Tankless Water Heater With Hard Water

Tankless Water Heater With Hard Water

Tankless Water Heater With Hard Water

long-term movement of hard water through a pipe can result in what is called scale buildup (1). Just as in the human body where blood vessels can be reduced in inside diameter due to cholesterol buildup, water pipes can gradually close up resulting in less water movement through the pipe and a lowering of water pressure.

Hard water can wreak havoc on all your water-using appliances, so if you know you have it, you can be fairly certain it’s affecting the efficiency of your water heater. Hard water contains a number of minerals, most commonly calcium and magnesium. These minerals can build up over time, especially in appliances that use hot water, as heating the water separates the minerals and causes them to settle or form scaly deposits around heating elements. Over time, this buildup can lower a water heater’s capacity by reducing the amount of space for water inside the tank. Buildup also impacts efficiency because it collects near the heating elements and makes heating cycles take longer.

If we all showered with rain water — which contains almost no limestone content — there would be no need for water softening and conditioning products. 

While you may not be able to change the hardness of the water coming into your home, you can perform a few interventions that can help restore your water heater back to its original condition.

A tankless water heater will develop a build-up called limescale that will negatively impact the unit’s efficiency by creating a layer of “insulation” between the heat exchanger and the water it is trying to heat. Eventually, it could cause the tankless unit to throw error codes or shut down all together.

Water hardness varies by geographical location, and the level of hardness is determined by the amount of dissolved minerals within the water supply. 

If you have noticed a film on your bathtub or shower, you most likely have hard water. Also, hard water limits the sudsing and cleaning capabilities of many detergents and soap.

When hard water is heated, it causes the particles to suspend in the water. They attracted to each other causing them to stick together. When these particles stick together, they become heaver than water and sink.

The real problem of hard water is for devices with a tank. Nevertheless, the case of a tankless water heater with hard water also requires our attention as they do not enjoy of any immunity to the buildup of limescale.

However, the effects on tankless water heaters are minimal and time delayed. As water moves through the heat exchanger, the minerals will drop out of suspension, but most of the minerals will be cleared out with the water flushing through. Thus the build up of scale takes a longer time.

All tankless water heaters, even traditional tank-style water heaters, should have a sediment filter installed to filter the incoming water. It’s important to remember that whatever method you choose to reduce your hard water issues, you’ll still need to perform regular maintenance and flushing on your hot water heating system.

If you live in an area that’s prone to hard water, you may want to consider installing a whole house water softener, as these systems will not only protect your tankless unit, but also your other appliances, faucets and plumbing.

Our favorite hard water system is the scale inhibitor, however you should take a close look at each and make the best decision for your individual situation, especially if hard water is a concern in your area.

Be sure to hire a reputable company if you don’t plan on doing the work yourself. Keep in mind that there are many different options available to treat hard water. You should be able to find a method that best meets your situation and budget. 

Tank vs Tankless Water Heater With Hard Water

In a tank, the limescale, accumulates at the bottom and does not affect the flow of water.

Instead, the tankless water heater has small inlets and outlets to move water through its heat exchanger whenever a tap comes on. It doesn’t take much limescale build up to block these intakes

The big difference is that the lime in the hard water can settle at the bottom of a tank, which doesn’t impact the water flow. However, it can really affect how a tankless water heater works.

So, is it ok to use a tankless water heater with hard water?

The answer is yes. There is no reason that you can’t use one even if you have a lot of lime or calcium in your water supply.

When you do the math, tankless water heaters are a better investment for your budget and your planet. Conditions that affect the longevity of your tankless water heater include:

  • Water Quality – Hard water is exactly that: tough on appliances and plumbing systems throughout your home or office. It can reduce a water heater’s lifespan by 2 or more years!
  • Location – Water heaters located in garages or crawl spaces have to work harder to heat the water.

How Long Can I Expect An Electric Tankless Water Heater To Last With Very Hard Water ?

