Best Hot Water Heater For Hard Water – (Reviews & Guide 2021)

We have reviewed the best hot water heater for hard water so you can pick the right one for your needsHard water is rich in calcium, magnesium, and other minerals. The presence of these minerals in high percentages is what leads to water hardness. While hard water may not pose any threat to your health, your heater may not be so lucky.

The presence of these minerals will lead to the development of limescale in your fittings and heater. These will reduce the lifespan of your gadgets and plumbing. To ensure that hard water is not the culprit for your frequent heater changes, you need to choose a pick from our best hot water heater for hard water.

Top 7 Best Hot Water Heater For Hard Water Comparison Chart

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

We know that not having a hot water heater is a bad decision. We’re also aware that choosing the wrong heater is just as bad. Hence, after due consideration, we have put together a list of some of the best hot water heaters for hard water in the market. They are;

Best Water Heater for Hard Water Review (Updated List)

1. BOSCH TRONIC  3000 T Series – Best Mini-tank water heater.

Bosch Electric Mini-Tank Water Heater Tronic 3000...
  • CONVENIENT HOT WATER HEATER: 7 gallon point-of-use mini-tank fits under your sink to provide hot water right where you need it. Thermal efficiency is 98%. Dimensions : 17.5 W x 17.5 H x 14.5 D Inches
  • INSTALLED VERTICALLY OR HORIZONTALLY: This larger model can be mounted vertically (5.1 gal. of water supply) or horizontally (7 gal. of water supply)- vertical orientation is installed with the cold and hot lines on top of the unit
  • RELIABLE WATER SOURCE: Easily hard-wire the 7-gallon model to provide the on-demand reliable water source your home or office needs
  • IMPORTANT INFORMATION: Heating capacity of 1440 watts and a temperature range of 65-145°F max. Operating pressure-150 psi. Water fittings-3/4 inch Male NPT. Electrical requirements (Amp 12A/Volts 120)
  • EASILY MOUNTED: Can be shelf or floor mounted. Wall mounting available in vertical orientation only (water connections on top) - bracket included. Simply tap into the cold water line and install the water heater directly at the sink to provide hot water

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

Bosch Tronic electric mini-tank water heater is available in three compact sizes. They have a sleek and attractive design that blends seamlessly to your home décor when installed in visible locations. Its compact size makes it ideal for all locations, such as kitchenette, basement, garage, patio sinks, and boat.

It is easy to install and could be mounted vertically or horizontally on the floor, wall, or shelf. To get hot water where it is needed and when it is needed, the best solution is to use the Tronic 3000 T from Bosch. It provides hot water at the point of use and comes with a temperature/pressure relief valve installed and features a simple plug-in connection.

Amazingly, it can be used for three different applications: as a sole water heating source for a single sink, as a supplement to an existing heater located far from the sink, and as a buffer installed in-line with tankless water heaters that experience intermittent cold water.  Also, it has thick foam insulation for maximum energy efficiency and glass-lined for durability.


  •       It can be mounted in various ways.
  •       It has three different applications.


  •       It supplies water only where it is fixed.



2. ECOSMART  27 Electric Tankless Water Heater – Largest Electric water heater.

EcoSmart ECO 27 Tankless Water Heater, Electric,...
  • Endless on-Demand Hot Water; Consistent hot water when you need it that never runs out; Continuously monitored water temperature and controlled flow rates ensure efficiency and consistent performance within 1 degree of selected temperature
  • Save Space; EcoSmart tankless electric water heaters are 90% smaller than traditional tank heaters; may be installed on wall or at point of use; Dimensions 17 x 17 x 3.75 inches
  • Save Energy; EcoSmart tankless electric water heaters are 99% thermal energy efficient; Only heats water when called unlike a tank heater that maintains water temperature even when not being used. Save up to 50% in water heating costs according to the Department of Energy
  • EcoSmart ECO 27 Sizing; Refer to the sizing map. Requires 3x40 AMP Double Pole Breaker, 27-kilowatt tankless electric water heater ideal for providing hot water for whole home applications; provides between 2.7 and 6.5 gallons-per-minute depending on the inlet water temperature; refer to the sizing guide to select the proper solution
  • Warranty and Certifications; Limited Lifetime Warranty on electronics, exchanger and element; UL-499 certified; ETL Listed

