Best Rheem Tankless Water Heaters Review

Buyers Guide, Tankless Water Heater

Best Rheem Tankless Water Heater
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Table of Contents

Are you on the lookout for an unbiased review of the Rheem Tankless Water Heater?

Well, in this post, I would be walking you through some of the best Rheem tankless water heaters available on the market.

Moreover, I would be throwing light on the “must-have” parameters in the “buying section” in order to help you make an informed buying decision.

Lastly, I would be responding to the queries related to the Rheem tankless review to help you clear your doubts.

But, before that, I would be needing a small help on your end.

Are you willing to help me?

If your answer is “YES”, then all you need to do is to answer a couple of questions that I would be asking in a while.

Does it make sense?

So, which is your favorite tankless water heater brand?

How much are you willing to spend on your favorite Rheem tankless water heater?

Would you prefer buying a Rheem electric tankless water heater or a Rheem gas tankless water heater?

Enough of questions, right?

So, without any further, let’s begin…

Rheem was founded way back in 1925 by the Richard and Donald brothers and is headquartered in Emeryville, CA.

Needless to say, the brand is known for its high-quality, reliable, and most importantly affordable product line.

Currently, Rheem is mainly manufacturing products related to heating, cooling, water heating, pool & spa heating, and commercial refrigeration.

The brand RHEEM is successfully expediting the operation for over 100 years now.

Many of you might not be aware of the fact that Rheem is one of the largest manufacturers of water heating products in North America.

Which is the best Rheem electric tankless water heater for the money?

To be honest, all the Rheem electric tankless water heaters that made our list are of high quality and worth the investment.

However, if you’re interested in knowing my top pick, then I would be more than happy to share it with you.

Rheem RTEX-18 18kW 240V Electric Tankless Water Heater

So, here I come with my favorite Rheem electric tankless water heater, and there are numerous reasons for it.

Frankly speaking, the Rheem RTEX-18 comprises almost all the essential features that you might be looking for in your electric tankless water heater.

Not only that but also the unit is equipped with innovative and advanced technology including self-modulation.

The benefit of highly advanced modulating technology is that adjusts the power to meet the hot water demand so the chances of underutilized power become less.

Furthermore, the manufacturer claims to provide a water flow rate up to 4.4 GPM so you can definitely run a couple of showers simultaneously in a warmer climate.

However, in the extremely cold climatic conditions, the input underground water temperature would be quite less so you’ll have to compromise a little bit on the GPM, and the same holds true with any other tankless water heater model.

In order to help users with better control over the device, the manufacturer has inculcated digital thermostatic control along with an LED display.

Installation is simple, easy, and less costly as compared to a gas tankless water heater because you wouldn’t be needing venting, etc.

Nevertheless, the installation might require electrical, plumbing, and overall water pressure adjustment.

While expediting the installation process make sure to use the suggested 8 AWG wire for dual 40 Amp circuit breakers.

Furthermore, you need to ensure that all the faucets are opened before powering the unit else you might get an error code on the unit.

And, if you’re migrating from a traditional water heater to this little beast, then I can assure you that there would be a tangible reduction in your electricity bills for sure.

Nonetheless, sizing is very important whenever you’re planning to buy any tankless water heater.

In case, you’re not sure about the tankless heater size that would suffice your needs, then my advice would be to call the Rheem representative for the way forward.

I’ve been using the Rheem RTEX-18 quite a few times now, and I can affirm that it doesn’t take more than 120 seconds for hot water to reach the farthest bathroom.

On the downside, the unit might not be a great fit for your home if there are 100 or fewer amps of electric service coming to your home.

All in all, the Rheem electric tankless hot water heater is a great product and you’ll never REGRET investing in it.

I might sound crazy and biased about this idiosyncratic superlative tankless heater but it’s the fact and I’m not exaggerating anything.

[Related] Rheem RTEX-18 Review

Which is the best Rheem alternative tankless water heater for the money?

So, here I come with my favorite tankless water heater that could be a great substitute for the high-quality Rheem tankless.

However, I would like to affirm that all the natural gas tankless heaters that made it to our list are of high-quality and worth the investment.

Rinnai RU199iN Tankless Water Heater

The Rinnai RU199iN is a tankless water heater that uses natural gas as a fuel.

It comes with a huge capacity and is capable of providing endless hot water to your entire home effortlessly.

In fact, the Rinnai RU199iN is capable of providing a hot water flow rate of up to 11 GPM.

On top of it, the unit is equipped with advanced technologies including Circ-Logic that allow you to set recirculation patterns.

And, as a result, you don’t wait long for hot water rather you get it instantly.

The RU199iN is small, compact, and uniquely designed so you can install it in tiny spaces including non-traditional ones such as an attic, closet, etc.

Furthermore, the design of the unit plays a crucial role in reducing co2 emissions, use less energy, and conserve water.

The vertically integrated unit comes with a life expectancy of 20 years which is almost twice that of a tank-styled hot water heater.

In case of malfunctioning or discrepancies, you don’t have to replace the entire unit rather you can swap the Rinnai tankless water heater components.

