 Electric Tankless Water Heater

      Rheem RTEX-24 Electric Tankless Water Heater

      Best Efficiency

      This easy to use Rheem electric tankless water heater shows the temperature on the digital display and uses one knob to control the temperature. Self-modulating control increases the ultra-high 99.8% efficiency of the device as it produces up to 5.9 GPM.

      Pros

      • 99.8% efficiency
      • Self-modulating technology
      • Three copper heating elements

      Cons

      • 5.9 GPM
      • Complicated installation
      • May not offer whole home solution

      Our #5 Rated Pick: Rinnai SE+ Tankless Gas Water Heater

      Rinnai SE+ Tankless Gas Water Heater

      Most User-Friendly

      This Rinnai tankless gas indoor water heater operates at .93 efficiency due to its condensing technology to produce up to 9 GPM. You can read and change the temperature on the clear digital display, and you can even install an optional WiFi connectivity module. The copper heating elements come with a 10-year warranty. 

      Pros

      • 7.5 GPM
      • WiFi compatible
      • .93 Efficiency

      Cons

      • Expensive
      • Indoor installation only
      • Heavy at 62 pounds

      Final Thoughts On Tankless Water Heaters For Hard Water

      When you live in an area with hard water, the mineral deposits left behind can affect your water heater, the heating element in particular. Copper ultra-low watt heating elements provide the best protection. 

      To prevent the negative effects of sediment buildup, flush your tankless water heater regularly. 

      FAQs for Tankless Water Heaters for Hard Water

      Does hard water affect tankless water heaters?

      Yes. Hard water leads to more sediment buildup in the tankless water heater, which can damage the heating element. 

      Is a water softener required for a tankless water heater?

      While not required, your water heater (and the rest of your plumbing and appliances) will benefit from the use of a water softener if you have hard water. 

      How long do tankless water heaters last with hard water?

      Even with hard water, tankless water heaters can last up to 20 years. However, this assumes that you perform regular maintenance. 

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      I'm passionate about all things plumbing, and love sharing tips, "how-to", and reviewing the latest products to help make your project a success!

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      I'm passionate about all things plumbing, and love sharing tips, "how-to", and reviewing the latest products to help make your project a success!

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