Homeowners can expect an electric tankless water heater to last a US average of 11 years with a hardness level of 15 GPG, recorded for Indianapolis very hard water, and without the utilization of a softener or filtration system.

Therefore, it is advised for homeowners to utilize filtration or softener devices in their tankless water heater with hard water to improve the duration of the aforementioned device to the standard average of about twenty years.

What Is Hard Water?

Hard water is simply water with a high mineral content. As water travels through the ground, it dissolves minerals like limestone and chalk. Since those are very soft and easily dissolved, most people with hard water find that it contains either a lot of lime or calcium.

The level of “hardness” in water is determined by the amount of dissolved minerals within the water supply. Different geographical areas are prone to different levels of water hardness. Rain water is called soft water because it’s relatively pure and mineral free.

The rain water is absorbed into the ground and travels to rivers and other bodies of water. Along the journey the soft rain water passes through soil and rock and begins to change to hard water as the minerals from the ground are dissolved into the water.

A lot of the water we use comes into contact with underground limestone, which is rich in minerals like calcium and magnesium. When the water contains 10 or more grains of these minerals, it’s considered “hard” — and when there are fewer than 3 grains, it’s considered “soft water.”

The technical description of hard water is based on the number of grains of hardness per gallon of water. OK so what is a grain? Well a grain of hardness is the amount of magnesium and calcium equal to the weight of a kernel of wheat. What is all translates to is

  • Less than 1.0 = Soft
  • 1.0 – 3.5 = Slight Hardness
  • 3.5 – 7.0 = Moderately Hard
  • 7.0 – 10 = Hard
  • 10.0 and Over = Very Hard Water

Very hard water can be a problem for tankless water heaters too.  A buildup of sediment can reduce the GPM (gallons per minute of water passing through a fixture) you’re getting  and eventually damage the unit.  Read more on the importance of flow rate . Tankless water heater manufacturers like Navien, Titan, Rheem recommend that homes with a hardness of 11 grains per gallon (GPG) use a water softener to treat water before it enters the unit.  The 11 GPG amounts to roughly 210 parts per million (PPM) total dissolved solids, and we mention that because some tests give results in GPG while others give them in PPM.

The problem with hard water is that calcium will precipitate out in hot water, collecting in aerators, washing machine filters, appliance pre-filters and within the water system of appliances.  This can be a serious problem for appliances that use water, as sediment accumulates in water intakes and pumps, making it hard to get the water it needs or eventually causing mechanical failure.

There are several ways to test the water’s hardness in your area. Some laboratories use the parts-per-million method, while others use the grain-per-gallon method, which dates back to ancient Egypt and is the equivalent of one dry grain of wheat. There’s an easy way to correlate this data. If the water has been tested at parts-permillion (or milligrams-per-liter), just divide by 17 to get the hardness in grains-per-gallon. For example, water that has scale at 200 parts per million has approximately 11.7 grains of hard minerals.

Hard water can be damaging to a home’s pipes and appliances, as we’ll discuss in detail below. And here’s the bad news: Roughly 85% of the U.S. has hard water, according to Homewater101. If you don’t live in New England, the Pacific Northwest or sections of the Southeast, chances are high that your water is hard.

The upper Midwest has America’s hardest water, but there are many other locations where it’s a problem, including San Antonio, Miami, Phoenix and Las Vegas. By some estimates, however, only about 30% of homes with hard water currently use any water softening products.

Hard water contains a high concentration of natural minerals particulary calcium carbonate and magnesium. These minerals are not a health concern, but they do cause problems for many home appliances.

Accumulation Of Limescale Particles In Water Heaters

Limecale formation can affect negatively different type of appliances. However here we will only concentrate on the limescale affecting a tankless water heater with hard water.

When mineral laden hard water enters our homes, a scaly build-up begins to form as some of the minerals attach to the surfaces that come in contact with the water. Over time, the build-up of minerals becomes a hard and scaly layer called limescale.