In layman’s terms, if you’re looking for a Rinnai tankless for you running a couple of showers, dishwasher, faucet simultaneously, then definitely, the Rinnai RU199iN could be a great fit.

In order, to free your floor space, you can wall-mount the unit.

Lastly, the RU199iN is backed by 10 years warranty on the heat exchanger and 5 years on parts.

Which is the best Rheem natural gas tankless water heater for the money?

Frankly speaking, there are a couple of natural gas Rheem tankless heaters that would grab your eyeballs because of the idiosyncratic superlative features that they are equipped with.

Nonetheless, since I’ve to narrow down to one option only so I would bet high on RHEEM RTGH-84DVLN-2.

RHEEM RTGH-84DVLN-2 Natural Gas Condensing Tankless Water Heater

The RHEEM RTGH-84DVLN-2 uses natural gas as a fuel and is equipped with condensing technology that put this unit into a different league altogether.

Since the Rheem heater comprises a condensing technology so you can expect it to be highly energy-efficient as well as energy saving.

Like other premium residential tankless heaters, it also comes with a temperature setting that falls in the range of 98°F – 140°F.

Trust me, the unit is a real hulk as it comes with a GPM output rating of 40.

What actually it means is, you can run the dishwasher, clothes washer, sinks, and showers simultaneously without worry about the hot water requirement.

Well, some of my clients complained about the beeping noise, and let me tell you, how to get rid of such noises.

First of all, your Rheem tankless sounds such just because it isn’t able to get fresh air.

So, all you need to do is to take out the extra rubber grommets on the bottom of your Rheem tankless unit, and the beep sound will go away.

The aforementioned step has worked for a couple of my clients and I hope it will work for you as well.

Moreover, the unit is small and compact so you can easily install it in tiny spaces.

The unit can be easily installed similar to what you’ve found with other Rheem tankless units.

Of course, the review would be incomplete without mentioning the highly supportive customer support service of Rheem.

You can ask as many queries as you would want to, and the support team is there to help you out.

On the downside, service valves and plumbing aren’t included with the unit.

Which is the best Rheem propane tankless water heater for the money?

Honestly speaking, it would be unfair to say that one particular propane model of Rheem will overshadow all others.

Nonetheless, I’ve come up with my favorite Rheem propane tankless unit, and I hope it will suffice for your hot water requirements as well.

Rheem RTG-84XLP-1 Tankless Water Heater

The Rheem RTG-84XLP-1 uses liquid propane as a fuel and is designed for outdoor uses.

Moreover, the unit is equipped with an Ultra-Low NOx burner that not only ensures low emission but also safety measures.

For example, the Guardian Overheat Film Wrap prevents the unit from getting overheated and thus, prevents the damage that could result because of overheating.

The manufacturer has taken note of convenience, usability, and most importantly user experience which is clearly visible from the features that the unit is equipped with.

In fact, the Rheem tankless can be controlled remotely with the help of the remote control that it comes with.

Since no venting is required so expediting the installation process wouldn’t be a nightmare for even a first-time buyer.

Rest assured, the unit is capable enough to provide endless hot water for up to 3 bathrooms.

But at the same time, the manufacturer recommends professional installation to avail the warranty of 12 years on the heat exchanger and 5 years on parts.

The unit is only meant for outdoor uses and comes with freezing protection to up to minus 30 degrees.

On the downside, the unit doesn’t comprise a flush valve.

Which is the best Rheem residential tankless water heater for the money?

Well, if you’re looking for an affordable Rheem residential tankless water heater, then definitely, you’ve landed in the right place.

Not only does this unit performed extremely well in our evaluation process in the “affordable” category, but also has received some really positive feedback.

Rheem 240V Heating Chamber RTEX-13 Residential Tankless Water Heater

The Rheem RTEX-13 is perhaps the best residential tankless water heater that I’ve come across for small and mid-sized homes.

To be honest, it comprises almost all the essential ingredients that you might be looking for in your favorite residential tankless heater.

Be it the compact size, sleek design, efficiency, performance, user convenience, reliability, or whatever, the unit will not disappoint.

If your expectation is legitimate and not superficial, then I can assure you that most of it would be met by this little beast for sure.

However, if your hot water requirement is huge and very frequent, then this might not be the correct residential heater for you.

With a flow rate of up to 3.17 GPM, the unit can provide hot water to a couple of showers simultaneously in a warmer climate.

Like the aforementioned Rheem tankless heater models, it also comes with a smooth and hassle-free installation process.

In order to provide the end-users better control on the unit and easy temperature setting, the external adjustable digital thermostatic control with LED display.

The best part is, it allows you to adjust the temperature at an interval of 1 degree.

In order to reap maximum benefit out of this unit, my advice would be to use water saver showerheads.

I’ve been personally using these showerheads and would recommend them to all the avid readers out there.

The RTEX-13 boasts about being 99.8% energy efficient.

You can install it in tiny spaces, as well as, wall mount it in order to free the floor space.

Again, I’m repeating it, the unit is small and would be able to cater to the hot water requirements of a single bathroom only.

The only downside that I find with this electric tankless heater is that it is not “star energy” certified so you’ll not be able to reap the benefit of a “green” rebate.

