Maximum Flow Rate in Gallons Per Minute at 105°F Output temp
Incoming Water Temp:	Flow Rate (GPM)
40°F	2.0 GPM
45°F	2.2 GPM
50°F	2.4 GPM
55°F	2.6 GPM
60°F	2.9 GPM
65°F	3.3 GPM
70°F	3.7 GPM
75°F	4.4 GPM

The Stiebel Eltron Tempra 20 Plus, with a maximum power output of 19.2 KW, is designed for whole house applications in regions where the incoming water temperature is above 60F, and is therefore suitable as a whole house water heater in the southern U.S. and in some warmer northern climates. It is also a popular choice for summer use vacation properties in northern climates where the electrical service does not permit the installation of a larger model. It is also frequently used as a point-of-use heater where more demanding flow rates are required.

Like all Tempra Plus Series tankless water heaters, the Tempra 20 Plus features true microprocessor-controlled temperature regulation as well as a convenient digital temperature display and dial selector which allows you to set the desired output water temperature at any level between 68 and 140F (20 and 60C). It is one of the only tankless water heaters on the market that features a true thermostatic temperature control and full power-modulation based on both the incoming water temperature and the water flow rate. The Tempra 20 Plus will automatically adjust its power output to accommodate changes in the incoming water temperature and flow rate so it can precisely maintain the desired output temperature.

The Tempra 20 Plus also features Stiebel Eltron's exclusive dynamic Advanced Flow Control technology. This technology automatically adjusts the flow of water when the unit's sensors detect that the flow demand is exceeding the heater's capacity. This feature is particularly useful in cold climates and other applications where the electrical service size does not permit the installation of a larger model and it may be desirable to handle occasional high flow demands. It is also desirable where high output temperatures are required for temperature critical applications (commercial dishwashers, etc.) and where flow rates are not always predictable.

Simply stated, the Stiebel Eltron Tempra Plus Series electric tankless water heaters feature the most precise temperature control of any tankless water heater on the market today!

• Digital Display
• Flow Control Technology
• 19.2 kW's of Power
• Thermostatically Controlled
• Requires 125 Amp Service

Stiebel Eltron Tempra 20 Plus Specifications

Thermostatically Controlled?	Yes, digital temperature control and full power modulation based on flow rate and incoming water temperature.
Advanced Flow Control Technology?	Yes, dynamic flow control technology automatically adjusts the flow of water when the unit's sensors detect that the flow demand is exceeding the heater's capacity. This feature is exclusive to Stiebel Eltron Tempra Plus Series tankless water heaters!
Preset Temperature Memory Buttons:	Yes
Flow Rate Monitor:	Yes
Energy Monitor Showing Cost Savings:	Yes
Hinged Case:	Yes
Power (KW):	19.2 KW @ 240v / 14.4 KW @ 208v
Voltage:	208 - 240 volts / single phase / 50 - 60 Hz
Max. Amps:	80 AMPS @ 240v / 70 AMPS @ 208v
Breakers Required:*	2 x 40 AMP (240 volt, double pole breakers)
Wiring:*	Minimum 2 x #8 AWG Copper
Dimensions:	16.6 x 14.5 x 4.6" (42 x 36.8 x 11.7 cm)
Weight:	15.4 lbs (7.3 KG)
Pipe Fittings:	3/4" NPT
Energy Efficiency:	99%+
Activation Flow Rate:	0.50 GPM / 1.9 LPM
Max. Water Pressure:	150 psi (tested to 300 psi)
Max. Output Temperature:	140F (60C)
Max. Input Temperature:	131F (55C)
Warranty:	7 years against leakage / 3 years against defects in workmanship & materials
Safety:	ETL Listed (US & Canada) - meets all applicable standards, including ANSI/UL 499 (USA) and CSA-E335-1/3E-94 (Canada)
Protection:	microprocessor-based thermostatic temperature control (flow rate and temperature modulating) with thermal hi-limit cut-out switch monitoring each heating module
GTIN:	0094922100658

* Breaker size and wire gauge must meet all applicable local, state, provincial, and national electrical codes for your area - these are only guidelines that will apply to most installations. Some codes require use of electrical sub-panel for installation, especially when heater is not mounted within line-of-sight of the main electrical panel. Wiring should be sized to maintain a voltage drop of less than 3% under load. Please consult your electrician for more details.