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

ECOSMART is the largest electric tankless where incoming water temperatures can reach as low as 37°F water heater. It saves up to 50% on water heating costs and 12 cubic feet of storage space. Hence, you have access to an endless amount of hot water at no extra cost and little space.

A significant feature is the digital temperature control that allows you to set your temperature in increments of 1 degree. You can set the temperature anywhere from 80°F – 140°F, suitable for a very cold region. Also, it is capable of heating nearly 3 gallons per minute at this low temperature and can handle up to two showers running at the same time and never run out of hot water. In warmer climates, this unit can handle four showers and one sink simultaneously.

Although you might need to ensure a few electrical requirements, it’s a little to possess to have the goody bag!


  •       It saves up to 50% of the heating cost.
  •       It heats a large amount of water per minute.
  •       Features a digital control that allows you to set your required temperature.


  •       A specific electrical requirement has to be in place for it to work.



3. Stiebel Electron Tempra Plus Tankless water heater – Compact, Sleek and Reliable

Stiebel Eltron Tankless Water Heater – Tempra 24...
  • CONTINUOUS FLOW – Advanced Flow Control patented technology invented by Stiebel Eltron, automatically maintains water temperature for constant comfort. It’ll reduce flow slightly if hot water demand exceeds capacity. Hot showers will never be interrupted again
  • SPACE & ENERGY SAVER – Its small, sleek white design saves space yet still provides endless hot water for your whole house, and no venting is required. Eco friendly unit saves energy with auto-modulation and the ability to electronically control water flow. Savings monitor even shows how much you save on energy costs
  • EASY OPERATION – Electronic switch activates the hot water heater and it’s noise free while in use. Has a digital temperature display and preset temperature and memory buttons, while the interior solid copper heating system does all the power work
  • TEMPRA 24 PLUS – This specific model is 24kW, 240V, requires a min recommended electric service of 150 A, and offers an output water temperature of 68° to 140°F. Check our guides below to compare features of our various Trend and Plus models, each available in different kW levels, Tempra Plus tankless water heaters can be set to limit the maximum hot water temperature to 109°F. This can be important in some installations to prevent the possibility of scalding.
  • WARRANTIES INCLUDED – Stiebel Eltron’s top-rated electric tankless water heaters perform with the highest standards for comfort and reliability. Our 7-Year Leakage and 3-Year Parts Warranties are included with purchase

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

Suppose you are looking for a small deluxe, yet powerful water heater. Stiebel is your assurance. It comes in a small, sleek white design that graces your home perfectly. Despite the size, it provides hot water for the whole house with no venting required.

Stiebel Electron water heater is the best definition of “Relax and be taken care of.” It automatically maintains water temperature for constant comfort and reduces the flow slightly if hot water exceeds capacity without interrupting the hot showers.

It has a digital temperature display and preset temperature memory buttons, making it very easy to operate and noise-free while in use. Also, a saving monitor which shows how much you save on energy cost.

Apart from the above, it is Eco-friendly and saves energy. However, a recommended household electric service is required. It’s worth all the comfort and reliability.


  •       It maintains water temperature for constant comfort.
  •       It features a saving monitor that shows how much you save on energy costs.
  •       It operates with zero noise.


  •       It requires a recommended household electric service.