All in all, a mind-boggling offering from the brand RHEEM in the affordable category, that will definitely match up to your expectation in case, you’re using it for a single bathroom.

Best Rheem Tankless Water Heater Review

Well, before we dive deep into the discussion, please allow us to explain our evaluation process.

Stay calm, we’re not gonna take much of your time, indeed!.

First and foremost, our team of experts does the brainstorming and comes up with a set of parameters on which the products need to be evaluated.

In this case, the product is Rheem tankless hot water heaters.

Each evaluation parameter is assigned a certain weightage depending upon its ability to influence a buyer’s decision.

During the evaluation, each product scores certain marks across the parameters depending upon one’s performance.

Finally, we sum up the score and shortlist the “top ten” scorers for our review.

However, if you still have any doubts or queries then you can reach out to us, and we would be more than happy to assist you.

Rheem RTEX-36 Residential Tankless Water Heater

The Rheem RTEX-36 Residential Tankless Water Heater is a powerful unit and comprises almost all the ingredients that you might be looking for in your favorite residential tankless water heater.

Moreover, the unit is small and compact so you can easily install it in tiny spaces.

The unit claims to provide a flow rate of up to 8 GPM which is in fact sufficient for a small to mid-sized home for sure.

On top of it, the Rheem RTEX-36 (240V) will provide 2.5 GPM at a 98 degree F temperature rise and 6 GPM at a 30 degree F temperature rise.

So, if you’re using the RTEX-36 in a warmer climate then it can easily suffice your hot water requirements of a shower, faucet, dishwasher, washing machine, etc.

Needless to say, the RTEX-36 is equipped with advance and innovative technology including modulating in order to help you achieve an optimum result by adjusting power to meet your hot water requirement.

The device is not only user-friendly but also highly flexible.

In fact, the RTEX-36 comprises a built-in digital thermostat control unit that gives you better control over the unit by increasing the temperature in an increment of 1-degree.

Whether you’re a seasoned professional or a newbie, the installation wouldn’t consume a lot of your time as well as it’s easy to expedite.

Just for your information, the unit is powerful and would be needing a 150 amp supply.

On the downside, some of my clients have complained about the inconsistent noise coming out of the device which might be a point of concern for you in case, your top priority is a noise-free tankless heater.

All in all, a great Rheem tankless water heater that you’ll not regret investing in for sure.

So, what are you waiting for?

Rheem 240V 3 Heating Chambers RTEX-27 Residential Tankless Water Heater

As compared to the previous model, the RTEX-27 comprises 3 heating chambers and is definitely worth the investment.

If you’ll dive deep into its idiosyncratic features, then you’ll get to know that the unit is highly suitable for homes that want to run a couple of showers and faucets simultaneously.

Like the RTEX-36, this little beast also comes with modulating technology and LED display along with digital thermostatic control.

It might not be as powerful as the RTEX-36 but is definitely powerful enough to cater to the needs of a small to mid-sized home with ease.

You can easily replace the damaged components of this unit so you don’t have to replace the entire unit in most cases.

Definitely, is energy-efficient and can be installed quickly and easily in tiny spaces because of its small, compact, and sleek structure.

In simple words, the RTEX-27 is a unique blend of flexibility, convenience, portability, and energy efficiency which is why it’s so popular among my clientele.

Trust me, you can easily run three showers simultaneously once you’ve installed the Rheem 27kw tankless hot water heater.

In fact, the 27kW tankless heater is capable enough to cater to the hot water needs of laundry, kitchen, bathroom, etc.

Just for your information, you need to install 240V in order to accommodate the 27kw tankless hot water heater.

Rheem RTG-84DVP Low Nox Direct Vent Tankless Water Heater

The Rheem RTG-84DVP is an environmentally friendly unit and meets low nitrogen oxide emission standards.

Moreover, the Rheem RTG-84DVLP is an indoor tankless water heater that could deal well with your hot water requirement without any hassle.

As compared to a conventional tank-style water heater, the RTG-84DVLP is small and compact, and wouldn’t require huge space for installation, indeed.

In fact, this little beast is almost one third-size of an average conventional heater.

Of course, the unit is energy-efficient and would definitely save you a tangible amount on electricity bills in the long run.

And, the best part is, the RTG-84DVLP is energy star certified.

Since it comes with UMC-117 remote control so you can easily operate it from remote locations.

With 180,000 BTU and a water flow rate of up to 8.4 GPM, the unit is bound to deliver high performance.

On the downside, some of my clients have complained about some minor issues such as limescale accumulation.

Nonetheless, you don’t have to worry at all as you can easily flush it off with the help of vinegar.

The unit is big enough to suffice your hot water requirements for a shower, dishwasher, and washing machine without any hassle.

Well, the installation could be a cakewalk if you’ve prior experience with propane tankless heater installation as well as plumbing.

However, if you’re buying an on-demand heater for the very first time, then all I can say is, take the help of a certified technician in order to prevent any last-hour misadventure.

Lastly, the 61.8 lbs RTG-84DVLP is backed by 12 years warranty on the heat exchanger and 5 years on parts which clearly shows the trust and confidence of the manufacturer in its offering.