How it works

The Stiebel Eltron electric tankless water heater is a marvel of technology and engineering - overflowing with technology, yet packaged in an intelligent, simple design. It heats water entirely on demand, only when it is needed.

When a hot water faucet is turned on and the water begins to flow, a sophisticated flow sensor detects that hot water is being demanded and turns the water heater on. Instantaneously, a series of sensors gather information about the flow rate of the water and the incoming water temperature. This information is sent to a microprocessor which calculates the amount of power needed to heat the water to the temperature set point. The water flows through the internal heating modules and exits the unit at the desired temperature. The start-up process takes a couple of seconds. A convenient thermostatic control on the front of the unit allows the homeowner to select an output temperature between 86 and 140F (30 to 60C) [Note: some models are designed for maximum output of 125F (52C)].

The sensors continue to monitor the water flow rate and incoming water temperature as long as the water is running. They constantly send data to the microprocessor so power to the heating elements can be modulated in accordance with changes in incoming flow rate and temperature. If, for instance, the flow rate increases because a second demand for hot water in the home is initiated, the unit will increase its power output to maintain a consistent and precise output temperature.

The tankless water heater will remain on until the hot water faucet is closed. As soon as the flow sensor detects that water has stopped flowing, the power to the unit is completely turned off.

All Stiebel Eltron Tankless Water Heater Tempra and Tempra Plus Series water heaters are manufactured in Germany in one of the world's only ISO-9001 certified tankless water heater manufacturing plants by a company that has been around since 1924!

Please see the internal views of the Stiebel Eltron Tankless Water Heaters below for more details. All of the models utilize the same parts and technology, but have varying sizes and numbers of heating modules.

	Electronic Control Module Sophisticated microprocessor-controlled electronics adjust the power output of the heating modules based on flow rate and incoming water temperature to precisely regulate the output water temp.
	Heating Module The muscle of the system! A series of very high output heating modules (up to 3, depending on model) are used to heat the water as it passes through the heating chambers of the water heater. Each heating module features multiple heating elements. The heating chambers are manufactured with copper - no cheap plastics here!
	Flow Sensor A sophisticated flow rate sensor delivers important data to the microprocessor on a continuous basis - this data is used by the microprocessor to calculate the power level of the heating modules that is necessary to heat the water to the set temperature.
	Safety Thermal cut-off Safety first! Each heating chamber is protected by thermal limit switch, a back-up safety feature that will automatically turn off the heating module if a potentially unsafe output water temperature is reached. This reduces the risk of scalding injuries for children and the elderly, and protects the unit from damage if the microprocessor-based thermostatic control fails.
	Temperture Selector Set it and forget it - use the simple dial control to raise or lower the temperature setting. Tempra Plus series are equipped with a digital temperature setting display. The temperature can be set at any level from 86F (30C) & 140F (60C) [up to 125F or 52C on Tempra 12, 15, and 20] (Not pictured).
	Temperature Sensors Working in conjunction with the flow sensor, a series of temperature sensors deliver important data to the microprocessor on a continuous basis so that the unit can acurately maintain the set output water temperature.
	Wiring Block Convenient terminal blocks are provided to ensure a quick, simple, and safe installation. Installation by a licensed electrician is highly recommended.
	Flow Control Exclusive to Tempra Plus models, the dynamic Advanced Flow Control system will adjust the flow rate of the water if the microprocessor detects that the flow rate exceeds the capacity of the system. The result is the most precise temperature control of any tankless water heater on the market today! Ideal for applications where simultaneous hot water applications occassionally exceed normal model flow rate capacities.
	Sturdy Hinged Steel Case All Stiebel Eltron Tempra and Tempra Plus Series water heaters are housed in a sturdy steel case with built-in wall mounting brackets. Many competitors use flimsy light-gauge aluminum cases or even plastics. Tempra Plus and Tempra Trend models feature a convenient hinged case for easy access.
	Inlet Water Filter The inlet water pipe includes a small screen filter that ensures that no debris is able to enter the system. This filter can be periodically cleaned for optimal flow performance.

Stiebel Eltron Tempra 20 Plus - 239221 Reviews

Great Product
I use these tankless water heaters to replace old or failing water heaters in my apartments. I have ordered 7 so far (installed 5) and everyone loves them, especially me as it cuts down on my maintenance. E-tankless has been great to work with as well. - Eugene P.