4. Rinnai V65In-Natural Gas Tankless water heater – Best for Small and Medium Homes

Rinnai V65iN Tankless Hot Water Heater, 6.5 GPM,...
  • Endless Hot Water: Our tankless hot water heaters let you enjoy unlimited hot water flow throughout the house with a compact and durable design that fits your home and lifestyle
  • Energy and Space Efficient Tankless Gas Water Heater: This small hot water heater conserves energy, only heating when necessary; Enhanced scale detection lessens possibility of serious, long-term damage to unit
  • Optimal Water Pressure: This tankless water heater offers a high-performance hot water flow rate up to 6.5 GPM for a powerful, constant stream that serves up to 5 appliances at once
  • Professional Installation Recommended: Visit the Find a Rinnai PRO page on our website to locate a qualified technician in your area to install your tankless water heater; We do not recommend installing a water heater without a technician
  • Guaranteed to Last: 10-, 5-, and 1-year residential factory warranty for heat exchanger, labor, and parts, respectively

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

With Rinnai V65iN tankless water heater, you will never have to schedule your hot water needs again.  Rinnai circulates hot water through the pipes to provide you hot water fast,  endlessly. You can accommodate any/all family without stress.

Smart technological advancement, such as WIFI monitoring enables you to monitor the efficiency of the heater and remotely put the system on vacation mode when you go on holiday. This way, you can fix an issue and never experience a breakdown.

V65iN is the perfect combination of high efficiency, comfort, and value in a natural gas tankless water heater. Ideal for small to medium homes or remodels, compact, easy-to-install, reliable, and perfect for indoor locations. It remains at your service for as long as 20 years.


  •       It provides water endlessly.
  •       It is easy to install and durable over long periods.


  •       It uses natural gas, thus, suitable for indoor use only.



5. ECOTOUCH 55 Electric Water Heater – The point-of-use option

Tankless Water Heater 5.5kw 240V, ECOTOUCH...
  • 【INSTANT & SUFFICIENT HOT WATER】Applied with 5.5KW heating system, the electric water heater supplies instant, consistent and endless hot water of 116℉or higher temp shortly, no waiting for preheat nor terrible temp up & down, perfect companion for sinks. Time to get rid of those "lukewarm" toys.
  • 【SMART SELF ADJUSTMENT】The hot water heater adjusts power input based on flow rate and temp setting in real time. For example, less power will be applied by the system when waterflow reduced, thus you still get ideal temperature instead of scalding hot water, which means comfortable experience. Optimal energy efficiency of 98% saves considerable electric charge.
  • 【CONVENIENT USE】The tankless water heater comes with digital display & touch control panel so temp setting is easy job. Now turn on the tap and let the smart unit do the rest, you needn’t go through hard lesson about temp setting by a mixer tap without any hint. The Black model comes with Remote control, useful for installation under sink.
  • 【SAFE and DURABLE】Applied with multiple protection devices, every piece goes through strict tests to ensure 100% safe. Inner water and electricity lines are designed to run separately so as to avoid leakage or harm of scale build up. Approval by ETL and qualifies for UL, you can expect outstanding performance for years to come.
  • 【POINT of USE】The sleek tankless water heater is compact as an oatmeal box, making it possible to install anywhere close to outlet and avoid energy waste. It can be mounted horizontally, vertically, obliquely, ideal for kitchen, bar, school, hospital, community and hair salon. Please verify it is the right size for you: 5.5kW@240V; dimensions 11" x 7.5" x 2.35"; pipes fittings :1/2" NPT.

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

ECO55 is a tankless water heater that supplies water instantly, consistently, and endlessly, with optimal thermal efficiency of 98% and minimal energy cost.

The device adjusts power input based on flow rate and temperature setting in real-time, that is, small power input when water flow is reduced and vice versa. You get ideal temperature water instead of scalding hot water. Also, the inner water and electricity lines run separately to keep your water safe and avoid mineral build-up.

The sleek water heater has a mini size like an oatmeal box, thus can be installed anywhere and mounted horizontally, vertically, and obliquely in any location.

ECO55 features a digital display and touch control panel. So, the temperature setting is easy and convenient to handle irrespective of age. It is ideal for kitchen, school, office, bar, hospital, salon, and any other place.