Rheem Performance Platinum Natural Gas Indoor Tankless Water Heater

So, here I come with one of the most powerful Rheem tankless water heaters that I’ve got on my list.

Needless to say, it’s a premium offering from the brand Rheem, and will definitely, match your expectation if not EXCEED.

The only drawback that I see with this Rheem unit is its price.

So, my suggestion to the individuals on a shoestring budget would be to stay away from this idiosyncratic superlative product.

In simple words, the unit is well capable enough to provide you with hot water when you need it as well as how long you need it.

It goes without saying that the Rheem performance platinum tankless water heaters are one of its class, and can provide endless hot water to 3 bathrooms simultaneously at 35-degree temperature rise.

Not only that but also, the unit is environment friendly as it claims to save up to 1,100 gallons of water every year with the exclusive water-saving settings.

Of course, the unit is equipped with innovative and advanced technology including the condensing technology that makes this little beast highly energy efficient for sure.

In fact, the unit boasts about its energy-saving capability and claims to save up to 1,100 dollars over a time span of 12 years.

The installation process is easy, and less time-consuming as compared to its close competitors in the same category.

Frankly speaking, advanced venting technology increases the installation location options.

The unique and sleek design makes this small and compact unit to be installed in small spaces possible.

In fact, it can be wall-mounted, and thus, you can leverage the floor space for some other essential work.

Even though you’re running multiple faucets or showers simultaneously, you can expect the hot water coming out from the fixtures in less than 30 seconds which for me is really mind-boggling.

The Rheem performance platinum tankless water heaters are highly flexible and convenient to use as well.

In fact, you can add a pump to this heater to increase the speed of hot water.

But, I don’t think it would be needed until and unless your requirement is very specific.

It’s my humble request to all my readers if you’re a first-time buyer, then please refrain from installing the unit on your own.

It would be a good choice to hire an experienced technician for the installation purpose.

Lastly, the unit is energy star certified with a 0.93 UEF and thus, qualifies for quite a few rebates and incentives.

Rheem RTGH-95DVLN 9.5 GPM Indoor Direct Vent Tankless Natural Gas Water Heater

So, here I’m with yet another highly efficient and powerful Rheem tankless heater meant to deliver high-performance effortlessly.

It goes without saying that the unit is highly energy-efficient and is also equipped with stainless steel condensing heat exchanger in order to help you achieve the optimum result with ease.

On top of it, the Intelligent electronic controls design adds to both safety and energy efficiency.

The unit is a unique blend of both quality and reliability.

In order to provide the end-users with the best possible quality standards, the unit is tested not only by certified government officials but also by a third party.

Moreover, the RTGH-95DVLN can be easily installed in tiny spaces without any hassle, and the credit goes to the sleek and compact design that the unit possesses.

In order, to prevent overheating, the RTGH-95DVLN comes with an overheated film wrap.

Also, the unit is equipped with a digital display unit that not only shows temperature settings but also maintenance codes.

You don’t have to worry about cold climatic conditions as the unit is equipped with freeze protection up to minus 30 degrees Fahrenheit.

The unit is also equipped with a self-diagnostic system for easy installation and service.

I highly recommend this little beast for high altitudes, that is, up to 9,840 feet elevation above sea level.

Definitely, a high-quality Rheem tankless heater that you’ll not regret investing in.

Rheem Tankless Hot Water Heater Buying Guide

Well, so here I come with my favorite section wherein I’ll bring to your notice almost everything that I know about the product that I’m reviewing.

To be honest, I along with my core team have worked really hard to come up with this idiosyncratic superlative comprehensive guide to help you make an informed buying decision.

Choosing the Right Rheem Tankless Water Heater

Frankly speaking, choosing the right Rheem tankless water heater isn’t as easy as you think.

And, especially if you’re a newbie then you should be a little bit more cautious regarding the product features, sizing, and characteristics.

For example, a heater that is too small won’t adequately meet your mid-sized home’s hot water requirement.

On the other hand, buying a large tankless heater for a small to mid-sized home would lead to unnecessary costs.

In case, you’re not well aware of where to start, then all you need to do is to ask a couple of questions to yourself.

The more questions you’ll ask yourself the better clarity you’ll have about what you’re looking for.

For example, how much water will you need during peak demand?

How many fixtures will you need to run simultaneously during peak hours?

There are two things you need to consider before purchasing a tankless water heater, that is, the flow rate, and the temperature rise.

Flow rate can be defined as the water pressure for a fixture or appliance in gallons per minute (GPM).

On the other hand, temperature rise can be defined as the difference between the incoming groundwater and the desired output temperature.

Flow Rate (Gallons Per Minute)

To determine your total hot water needs, all you need to do is to list the total number of appliances or fixtures that you would be used simultaneously during the peak demand.

Once you’re done with jotting down the flow rates of individual fixtures or appliances that you would be using at peak demand.

In the next very step, you need to sum up the individual flow rate to come up with a number that will depict the total flow rate requirement at peak demand.

In case, you’re unaware of the flow rate of a particular fixture then you can revert back to the manufacturer’s manual.

However, I’ve come up with the average GPM usage for common appliances and fixtures assuming that it would be of great help to you.