Waters Hot and Lots of It
I turn on the water and I get hot water. There's little else to say. Completely satisfied! - Richard L

Magic!
Works great and will even fill my bathtub. My house is 1620 SQFT and I live in Waskom, TX 75692. I have my temperature setting @ 111F. - Josh

Tankless Water Heater
Product works great. - Phil

Very Pleased!
WE are most pleased with our purchase, having been an upgrade from an old 50 gallon tank water heater. We've had readily available limitless hot water since we installed the Tempra 20 Plus system one week ago. - Kyle L

Great product and price.
Received this quickly and had it installed and wired by the electrician. Four weeks later the plumber showed up and it works perfectly. Great having unlimited hot water when needed but no wasted power when it's not in use. - Bill Murchie

SE Tempra 20 Plus
My unit is still performing well as expected five months after installation. Cannot give a fifth star until after ten years, the lifespan of a well-maintained tank type heater. - S. Martin, Florida

---

Other Tempra Plus Series Reviews

Love it.
Great improvement over a hot water heater. Nice to have all the hot water I want and save on bills. More space in garage. - Linda

Excellent unit working with Solar Thermal Hot Water
Purchase and installed my unit in April 2015; wanted to wait a full year before making a review. In a small utility/laundry room I replaced my 40gal electric hot water storage tank with a 60gal storage tank for storing solar thermally heated water. I did not have room for 2 tanks so I decided to go tank less water heating. I reviewed options when professional advise given to me was to go natural gas, but decided after careful study to go with the Tempra 29 PLUS. The savings I am making by preheating my domestic water with Solar Thermal collector panels is showing up as 8kwH/day and the Tempra 29PLUS kicks in when there has been no sun for several days. I have the Tempra set high at 128 and my my solar thermal storage tank set at max temp of 175degF; there are no issues with water at 175degC passing through Tempra...it just does not power on. When there is no sun for several days the Tempra can handle both showers in the home being used at the same time with no issues, and my hydro bill does not kick upwards. A little more expensive to install than a condensing natural gas tankless, but if you have space challenges and cannot get flues out through a wall then this E-tankless is a great way to go, especially with Solar Thermal Hot water preheating. - David F

2 Years Running Strong at the Farm
Don't hesitate to consider going tankless or if your wondering if gas is cheaper etc. I purchased this unit 2 years ago for my farm a to replace a 26 year old water tank. The price per month for electricity is lower and the water hot water is clean because it doesn't sit in the water tank! I installed this with 2 double pole 60 amp breakers and 6/2 wire.. Simple. - Anonymous

SO much better
Purchased this unit to replace another tankless water heater and the Tempra 24 Plus is SO much better. Installation was easy and the flow control on this unit makes all the difference. You can't go wrong with this unit as we have had great success for the 1.5 years we have been using it. - David

Very reliable performance
We installed our Tempra 29 Plus in 2010 and the unit has worked flawlessly since we've owned it. The odd time, we'll adjust the temperature up or down a few degrees, but it has been hanging on the storage room wall untouched for the most part. The heating is very even in the shower and for washing dishes. No temperature fluctuations at all. Other than some fixtures that are a long way away from the heater, the water is heated and arrives as the faucets very quickly. For dishwasher loads (and if there's a hot load of laundry) we always run the closest sink until we get hot water and then turn on the wash cycle. In terms of operating costs, the household hydro bill is slightly higher, but very reasonable. Our gas bill has probably decreased more than enough to offset the increase in hydro. This unit has been very efficient for our family and still operates as well now as it did the day we put it into use. Would definitely recommend this efficient heater to other people here in B.C. or other parts of the country. - Josh

Excellent Water Heater
Excellent water heater. The plumber said it was easy to install. Super tech support, documentation was first rate. But the most important there is plenty of hot water, and no huge tank in the garage any longer. - Pedro

It works as advertised. We are very pleased. - Tom M.