  •       It provides hot water instantly.
  •       There is no mineral build-up or rusting.


  •       One point use; It provides hot water only where it is fixed.



6. InSinkErator HWT-00 Hot Water Tank – Perfect for your kitchen

InSinkErator HOT100 Instant Hot Water Dispenser...
  • Includes: Chrome finish instant hot water dispenser and 2/3-gallon stainless steel hot water tank
  • Delivers near-boiling water with easy-to-adjust temperature control
  • Tool-free tank connections and dry-start protection to ease installation. Hot Valve: Instant, self-closing
  • Ideal for instantly preparing hot coffee, tea, and other food, cleaning dishes, warming baby bottles, and so much more
  • Exclusive 1-Year We Come to You In-Home Full-Service Limited Warranty; That means we come to you if your water dispenser needs service within the warranty period

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

Meet your kitchen assistant, InSinkErator.                                                                                                                            

InSinkErator provides instant hot water tank anytime you need it. It complements your main kitchen faucet perfectly, dispensing filtered near-boiling water up to 60 cups per hour, exactly when you need it; for cooking, cleaning, and preparing hot beverages at home or office. You can adjust the temperature easily with the control to suit your purpose. The instant water heater saves time and energy, and it’s super easy to install.

 Designed with safety elegance and functionality in mind,  So, you can do more at a go. Make hot beverages, kick start boiling, make coffee, thaw frozen kitchen, and clean without harsh chemicals.


  •       It is easy to install.
  •       It dispenses filtered hot water up to 60 cups per hour.


  •       One point use; It provides hot water only where it is fixed.



7. RINKMO Electric Tankless Water Heater – Best, large Water Heater

Last update on 2024-05-30 / Affiliate links / Images from Amazon Product Advertising API

RINKMO Water Heater stands out on the list of best hot water heater for hard water. It could be otherwise called “The total package.” It is capable of running both shower, dishwasher, and washing machine without issue. Compared to a traditional electric heater, there is no mineral build-up and sudden temperature change while in use.

The self-modulating technology adjusts power input based on flow rate and temperature settings to enable stable water temperature. Hence it is suitable for all homes, especially those with babies.

RINKMO provides hot water endlessly, thus suitable for the whole house. You can get a steady stem of clean and fresh hot water 24/7. Commercial places are not exempted, It caters for hotels, gym centers, and restaurants, among others.

It saves cost, time, energy, and space. It comes in a small suitcase-like size and saves up to 60% of your heating cost. It is 99.8% energy efficient, and you get hot water within 3sec. No extra cost on maintenance, you do not need to replace heater coils since there is no scaling.  


  •       It provides a stable water temperature.
  •       There is no scaling or rusting; no need to clean up.
  •       It saves cost, time, energy, and space.
  •       It is capable of supplying large water endlessly.


  •       Installation requires licensed technician (plumber)



Factors To Consider When Buying Water Heaters

Before choosing the best hot water heater for hard water, you need to educate yourself about the options open to you as well as put some factors into consideration. Let’s take a look at some of the factors that should guide your choice of water heater for hard water.

1. Types of Water Heaters

Knowing the types of water heaters will help you make an informed choice of best water heater for hard water. The following are the water heater types out there in the market.

  • Traditional Storage-Tank Water Heater

The storage tank water heater is the most common type of water heater and the most widely used too. It features an insulated water tank that stores water. The water stored in the tank will be heated, and the tank insulation keeps the water warm till needed.

A storage-tank water heater usually has two valves. One is the pressure control valve that opens to reduce the pressure in the tank once it gets to 150 psi. The other is the temperature control valve that helps to moderate and reduce the temperature if it gets to 120 degrees Fahrenheit.

Although this is the most common heater type, you are limited to the supply the tank can give. If you need more, you will need to wait for the tank to heat another cycle.