Fixtures/AppliancesGallon Per Minute (GPM) Range
Bathroom Faucet2.5 GPM
Dishwasher (High-Efficiency/Standard)0.5 – 1.5 GPM
Kitchen Faucet2.5 GPM
Shower2.5 GPM
Toilet2.2 – 3.0 GPM
Washing Machine (High-Efficiency/Standard)1.0 – 2.5 GPM
Tub4.0 GPM

So, after doing a lot of research, we came to the conclusion that if you’re looking for a residential tankless heater with a motive to run a shower, a kitchen sink, and a high-efficiency washing machine simultaneously, then the overall GPM required at peak demand would be 6.

The aforementioned calculation is just for reference purposes, and my suggestion to you would be to calculate the total GPM as per your requirement.

Temperature Rise

Well, the temperature rise is yet another factor that you can’t afford to ignore, right?

It goes without saying that the groundwater temperature varies across the states and the country for sure.

In fact, the groundwater temperature falls in the range of 30 and 80 degrees Fahrenheit.

Many of you might not be aware of the fact that North America is broken into three climatic zones with average groundwater temperatures as follows:

  • Northern Zone: 37 degrees to 51 degrees
  • Central Zone: 52 degrees to 61 degrees
  • Southern Zone: 62 degrees to 77 degrees

If we talk about the typical home water temperature then it ranges from 110 degrees to 120 degrees.

So, to determine the temperature rise, you need to do a simple mathematical calculation, that is, subtract the incoming groundwater temperature from the output hot water temperature.

Should I opt for a Rheem point of use water heater?

First of all, you need to understand the benefits of a point of use water heater, and why and when you should use it.

The point-of-use water heater could be of great help to you in case you want to use it for the farthest faucet, shower, sink, etc that needs an extra boost of hot water.

Let’s understand it with the help of an example.

Suppose you’ve got a hot tub that uses electric heat, a POU heater can be installed in its vicinity.

These POU heaters are installed in the vicinity of a sink or faucet that needs additional hot water.

They can be easily installed in cabinets or other small spaces.

You can also use POU heaters along with the centralized heating system in order to fetch hot water instantly from the farthest shower, faucet, or any other fixture.


Always look for tankless water heaters that come with a warranty.

I highly suggest you should refrain from buying a unit that doesn’t come with a warranty.

However, the good news is, the Rinnai tankless water heater comes with a longer duration of warranty so you can consider buying it.

The longer the warranty duration the better it is.

Anti-Scale Devices

Look for the models that claim to reduce the buildup of material scale at the bottom of the tank.

The side-effect of scaling is that it shortens the life of the heating element.

So, what you can do is, look for the one that comes with a 12-year warranty, and typically includes a longer and thicker element.

Brass vs. Plastic Drain Valves

Always look for brass drain valves as they are more durable than plastic ones.

If you’re not aware of what drain valves are, then let me tell you, they are situated near the base of the water heater for a garden hose that drains the heater.

Digital Displays

Look for a unit that is equipped with a digital display.

The digital display enhances user-friendliness, convenience, usability by helping you to monitor levels and customize operation.

Gas or Electric: Which Rheem Model Should I Buy?

Frankly speaking, both the models are good in their own sense and come with their own sets of pros and cons.

However, today I’ll try to the best of my capabilities to end up the age-old debate on which Rheem model should I opt for.

Trust me, how your Rheem tankless hot water heater is fueled is a critical decision, and needs to be taken only after evaluating the pros and cons of different types of models available on the market.

The reason I’m emphasizing so much on the type of fuel is that it will impact the size and efficiency of your unit.

And, ultimately, it will determine your annual operating expenses for sure, isn’t it?

Moreover, switching fuel sources can bring a dent in your pocket, and the decision becomes too critical especially if you’re building a new home.

So, the most common fuel choices that we’ve for our Rheem tankless heater are electricity, propane, and natural gas.

I always recommend my clients to go for the type of fuel that is not only cheaper but also readily available in your area.

However, if more than one type of fuel is readily available in your area then you should compare the cost of each fuel and the tankless appliance’s efficiency before making the decision.

Well, if you’re buying an energy-certified model, then you might get rebates for installing a tankless water heater.

To know more about it, CLICK HERE.

We’ve discussed several times the upfront cost of different types of tankless models.

In case, you’re not aware, then let me tell you that gas tankless water is more expensive than its electric counterpart.

On top of it, the former needs annual maintenance for proper functioning.

But, at the same time, in spite of being costlier, the gas tankless heaters have an upper edge when it comes to performance, energy savings.

Gas-Fueled Rheem Tankless Water Heaters

Well, the gas-fueled Rheem tankless water heater could be a great choice for you in case, you’re lucky enough to have either propane or natural gas available in your area at an affordable price.

The thing that I really liked about the gas-fueled Rheem tankless water heater models is that they are highly effective, and the credit goes to the quick response time and high heat output.

Nonetheless, there is more to it rather than only the availability of fuel supply at an affordable rate.

Fuel Supply Line

As the name suggests, the fuel supply line is nothing but a system that supplies tankless water heaters with fuel.