Replacing 10 year old tankless
Saved us money the first month with more efficient operation than our old tankless unit, newer tech very happy with this - B Bailey

Tankless electric water heater.
Works as expected. - Andrew

Great Product - Could be better though
I am very happy with our conversion to tankless. This product is outstanding; well-built and works as advertised. However, I wish the flow detection switch was either more sensitive, or user adjustable. As is, you have to turn the hot water on to a pretty high rate of flow for the heater to kick on. This is fine for most uses, but for things like shaving, where I would normally turn the water on at a slow rate, the flow is not detected by the heater. I turn the water up to solve this, but can't help thinking about the amount of water that is being wasted. One of the reasons I converted is wasted energy on a tank, and now it seems the waste was just shifted to water use. - Ken S

Exceeded my expectations
I installed the water heater in February in Saint Paul, MN. My water temperature coming from the street is probably in the forties Fahrenheit. It is cold enough to make your hands numb. I was a little worried that it wouldn't have enough capacity for my family of 6 with 4 bathrooms. It is working just fine. After some experimenting, we ended up setting the temperature at 115. We can easily take 2 showers at the same time. If the washer and dishwasher are going at the same time, the 3rd floor shower will decrease flow to a trickle without changing temperature. I am very happy so far. I installed it myself. I have a 200 amp service so I had room for the necessary 3 separate 30 amp 220 volt circuits. Some electrical items in the house will exhibit a little fluctuation when the heater kicks in, although it is pretty subtle. Hopefully it continues this performance over the long haul. If it lasts 15 years with this performance, I will be very happy. - John S

Tankless hotwater heater
Outstanding and allows us to use two or more hot water outlets at the same time. Two showers and a dishwasher all at the same time and everyone gets hot water - Ed G

Does what it was intended
Provides unlimited hot water for the house. It runs both showers for 30 plus min with no problem. - Jason H

Fantastic!
The heater is extremely easy to install. It is is even easier to operate. It worked perfectly the moment it was commissioned and performs the same on every use. The water is hot more quickly and it is great to have an endless supply of hot water. E-Tankless was a great resource, responsive, and shipped the heater quickly. They are a fantastic company with great quality products and service. - David Tishim

Fantastic
Love it - Ron T

Performance
We have had our tankless heater for over 6 weeks and it has not failed to produce all the hot water (128 degrees). Several showers at once and a washing machine. Very impressed. Have noticed a slight increase in electric bill but, it's worth it to not have to worry about running out of water! - J. Norton

- Rusty W.

Love my new water heater, light years ahead of my old Sets system. User instructions could be a bit better as could install instructions. Should mention a flushing system should be installed at the same time to get rid of calcium.. - G. Martin

So Far so good
Im in CA and I replaced it in the summer, so far it was easy to install, and easy to work with, I will know if it is the perfect unit when winter comes and the inbound water is colder but so far so good. - Burke Race

overall
So far it is excellent - Oscar Henry

Stiebel Eltron Tempra 24 PLUS Tankless Water Heater
I am very pleased with the performance of my Stiebel Eltron Tempra 24 Plus Tankless Water Heater. It works well is efficient and the staff at E-Tankless were helpful and knowledgeable. I am super happy with my purchase and company service. - Debbie Walsh

Perfect so far
I purchased a Tempra Plus water heater and had it installed by Professional plumber/electrician and it works perfect so far. - Mircea Micula

The Tempra 29 Plus is Fantastic!
After our third water tank flooding the playroom, we knew it was time to do something else. We are so pleased with our decision to go to an electric tankless water heater and definitely with Stiebel Eltron. We chose the refurbished to save a few bucks and has worked out fine. Had they not told me, I would have not known. I did a lot of research and decided it was not worth the cost and relocation to gas. So glad! I was worried about the size since we could not go up to the 36 Plus. No fears. We are never without hot water! The unit is very efficient and cheaper to run than the tank model. Highly recommended! And a special shout out to E-Tankless...I called a few times and they were MOST helpful and informative! - Kathy H.

Excellent!
This thing is amazing! We live in Indiana and it works perfectly. We set the water temperature to 125 and the water was MUCH hotter than our Tank-water heater could ever do, so we moved the temp down to 115 on the dial which literally takes seconds. Non-stop hot water. I have been recommending this to everyone! Takes up almost NO space. You need TWO 6/2 cables and TWO 50 AMP double-pole circuit breakers for the full 100 AMPs of power it may potentially pull, but we have never gotten anywhere close to that. We have saved 10% on our first energy bill. The system literally pays for itself. Spend the money, get the system. Its worth it. I would recommend that you have a water softener if you are getting this water heater. But according to the website, it is not needed. The only difficulty in installation would be that most homes do not have two double-pole 50 amp circuit breakers. These are by no means difficult to install but you should either ask an electrician friend for help, or google it. Works exactly like advertised. We got the Tempera 24 Plus. - Dane