Limescale is created when hard water gets heated. The calcium and magnesium separate from the water and take solid form. Much like the plaque that forms in our arteries, too much scale build up can do real damage to the water “circulatory system” as it flows through pipes, shower heads and home appliances. This limescale can accumulate inside your pipes, water heater, washing machine and dishwasher, which can lead to other issues and even failure of certain appliances.

Scale buildup can reduce the efficiency — and even shorten the lifespan — of many items in a home. Tankless water heaters are particularly sensitive to hard water, but so are dishwashers, ice-makers and washing machines. Even when attempts are made to de-scale these appliances, they sometimes never return to peak efficiency.

Scale from the minerals will build up along the interior of the tank no matter what, but the heat in the tank speeds up the process of dissolving the minerals into limescale. The scale along the inside of the tank creates an insulating layer, making it harder for heat to escape from the tank. That’s not good news—because it means the tank will eventually overheat. That spikes pressure in the tank, causes leaks, damages the pressure expansion tank, and takes years off the life of the water heater.

Hard water also leaves a sediment layer across the bottom of the tank. This lowers the efficiency of the water heater and can cause bills to skyrocket. Although flushing the tank removes this sediment, it still isn’t something you want happening all the time.

Heat exchangers in tankless water heaters are extremely vulnerable to even the smallest amount of limescale buildup. Over time, the exchanger must work harder to transfer heat, dramatically reducing its overall efficiency and even cause it to overheat. Hard water can also cost a household in other ways. When hard water levels are high, it usually takes more laundry detergent to wash clothes and more soap and shampoo to adequately lather. It also takes longer and more elbow grease to clean.

Limescale build-up causes a tankless water heater’s heat exchanger to work harder than it should in order to bring the cool water entering the unit to the desired hot temperature.

Eventually, the heat exchanger will overheat due to the increased workload. In many cases, an error code is triggered and the unit will be automatically shut down. Service and/or repair may be required to get the tankless water heater operating again.

Limescale Development Consequences In A Tankless Water Heater With Hard Water

  • The heat exchanger will need to work harder to heat water because its caked with limescale. It will eventually overheat.
  • The heat exchanger will not reach it’s service life potential and need to be replaced.
  • An error code could be triggered to shutdown the unit. A professional plumber may need to be called to get the unit up and running again.
  • As limescale build-up increases, the heat exchanger’s burner cycles also increase in order to compensate for the lost efficiency. When this happens, the tankless is no longer saving you money on your fuel bills because of its lack of efficiency.
  • Manufacturer warranties do not cover damage caused by limescale build-up.

Detecting If you Live In A Region With Hard Water

One surefire way to determine if you have hard water you have probably been seeing for years already. Does your soap lather up well or do you end up with soap scum all over your bath and shower doors?

Then you probably have hard water, but it is still worth it to investigate further.

This map from the USGS is pretty handy. Take a look and see if you live in an area that generally has hard water. If you are in a hot spot, then you probably don’t even need to do a test. It is highly likely you are experiencing hard water and will need to take that into consideration when you buy a tankless water heater.

The most accurate way to know for sure is to get your water tested. You can get a cheap one off of Amazon, that also checks pH levels and chlorine among other things. The best part is it works in seconds.

It is definitely worth it to find out how hard your water is as it will impact which type of tankless water heater you get and if you need a water softener or not.

The amount of scale in your water is measured in grains. We’ll get more into what that means in a bit, but keep that word in mind for later.

Prevent Having A Tankless Water Heater With Hard Water With These Quick Actions

Hard water will take years of service life from your faucets, dishwasher, washing machine and even your toilet! The effects of hard water can be problematic for all water heaters, not just tankless models.

When it comes to tankless water heaters, it can seriously limit its effectiveness and also shorten the lifespan of the unit.

You’ll essentially negate any of the savings off of your gas or electric bill if your on demand water heater has been affected by the hard water as it will strain to keep up with demand. This means it will use more gas or electricity to work.