Due to its nature of storing water, it is not the best type of heater for hard water. The storage will lead to limescale and mineral deposits that may reduce the lifespan of your heater, and you will need to clean it out regularly.

  • Tankless Water Heater

As the name suggests, this type of water heater does not have a tank that stores water for use. Instead, it heats water on-demand whenever it is needed.

This is great because it means you can have an unlimited supply of hot water anytime you need it. Although, you have to make sure you get the right size to meet up with your household’s supply for the heater to work effectively.

Also, tankless water heaters are the best heater type for hard water. The absence of a water tank reduces the need to store water, and this slows down the development of limescale and mineral deposits. For optimum performance, it is recommended that you clean your tankless water heater once every year.

Related articles: Best Whole House Electric Tankless Water Heater

                            : Programmable Thermostat for Hot Water Baseboard Heat

  • Heat Pump Water Heater

Hybrid water heaters make use of heat in the atmosphere and transfer it to the water. As a result, they use 60% less electricity when compared to other heaters. This heater type requires a large floor and storage space to function correctly. Some units also use thermostats such as the steam boiler thermostat. This thermostat is not only connected through Wi-Fi to your phone and your smart appliances, but you may also connect it to Alexa and your smart home system.

  • Solar Water Heater

The solar water heater draws energy from solar panels mounted on the roof. The energy drawn is moved to a closed-loop system that is then used to power and heat water stored on the tank.

It saves you money on sunny days but may become ineffective during the winter months. As a result, a backup energy source is required to keep it working during the cold months.

  • Condensing Water Heater

The condensing water heater features a water tank like the traditional storage-tank water heater, but the water is heated using a coil propped at the bottom of the tank. The coil is heated using gas fumes, which in turn heats the water.

Here’s video to help you recap the types of water heaters.

2.    Design

There are numerous hot water heaters for hard water out there in various styles and designs. It is essential to opt for models that would complement your home and not look odd in your home’s set up.

3.    Price

While putting other factors into consideration, your budget will largely determine your choice of best water heater for hard water. You must opt for a unit that has the size and capacity to meet your household’s needs.

It is better to spend on the heater that will provide your home with the needed hot water supply than constrain your choice based on budget.

Frequently Asked Questions

  • Which water heater is best for hard water?

A water treatment system can be incorporated in the traditional storage tank heater and other types of heaters, which makes them great for hard water as well. However, if you want a water heater that saves you from the hassles of hard water, then tankless water heaters are your best bet.

  • How long do hot water heaters last with hard water?

The standard lifespan of a water heater is between eight to twelve years. Although not typical, some homeowners get fifteen years span from their heater. If your water heater is continually exposed to hard water without treatment, expect the lifespan of your heater to be considerably lesser than the standard.

  • Is hard water bad for the water heater?

Yes. Hard water is bad for gadgets and electronic appliances. It reduces the efficiency and lifespan of your water heater. The minerals in hard water will lead to the development of mineral deposits and limescale in your water heater.

  • How do you clean hard water from a hot water heater?

Hard water can be cleaned from your water heater by flushing your water heater. You can also add vinegar into the water in the water heater and heat it to help clean it of hard water.

  • How can I test the hardness of water?

You can test your water for hardness by washing your hands. If you have the feeling that your hand is not completely clean, that is soap scum caused by a reaction between the calcium in the water and the soap used.


Hard water, when left unchecked, can damage your water heater, make it inefficient and reduce the lifespan. To prevent all these, we have taken our time to research and come up with top picks of the best water heater for hard water.

The water heaters reviewed were chosen based on how effective they are with hard water, amongst other considerations. Choosing from the list means you have to worry less about hard water causing damage to your water heater.

You can choose from the products we have reviewed extensively above, or you can use our buyer’s guide section to guide your choice of the best water heater for hard water.



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Ronald Watford, the owner of Quality Home Air Care, is a qualified HVACR technician and manages the team of expert writers on this site. He believes that educating homeowners about HVAC systems is one of the most impactful aspects of his job.