Excellent heater
Bought a Recon Tempra 36 plus Instant Hot water heater for the brewery. Works very well, puts out 140 deg water at 3.0 gal/min. The plus model automatically adjusts the flow to maintain the 140 deg temp. Will allow me to mash direct into the kettle with the water filtered before going thru the heater. Would highly recommend this heater to anyone looking for a whole house instant heater. You just have to make sure you have the AMP capacity to supply the 36 KW heaters. - Dakota Brewery LLC

Etankless
Love it. Very good quality - A Creation By Mario

Second one.
Everything was find, this is our second one. We have that on a process. Your service was excellent, Thanks again - Eric L

Excellent product and service
This is a wonderful product, engineered to German precision specifications. I highly recommend it, and the price was better than anything I could find anywhere else. The service I received was superb and I could not recommend this company any more strongly. Highly professional, courteous, friendly, and full of relevant information. I was impressed from the beginning of the transaction to the very end. I wouldn’t hesitate to make a purchase. Great service and products. - Daniel

Quality Service
The unit is performing wonderfully—but just as important was the expert advice and support that I received from Grant Robertson at E-Tankless - Janice B

Tankless
super easy to install once the electrician finished wiring, the water is hot and for our small home with 2 adults, we have never ran out of hot water. The company was super helpful and the shipping was fast. - Ron

A Really GREAT Product!
I had 3 or 4 other tankless water heaters before I got my first Stiebel Eltron Tempra. All of them failed after a very short while. Then I got my first Stiebel! This thing was amazing! It worked like a charm ... every time for months. I had to send it back for repairs because I didn't realize how hard my water really was (it clogged) and got another Tempra 15 to use while the first one was refurbished. I LOVE the digital temp. control. I just set the temp. at ideal for my shower and never turn the cold water on. One hint: every few months I circulate food grade vitamin C thru the water heater for about an hour using an aquarium pump. That keeps it from getting clogged with minerals and you don't have to use caustic chemicals. This is my third Stiebel Eltron Tempra Plus (the other 2 were lost in a house fire) and I couldn't recommend it more highly. - David C.

Great tankless water heater
Excellent product and excellent support team, thank you! - Gary R Lamarand

I screwed up, they helped
This is a hard review for me to do, as I screwed up. I had two 30 amp breakers and they had the only good looking tankless for a 2 x 30 amp. I ordered it, that was fine, I got the unit and it was in great shape. The install was very easy. My problem was that my 30 amp breaker was only one wire (per breaker) not two as need for the unit too work. Yes, this was in the product literature. So, I screwed up I did not have the right wiring for the unit to work properly. I was able to return the unit. The return went smoothly and well. So if I have any needs for a tankless hot water heater in the future with proper electrical lines I will not hesitate to order from them again. - Mike Berman

Tankless water heater
Best service I've ever had Working great and we love it - Carol Bunyard

excellent water heater
This water heater is extremely good quality and pumps out tremendously HOT water-actually too hot, I had to turn it down so as not to burn us!! - Marshall Swanberg

Tankless Water Heater
We like the water heater. We noticed that sometimes when running hot water at faucit slowly the water heater appears not to detect the flow so it cold water is delivered at the faucit. Otherwise, the product is great - Roger Buchholtz

Satisfied
This is very useful for customers with kitchen that does not have access to gas water heater-which entails coring a hole on the roof of the building. With this, you just install and enjoy. - Seema

Water heater
I have not installed the unit yet, but the service I received in ordering was excellent! She answered my questions and made the process easy. Thank you! - Erin

Stiebel Eltron Tempra 24 Plus Tankless Water Heater
I have not yet hooked up this water heater but I bought it because I own 2 others, same brand different generation. And they both work great, I have nothing but great things to say about them. I expect the same from this one! Thanks for a great product. - Esther Vinzant