You’ll be taking years off of your tankless water heater which also ends up costing you more in the long run.

One of the best features of having one is the long lifespan. If you’re shaving years off of its life then again, you’ve taken away one of its biggest advantages.

In some cases, your on demand water heater won’t even work once the lime or calcium accumulates too much. You’ll get an error code and your unit will shut itself off.

Flushing The Water Heater To Avoid The Formation Of Limescale

To avoid that the limescale accumulates on the surface of the heat exchanger, we have to perform a flushing of the water heater, frequently.

Flushing your water heater involves completely draining the tank so that minerals suspended in the water or loose scales built up around heating elements are swept out. Some methods of flushing also include keeping the cold water valve open so the water coursing through loosens more buildup.

You can perform a water heater flush on your own. Opening a spigot and valves that get little use can be risky, as these components can break or fail depending on their condition. Also, the water coming out of the tank is extremely hot, and a misstep could cause injury.

Flushing a tankless water heater is critical to keeping it operating at it’s peak performance, and to help it reach it’s service life potential. Regular flushing is especially important if you live in an area with hard water. 

Manufacturer recommendations vary, but most suggest flushing your unit every 12 months. Although, keep in mind that, in the end, the frequency should be based on the area’s water hardness. 

Although limescale can be removed from your tankless water heater by regular flushing, the best solution is to prevent it from forming in the first place. Being pro-active can greatly reduce the affects of hard water.

Let´s see other options, that are much more proactive than allowing some sediments of limescale to accumulate, right below.

Lower The Temperature

The hotter the water, the faster the minerals in hard water build up because the minerals are more easily separated at higher temperatures. Manufacturers typically recommend setting your temperature to 120F, which is the maximum recommendation if you have hard water. If you’re comfortable setting the temperature a little lower, that’s even better. Changing the temperature won’t stop hard water buildup, but it will slow it down.

Quick Hard Water Test

We highly recommend purchasing an inexpensive hard water test kit from Amazon so you can test your water yourself and know the hardness of your water. These types of test kits deliver results in only a few seconds.

These tests, called test strips will allow you to determine the mineral content as well.

A DYI Quick Hard Water Test

  • Take a empty plastic pop or water bottle with cap. 16 ounce or bigger. (make sure it is rinsed clean)
  • Add 8 to 10 ounces of luke warm tap water
  • add about 10 drops of your home dishwasher liquid
  • Put cap back on the bottle and shake the bottle for about 15  seconds
  • If the soapy liquid foams up quickly and leaves a nice foam in the top of the bottle you have good not hard water
  • If instead the water turns cloudy with a soapy film on the sides of the bottle rather then foam you most likely have hard water.

Scale Inhibitor Systems

A scale inhibitor system is a relatively inexpensive way to protect water heaters from hard water. This system allows water to pass through a filter before it enters the water heater.  To make changing the filter easy, a shut off valve should be installed on the pipe on each side of the filter.

The product protects tankless water heaters without chemicals or requiring electricity and works better and longer than de-scaling. As water flows through the filter, hard-water minerals form inactive scale crystals that travel through the tankless unit without sticking to the heat exchanger. This technology eliminates the need to use isolation valves to flush the tankless unit with a de-scaling solution. All the service technician needs to do is replace a cartridge in the filter every two years. 

Flushing both traditional tank-style and tankless water heaters will help remove the limescale build-up after it has already developed. However, installing a Scale Inhibitor System can help reduce the limescale build-up from forming in the first place. 

A Scale Inhibitor System, such as the 3M Aqua Pure, is a popular and relatively inexpensive method of protecting traditional tank-style and tankless water heaters from hard water. The filter is installed on the incoming water supply BEFORE it enters the water heater. This type of filtration system reduces limescale build-up by preventing minerals from bonding to the metal surfaces.

A shut off valve should be added to the pipe on each side of the filter to allow for the ease of filter replacement. 

The incoming water travels through the Scale Inhibitor System where it’s treated with polyphosphates which help inhibit scale build-up within your water heater. 