So, if you’re planning to buy a high-capacity Rheem gas tankless heater, then you must check that the fuel line can be resized to meet your fuel demands.

The burners used in the gas Rheem tankless require a huge amount of fuel to provide you with instant on-demand hot water.

In fact, the burners on a gas Rheem tankless system can have outputs in the range of 200,000 Btu/h which is much higher than tank-style water heaters (75,000  Btu/h).

I hope to know it is clear to you why resizing your fuel pipeline is important.

In layman’s language, to accommodate a powerful and highly efficient gas Rheem tankless, you must increase the size of your fuel line.


How many of you’re aware of the fact that there are mainly three types of ignition systems installed in Rheem tankless heaters.

Just for your information, take it as a thumb rule, the more complex the ignition system would be, the more expensive your Rheem tankless water heater would be, and vice-versa.

Please allow me to throw light on each one of them.

Standing Pilot Light
  • Pilot light burns constantly
  • The tankless heaters that use this technology are less expensive and have a simpler ignition mechanism
  • On the other hand, the models using Standing pilot light offers less energy-saving and have higher operating costs
Direct Ignition
  • Rheem tankless heaters that are equipped with direct ignition delivers a spark to the burner when water flow is detected
  • Moreover, such units come with improved energy efficiency over standing pilot light systems
  • In most of the cases, an electric hook up would be required. However, I wouldn’t deny the fact that there are some models that are designed to work without an electric hook rather they use batteries instead
Hydro-Power Ignition
  • Water flows into the tankless system and activates a small turbine that ignites the burner
  • No electric connection or batteries is required


Well, venting is definitely one of the primary concerns for gas on-demand units.

The venting requirements for a tank-styled heater are different as compared to their tankless counterparts.

Trust me, venting a tankless unit has more to do with flexibility.

In fact, in the case of a tankless heater, you’ve got the option to run vents through the roof or horizontally through a side wall.

But, at the same time, you also need to understand that more flexibility comes with more complexity if things aren’t done rightly.

Even the materials used for manufacturing venting for tank-style heaters are different from that of tankless counterparts.

In fact, tankless heaters use a better version of materials that are corrosive-resistant and expensive.

Most materials used for manufacturing category III venting in tankless heaters are stainless steel.

There is a need for category III venting in tankless heaters because standard venting materials will quickly break down because the condensation is highly acidic in nature.

At the same time, I would like to bring to your notice that there are two types of tankless heaters that don’t require venting.

Outdoor Gas Tankless Water Heaters: The reason why a gas tankless heater requires venting is to direct the exhaust outside.

So, if you’re planning to install an outside gas tankless heater, then definitely, there isn’t any need for venting.

Condensing Tankless Water Heaters: These type of heaters uses a sophisticated design that doesn’t require venting.

However, they are more expensive than non-condensing tankless water heaters.

Electric Fueled Rheem Tankless Water Heaters

As we’ve discussed earlier also, the electric fueled tankless water heaters are less expensive as compared to gas-fueled tankless heaters.

Since these units don’t need venting so installation doesn’t require a huge investment.

However, the powerful electric Rheem tankless heaters need a huge amount of electricity so you might have to upgrade the household electrical system, and if that is the case, then a huge investment would be involved for sure.

Since electrical tankless heaters have simpler designs and mechanisms so they are easy to troubleshoot, diagnose, and repair.

As a result, they have a higher efficiency rating and need less nominal maintenance.

To sum up, these units have a longer lifespan as compared to gas tankless Rheem heaters.

Let’s have a quick look at some of the points that will help you to understand why the Rheem electric tankless heaters are the preferred choice.

  • Rheem electric tankless heaters are about one-third the size of Rheem gas tankless heaters
  • Moreover, the Rheem electric models are less expensive than the gas tankless units
  • A Rheem gas tankless heater has an energy efficiency of 80-85% which is far less than the 95-98% energy efficiency of an electric Rheem tankless model
  • You might have to upgrade your home electricity supply if the current system isn’t able to meet the power needs of a Rheem electric model
  • Not only is the Rheem electric model inexpensive to install but also easy to install
  • Requires minimal maintenance and has a longer lifespan
  • On top of it, the Rheem electric tankless water heaters are environment friendly

Benefits of a Rheem Tankless Water Heater

Well, let’s have a quick look at the benefits of a Rheem tankless water heater.

Instant Hot Water

Frankly speaking, with the help of a Rheem tankless water heater you can easily turn any water source into hot water on demand.

Unlike tank-styled hot water heaters, here you don’t have any limitation for hot water supply.

If you’ve done a good job with the sizing, then I can assure you, a Rheem tankless hot water heater would suffice your hot water requirements, be it for faucet, shower, washing machine, or dishwasher.

Lower Energy Bills

There isn’t any standby heat loss, and the unit is designed to heat water only when it is required.

As a result, you save a tangible amount on your energy bills.


They are meant to last longer, in fact, the Rheem tankless hot water heaters last almost twice as long as a tank-style unit.

Space Savings

It goes without saying that most of the tank-styled models require a good amount of space, that is, up to 16 square feet of floor space.