Installation Of A Water Softener

The best way to extend the life of your water heater regardless if it’s a conventional water heater or tankless water heater is to install a water softener. A water softener will make you tap water taste better, can extend the life of your water heater and in some cases stop your clothes from getting a yellowish tint them.

If your hardness level is below 8 grains per gallon, then you don’t really need the water softener. Though I recommend one as it is a good investment to preserve the condition of your other appliances like a dishwasher or washing machine.

If you don’t want to bother with that, then you will need to flush your tankless water heater.

Otherwise, you will need to do it once per year to be on the safe side. Even a slight layer of build up can reduce your tankless water heater efficiency by up to 30%. This totally negates the efficiency that you gained by switching to a tankless in the first place.

You may get a couple of years without descaling your unit, but if you start to see your gas or electric bills increasing, it may be an indication that you have some build up and it is straining the heat exchanger.

Scale deposits that form in a heat exchanger (or on electric heating elements) slow down heat transfer and constrict water flow. Scale won’t be an issue if you already have whole-house water-softening. But if your water isn’t being softened, and its hardness exceeds 120 milligrams per liter, then it’s worth investing in a treatment system.

A water softener is a mechanical device which is you, or a plumber can install inline with your main water supply. All softeners work with the concept of removing minerals with sodium. Don’t worry about the sodium; it only traces amounts. The chemical process is called ion exchange.

A softener holds a small amount polystyrene beads and salt. The beads have a negative charge. Both calcium and magnesium have a positive charge. When the incoming water passes through the polystyrene beads, the calcium and magnesium cling to the beads. After a few cycles, the beads become saturated with calcium and will no longer attract more calcium. To solve this issue, the unit does a regeneration cycle where the beads are soaked in sodium chloride solution. The soaking causes the calcium to lose it connection with the polystyrene beads, creating a brine. The brine is then flushed through a drainpipe, and the process starts all over.

A whole-house water softener removes hard water minerals as water enters the home from a well or public source. Because this happens upstream of your water heater, hard water minerals have already been removed by the time the water reaches the tank. No minerals, no buildup.

Both salt based and salt-free water softeners are a good fit for areas with extreme hard water. All of the incoming water to the house is treated, both hot and cold, so all of your appliances, fixtures and plumbing will benefit.

Space-saving, slim-profile water softening units now include self-cleaning sediment filters, power-loss protection and touchscreen controllers.These are typically available in 35,000 to 50,000 grain capacities. The 35,000-grain product is ideal for a two to four person household, while larger families would probably need the 50,000- grain unit. In addition to reducing scale buildup, these units help prevent water stains and spots — and can improve skin and hair softness. Another great selling point: These units never require a filter change.

These systems treat all of the water, both cold and hot that enters your home.

Types Of Water Softeners

There are 2 main types of water softeners:

  1. Salt Based
  2. Salt Free

Each works differently, and each has advantages and disadvantages. Let’s take a closer look at each:

Salt Based Water Softeners

Salt based water softeners are often the most affordable way to treat water. These systems completely remove the calcium and magnesium from the water before it enters your plumbing system.

The hard water minerals are replaced with sodium ions, by binding negatively charged potassium, sodium or hydrogen resin to positively charged metal ions. The process draws the hard minerals from the water. In other words, as hard water enters your water softener it runs through resin beads which attracts and traps the “hard mineral” molecules. The water that enters your home is left mineral free. 

Over time, the resin beads become “full” of the hard water minerals and a process called regeneration needs to occur to keep your water softener working effectively. 

Salt Free Water Softeners

Salt Free Water Softeners work very differently and are commonly called water conditioners or scale inhibitors because the hard water minerals are not removed from the water. Although, salt free water softeners don’t reduce the hard water minerals, they will help prevent the build-up of lime scale. There are 2 common types of salt free systems: Catalytic and electromagnetic.

Catalytic Systems

These systems use a process called epitaxial crystallization. In theory, the calcium is changed from the type that deposits limescale (calcite) to a type that doesn’t (aragonite).

The hard water mineral ions are bonded to a chelating agent that suspends them within the water. In other words, the minerals are not removed, but pass thru the water and are stabilized making them unable to cause limescale. 

Electromagnetic Systems

With an electromagnetic system, the ions of the hard water minerals are altered as the water passes through a magnetic field. These systems are very easy to install and many people like that there are no chemicals used in the water treatment process. However, there is some debate on their effectiveness. 

The Eddy Water Descaler is an example of an electromagnetic salt free water softener. This system is easy to install and can be used with both metal and plastic pipes.

Regeneration Cycle In Water Softeners

Almost all residential water softeners use the combination of beads and salt to remove hard water elements. The biggest difference is on how and when the regeneration cycle is activated.

Electronic Timer: A timer causes the cycle to run at set intervals. The unit can not supply soft water when while recharging.

Computerized: Most of these units have a reserve resin, which means you can get soft water while the unit is recharging.

Mechanical Systems: These units have 2 tanks and are much larger. One tank recharges while the other tank makes soft water. These are the most versatile of the units.

Perform A Yearly Maintenance

Most tankless water heaters require a yearly maintenance. The primary purpose of this maintenance is to flush the unit of any scale build up. A vinegar-like solution is run through the unit to clean out any scale build up. The time between cleanings depends on how hard your water is and how much the unit is used. The general guideline is once a year for maintenance.

Whether your water heater is tankless or tank-style, dealing with the affects of hard water requires a proactive approach. The methods shown above can help protect your water heater from limescale, and regular flushing will remove any limescale that has formed. 

Acid Neutralizer For A Tankless Water Heater With Hard Water

Acid neutralizers for tankless water heaters help neutralize acidic condensation and prevent premature deterioration of pipes and other materials.

Point Of Use Cartridge

 A dedicated, point-of-use cartridge like the TAC-ler water conditioner (Stiebel Eltron) alters hardness without adding salt or other chemicals.

Installation Of An Isolation Valve

If you live in an area with hard water, then you should definitely make sure you install an isolation valve on your unit if it doesn’t already have them. This will make it very easy to do the deliming without needing a plumber.

Installation Requirements For A Tankless Water Heater With Hard Water

For the installation of a tankless water heater with hard water in the system, we have to undertake some actions before, apart from the ones I analyze in this article.

You should run your municipal water through a softener. Without a softener, your heater would probably soon quit working as the water feed will become plugged with minerals.

The degree of scaling that occurs in potable hot-water systems is dependent on the type of hardness, the temperature rise, and changes in pressure. The hotter the delivery temps, the greater the amount of scaling. For example, tankless water heaters targeting 120°F are less susceptible to scaling than tankless water heaters set for 140°F, and so on.

Most of the precipitated minerals in tankless water heaters are flushed through the system because of the high velocity of the water zipping through the heat exchanger. However, tankless water heaters should be installed so that the heat exchanger can be chemically cleaned. Isolation valves and boiler drains easily solve this issue, and several manufacturers, as well as third-party vendors, have flush kits. Noritz and a few others have in-line filters they claim allow their tankless water heaters to be used in hard-water conditions.

Tankless water heaters have sensors that monitor the heat-exchanger operation, and scaling inside the heat exchanger’s tubing will act as an insulator, which will eventually lead to a fault code for over-temperature conditions. Once that occurs, a thorough chemical flush will need to be done before the unit can be placed back into service. Because of the personal and property safety issues involved, this work is best handled by licensed professionals trained in the procedure.

Hard water is typically made up of calcium, magnesium, bicarbonates, and sulfates. A lab can provide details of what’s in the water. Water hardness is expressed in grains; water measuring over 4 grains is typically considered the threshold for using a water softener.