On the other hand, most of the Rheem tankless heaters are the size of a suitcase and can be even wall mounted so you can use your valuable floor space for some other purpose.

Clean, Fresh Water

If you’re using a tank-styled water heater, then the probability is very high that over a period of time, rust and scale might build up inside the tank.

On the other hand, in a Rheem tankless water heater, you don’t have to face such a problem because water is only heated when it is required by you.

In simple words, you’ll always get clean and fresh water.

What is a Rheem Tankless Water Heater?

A Rheem tankless or on-demand water heater heats water only when you need it.

The Rheem tankless water heaters are small, compact, and uniquely designed to be installed in tiny spaces such as closets, exterior walls, etc.

You can use the Rheem tankless heaters to heat your entire home or a single point of use such as a shower, faucet, sink, etc.

The Rheem tankless water heaters come in three models, that is, natural gas, propane, and electric tankless.

These Rheem tankless hot water heaters are meant to provide you with an endless source of hot water.

Also, they are meant to save you a good amount of money on energy costs because these models don’t store hot water in a tank so standby heat loss is very minimal.

Of course, the Rheem tankless hot water heaters are meant to last longer, maybe 15 to 20 years in most cases.

In simple words, Rheem tankless hot water heaters are small devices that are used to obtain instant hot water without the need of storing them in a tank.

How Does a Rheem Tankless Water Heater Work?

Frankly speaking, the working style of a Rheem tankless water heater depends upon the type of model you’re using.

For example, a Rheem electric tankless water heater comprises an element that heats the water when it passes through it.

On the other hand, a gas Rheem tankless water heater has an altogether different working mechanism.

So, as soon as you open a faucet, shower, or any other appliance, the Rheem tankless water heater recognizes the need for hot water and starts the heating process.

Moreover, the temperature of the incoming water is used to calculate the amount of heat the burner needs to produce to deliver water at the desired temperature.

As soon as the demand for hot water ceases, the unit shuts down and stops using energy, waiting until more hot water is needed.

But, at the same time, you also need to understand that sizing for the Rinnai tankless unit also plays a significant role when it comes to achieving an optimum result.


So, finally, here I’m with the most awaited section wherein I’ll respond to your queries related to Rheem tankless hot water heater reviews.

Who makes Rheem tankless water heaters?

Well, the brand Rheem is a privately held American manufacturing company that is known to produce high-quality yet affordable residential and commercial water heaters.

The company also produces and sells products under the Ruud brand name.

The Rheem was founded in 1925 by Richard and Donald Rheem and is headquartered in Atlanta, United States.

In case, you want to know more about the Rheem company then click on this link.

How long do Rheem tankless water heaters last?

Rheem is one of the most respected and well-established brands in the tankless water heater category.

The on-demand water heaters manufactured by this brand will last somewhere between 8 to 12 years.

Where are Rheem tankless water heaters made?

Rheem is based in Atlanta, with manufacturing plants in Fort Smith, Montgomery, Ala.; Oxnard, Calif.; and Eagan, Minn.; and a parts distribution center in Randleman, N.C. In 1987, Rheem became a wholly-owned subsidiary of Paloma Industries of Nagoya, Japan, the world’s largest producer of gas appliances.

Can I install a Rheem tankless water heater in the same place where my old water heater was installed?

As long as enough combustion air is provided, Rheem tankless water heaters can be installed in a utility room, garage, basement, or attic, or on an outside wall.

Plus, they can be installed in locations where a storage water heater may not fit.

The Digital Temperature Controller can be mounted in any room.

How much can I expect to save on my monthly bill if I install a tankless water heater?

Well, most of the tankless water heaters that I’ve come across, and as per the various tests conducted across the tankless models, it has been found that Rinnai gas tankless heater costs up to 40% less to operate than an electric Rinnai water heater, and up to 30% less than a natural Rinnai gas water heater.

Where in my home can I install a Rheem tankless water heater?

In simple terms, it depends.

What I mean is, depending upon the Rinnai tankless models, you can decide where you can install it.

For example, RTG-64DV, RTG-84DV, and RTG95DV may be installed in all locations, including bedrooms and bathrooms.

However, the aforementioned models are not designed for use in mobile homes.

On the other hand, RTG-64X, RTG-84X, and RTG-95X are outdoor models and are designed for outdoor installations only.

These outdoor Rinnai tankless models not only saves you space but also the cost of venting.

Does Rheem offer customer service for their tankless water heaters?

Definitely, yes, Rheem offers customer service for their tankless water heaters.

In fact, the customer service is available 7 days a week from 7 am to 7 pm, central time.

What is the Uniform Energy Factor (UEF) for the Rheem Tankless Water Heaters?

The Department of Energy required manufacturers to calculate the UEF based on how efficiently each water heater uses energy in real-world usage scenarios.

The standard was intended to enable homeowners to compare the efficiency of one water heater to another.

UEF replaces the old standard, Energy Factor (EF), which didn’t allow easy comparison.

What does e5 mean on Rheem tankless water heater?

Well, if I’m not wrong then e5 is an error code that depicts an imperfect combustion alarm.

The error code 05 will occur only when there is an issue with combustion.