Before running hard water through a tankless heater:

  • Have the piping set up to facilitate chemical cleaning.
  • Install a prefilter designed to mitigate the hardness.
  • Have your installer check the inlet water pressure while operating the heater under full-flow conditions, and measure the delivery GPM flow rate (timed delivery into a bucket with gallon marks). This sets a benchmark for the new, clean heat exchanger, and provided that the inlet pressure is the same for subsequent tests, the full-flow outlet GPM test will reveal if any scaling has created a buildup within the heat exchanger.

Best Tankless Water Heater With Hard Water

It doesn’t matter which tankless water heater brand or model you buy when you have hard water. They all will need to be flushed. The best ones, however, will alert you to when they have accumulated lime or calcium and need to be descaled.

But the ones I recommend that have an alert, will inform you when to flush, when the accumulation of foreign substances occurs, that is all what can distinguish the best tankless water heater with hard water.

How often will you need to flush it? That depends. If you get one that I linked to before, you will get an alert when the scale is starting to build up.

There are many brands, but I can only describe a few of them that I know below. Let´s visit the best tankless water heater with hard water.

As the scale builds up (more extended period of time) it will cause the heat exchanger to overheat. We believe every current tankless water heater on the market has a safety shut off when a heat exchanger overheats. This prevents damage to the unit and safety to the homeowner. If the unit is reset without the problem being corrected, it will only function for a very short time before the unit shuts itself down.

Some manufacturers such as Rinnai has built in scale detection, which will alert the homeowner on when the unit needs to be flushed. The scale detection for Rinnai is only available on their Ultra and Luxury series.

The best way to prevent hard water is to have your water treated with a water softener. This not only helps your tankless water heater, but it also helps increase the longevity of your plumbing system.

Stiebel Eltron Tempra 24 Plus Electric Tankless

Stiebel Eltron has a large line of tankless water heaters. The Tempra 24 Plus may be the mid-sized unit in the line-up, but it’s more than capable of delivering plenty of hot water to your household. With 24kW’s, the Tempra 24 Plus can deliver a flow rate of 3.64 gpm with an incoming water temperature of 45°.

With it’s sleek good looks and superior German engineering, Stiebel Eltron is an excellent choice. The Advanced Flow Control means you won’t need to worry about running out of hot water when demand is higher than expected. 

There’s no need to hide this water heater in the basement, not only does it look good, but it runs virtually silent. And since it doesn’t need to be vented, it can be installed nearly anywhere!


  • Uses the German patented Advanced Flow Control, which automatically reduces the flow of hot water in order to maintain the temperature when the demand exceeds the system’s capacity. 
  • Solid copper heating modules.
  • Pre-set temperature memory buttons and a digital display that monitors the temperature and usage of the unit.


  • Quality comes at a price. Although less expensive than a gas tankless water heater, the Tempra 24 Plus is on the higher-end of the price scale for an electric tankless water heater.


  • Flow Rate @ 45°F Rise: 3.64 gpm
  • Fuel: Electric
  • kW: 24 kW
  • Installation Location: Indoor
  • Warranty: 7-year heat exchanger

Rheem RTEX-24 Electric Tankless

The Rheem RTEX-24 is an excellent choice if your looking for a whole house electric tankless water heater. It’s capable of delivering a flow rate up to 5.9 gpm, but if you need a more powerful unit, there are plenty of others in the RTEX to choose between.

Rheem is a top-notch brand, and their RTEX line-up is a favorite among consumers and professionals. Although the RTEX-24 is capable of servicing up to 3 showers running simultaneously, proper sizing is critical to your geographic area. If you purchase a unit too small, you’ll most definitely be unhappy.

You’ll have plenty of installation options with the RTEX-24. It doesn’t require venting so it can be installed nearly anywhere. The sharp, clean lines and classy finish means you don’t need to tuck the unit out-of-sight. This is an excellent choice, and with proper maintenance, it’ll last a very long time.


  • The electronic temperature control is easy to read and allows the unit to make 1° adjustments. Temperature settings can be made between 80 to 140°F.
  • Three Copper immersion heating elements are not only durable, but are threaded with a brass top for easy replacement. 
  • Advanced self-modulation system can deliver 99.8% energy efficiency because it adjusts the power up or down to meet the hot water demand. 


  • Professional installation is recommended. Although, this is an additional expense, electric tankless water heaters are easy to install and having it done by a professional will give you peace of mind that its done correctly.


  • Flow Rate @ 45°F Rise: 3.64 gpm
  • Fuel: Electric
  • kW: 24 kW
  • Installation Location: Indoor
  • Warranty: 5-year heat exchanger

Rinnai RUR199iN Gas Tankless

The Rinnai RUR199iN is a powerful gas tankless water heater. It has all the bells-and-whistles you’d expect from a premium brand and it’s capable of delivering up to 11 gpm of hot water. It’s also the direct and updated replacement for the RUR98iN model.

It’s hard to go wrong with a Rinnai and the RUR199iN is an excellent choice. With one hundred years of experience behind the company, and one of the best warranty’s in the industry, Rinnai has earned a reputation of being the best of the best. In fact, the average service life of a Rinnai is 20-years!

If a part needs to be replaced, it can easily be swapped out with a new part. No need to purchase a whole new heating system. Although professional installation is strongly encouraged, that is the norm for all tankless water heaters. The RUR199iN has multiple venting options and does not require expensive Category III material, making installation easy for a professional.


  • This unit is ideal for homes without a dedicated return line. The ThermaCirc360 technology means you’ll have hot water fast due to the built-in recirculation pump, timer and thermal bypass valve.
  • The Uniform Energy Factor of .93 means nearly all of the energy used is going to heat your water. This is a very high score for a gas tankless and one of the reasons this heater is ENERGY STAR certified.
  • The included Control-R Module allows you to control the RUR199iN from an app on your phone. Adjust the temperature, activate recirculation,  and even allow for remote monitoring with a professional for maintenance or troubleshooting. With Control-R you’ll be able to control your tankless even if you’re on vacation!


  • The RUR199iN is a premium tankless water heater, but it’s not inexpensive. It’ll definitely add to the resale value of your home, but if you’re planning on moving soon, it may not be worth the investment.
  • Professional installation is recommended, and if your a DIY kind of person, keep in mind that improper installation may void your warranty.


  • Flow Rate @ 45°F Rise: 8.5 gpm
  • Fuel: Natural Gas
  • BTUs: 199,000
  • Installation Location: Indoor
  • Warranty: 15-year heat exchanger

Titan N-160 Tankless Water Heater With Hard Water

While it is not better to handle hard water than the Rinnai, it is the best tankless water heater overall according to our readers. We have a complete review of that recommended model in this article, here.

Gas Water Heaters with a Tank

In a conventional gas-fueled tank water heater, the heating element (the burner) is at the bottom of the storage tank. The water heats up, and the particles sink, and the process repeats itself over and over.  Over time, the lower part of the tank fills up with particles, the particles act as an insulator and cause the burner to be less efficient. In extreme cases, the burner will have to run so long that the steel becomes overheated causing the tank to leak. This can lead to the dreaded “tank rupture” which cause 40-60 gallons of water to flood your basement.

Electric Water heaters with a Tank

Electric tank water heaters are less prone to tank rupture because the heating elements are suspended in the top and middle of the storage reservoir. While most of the calcium will sink to the bottom, some of it will become attached to the heating elements, shortening the lifespan of the water heater.

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BY M. Kogan

Hello, I am Marcio. I am an architect and designer, alma mater is Mackenzie. Retired in theory, but an architect never retires completely. Along with architectural projects, I am a filmmaker and have completed some short documentaries. Filmmaking and design are my passions. In HomeQN I write about home decoration and foundations. The goal is to teach homeowners to DYI as much as possible, and when this is not possible, enable them through knowledge, to evaluate service quotations and choose the best service technicians.

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