It could be triggered by a blockage to the vent exhaust or an issue with the air intake.

What is code 11 on a Rheem tankless water heater?

The error code 11 depicts ignition failure.

So, when your Rheem tankless hot water heater displays an error code 11, then it simply means the ignition has failed.

Frankly speaking, there could be numerous reasons behind the occurrence of this error code so my suggestion would be to contact a professional to troubleshoot this problem.

What is code 13 on a Rheem tankless water heater?

An error code 13 will only display on Indoor Rheem tankless systems.

  • Check that the air intake and exhaust venting is correctly installed and in good working order. It’s critical that the exhaust is NOT recirculating into the unit’s fresh air intake.
  • Inspect and remove any blockage from the venting and where the vent terminates outside.
  • Check and verify that the altitude settings reflect your location.
  • Check the Flame Rod FL-24.
  • Check Blower Motor. 

How do you clean a Rheem tankless water heater?

Honestly speaking, flushing a Rheem tankless water heater is very important for its longevity and hassle-free operation.

And, it becomes a really important process that you can’t afford to skip especially if you’re living in an area with hard water conditions.

To be honest, over a period of time, lime and scale build-up inside your Rheem tankless unit will definitely happen, and the best way to get rid of it is by flushing the unit on a regular basis.

Well, if you’ve not used any Rheem tankless hot water heater earlier, then let me tell you, the most critical element for not only Rheem tankless heaters but any tankless heater is a heat exchanger.

A heat exchanger is the portion of the tankless heater where the heat from the burning gas is transferred to the water.

Moreover, if the sediment is obstructing the normal water flow, then the performance of your tankless heater will degrade for sure.

So, are you interested in knowing more about the flushing process?

  • First and foremost, you need to turn off the electrical power, gas supply, and water supply on your Rinnai tankless water heater before you expedite the flushing process
  • Secondly, use two garden hoses and attach them to the drain valves
  • Once done, in the next very step, you need to connect one side of the first garden hose to the cold water supply on your tankless unit, and the other side to the circulating pump
  • Make sure that the pump hose goes into the bucket
  • With the other garden hose connect the hot water valve on the unit and put the other side to the bucket
  • This step is crucial and needs to be carefully executed, all you need to do is to pour approximately five gallons of food-grade white vinegar into the bucket
  • Then, open the drain valve and also switch on the pump and let it run for an hour or so
  • After switching off the circulating pump, drain vinegar from your Rheem tankless hot water heater
  • Open the main water valve and allow cold water to flush the system for at least a couple of minutes if NOT MORE
  • The best thing about most of the Rheem tankless water heaters is that they come with an inlet water filter to protect the system from specks of dirt, remove it, and clean the sediments
  • However, before you expedite the filter cleaning process, don’t forget to turn the main water valve off
  • Put the water filter back, open the water valves and purge the air from the system by opening the hot water tap
  • Check for leaks
  • Turn the gas and electricity on and then run the Rheem hot water heater
  • And, once you’ve expedited the aforementioned steps, your Rheem tankless hot water heater will definitely get new life with improved efficiency and performance along with the elongation of the lifespan of your heat exchanger

Rheem Electric Tankless Water Heater Installation Process

I’m attaching a self-explanatory video for your perusal.

It is highly recommended that you watch the entire video without skipping any portion in order to reap the maximum benefits.

Rheem Tankless Water Heater Troubleshooting

Most of the time, my clients get confused about what to do when the Rheem tankless error code is displayed.

And, if you’re also a first-time Rheem tankless buyer, then the probability is high that you might have faced a similar situation in the past, right?

If you’ve bought a Rheem tankless that comes with remote control, then maybe pushing both up-and-down arrows on the remote will do the trick for you by resetting the error.

Let’s have a quick look at some of the important steps that can help you to get rid of the errors.

  • First and foremost, turn off all hot water faucets
  • If you’re using a remote control, then turn off the water heater by pressing the power on/off button
  • Wait for at least 5 minutes and then press power on/off to turn on the water heater
  • Turn on the hot water faucet and check for an error display
  • Repeat the process if necessary

For more details, you can click this link.

Rheem Tankless Water Heater User Manual

In case, you’re looking for a Rheem tankless water heater user manual, then you can download it HERE.

Wrapping Up the Rheem Tankless Water Heater Review

First and foremost, I would like to thank you for being with us till the end.

Secondly, I would like to bring to your notice that I along with my core team have put loads and loads of effort in coming up with this idiosyncratic superlative comprehensive buying guide on Rheem Tankless Water Heater.

In case, you liked our effort and want to appreciate us then please do share this piece of information with the ones who are in need of it.

After all, sharing is caring, isn’t it?

Trust me, all the Rheem tankless models that made to our list are of high-quality and worth the investment.

Frankly speaking, the term “best” is relative and not absolute so the Rheem tankless unit that might cater to your needs may not be even worth buying for me and vice-versa.

So, my suggestion to all my readers would be to look for the Rheem tankless heater that not only caters to their needs but also falls well within their budget.

Please do let us know in the comment section which is your favorite Rheem Tankless Unit from our list.

And, also let us know if any other Rheem tankless model, you want us to review.

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