Definitely should get if you have a large family
I bought my first Stiebel Eltron Tempra 36 Plus 14 years ago. it was the first generation. I am in the throws of full house renovations and so I bought the new 3rd generation. In 14 years, never once have I had to service the unit. Reliable 100% of the time. We are a family of 8, and the shower is used multiple times a day, every day and our washing machine operates 365/yr. Add to that a dishwasher, and other daily water uses that demand hot water. This is definitely an excellent investment, just by never having to worry about running out of hot water. Add to that, it takes virtually no space, compared to the gas heating/water tank system that was here when we bought the house. The only issue...and it's not a biggie, is that it does require a lot of amps to install, 3 x 60 amps. That said, I upgraded my electric panel to accommodate the new unit along with the other upgrades I did in my renos, however, it was not really an issue for the previous 14 years with my 1st gen unit. This unit pays for itself in the first year (and its really not expensive to start). If you have a large family and need a lot of reliable hot water, and not wanting to worry about showers going cold after 15 minutes of use and waiting an hour for the traditional method of your water tank to fill up for the next shower....then by all means, do yourself a favour and buy a unit. - Jack Daniels

A Homemaker’s Dream! (Big Family)
We are a family of 7 and this has been a game changer for us. There are several improvements I’ve noticed since switching from a traditional hot water tank to this system- 1) it’s foot print is dramatically smaller. In fact, it’s not much of an actual foot print at all since it hangs up on the wall out of the way. 2) I hand wash all of our dishes (3 meals a day as I stay home with our kids) so we have an industrial kitchen sink. Before we got this water heater, I used to have to use one tank of water to fill the sink and then wait a bit to come back and finish washing/rinsing. Not anymore! Now I can do a sink FULL of dishes in one shebang. 3) Before, I could either start a load of clothes OR wash dishes… this is no longer a problem either! I can do both at the same time now! With so many kids (5), anything that makes my life easier (more productive, more simple, etc.) is a big win in my book! And this system is a BIG WIN in my book!!! I’ve already recommended it to several other big families we attend church with and really anyone else that comes over to see the progress we’ve made on our new laundry room (where it’s located in our home). I love it!!! In terms of installation, my husband did it himself. He works construction but plumbing is not his forte but it was simple enough for him to install. But a simple service call with a plumber would suffice, for sure. Ordering, shopping, customer service, etc. with this company have all been wonderful too. Everything has just been great! - Love it!

Tempura 36 Plus
This is the second house that I have built using Stiebel Eltron Tempra 36 Plus tankless on demand water heater. It is an excellent product that is both extremely efficient and has no green house emissions. - Pat

WORTH EVERY PENNY. Great product!
Easy to install, looks good and hot water within 10 seconds. This is a very good & efficient on demand hot water heater. It was a bit pricey but worth every penny! - Michael

Tankless Water Heater
Excellent product, first month i saved about 30 dollars on the power bill. Very easy to install and the water is just as hot as a hot water tank. I would recommend this product, very good investment. - Desmond Chaulk

Wheew
Works fine and we are pleased with the results. - Robert Littlefield

-

Exceptional Water
Carbon filter, water softener and tankless water heater. All operational and working fantastic. The cleanest, softest and continuous hot water I have ever experienced. It all fits in where my old rusty water tank was located. - Mark

Great product.
Direct replacement for my 3 40amp setup. It's performance far exceed that of our previous unit with constant temperature and no variations. Handling whole house with no problem. - James Lansbery

So far, so good
I bought this specific product because it used the maximum voltage available considering my residence's electrical setup (briefed by my electrician here). Water gets sufficiently hot for all purposes, but the heater cannot supply adequately more than one outlet at a time, for the water flow gets too low. I haven't yet used it in wintertime and look forward to seeing if it will be able to heat up the icy cold water. But so far, product is as advertised and satisfactory. - Daniel Bertrand

Stiebel Eltron Tempra 24 Plus Electric Tankless Water Heater
Looks really good. Well packaged and with good instructions. I'm still working on the installation. Have a lot of other things to do before install and start up. Will update this once it's running. - John C L

Stiebel Eltron Tempra 20 Plus - 239221 Customer Questions & Answers

Question:	Can the unit be mounted outside of home?
Answer(s):	None of the Stiebel Eltron Tempra series tankless water heaters are weatherproof so they can't be mounted outside the home without a weatherproof enclosure. They also need to be kept above freezing to prevent damage to the heater. By E-Tankless on Feb 27, 2024

Do You Have Hard Water?

If your water hardness trends above 7 grains per gallon (GPG) or 120 mg/l (ppm), you should consider hard water treatment prior to your tankless water heater. If your hardness exceeds 12 GPG or 200 mg/l (ppm), hard water treatment is strongly recommended.

Hard water treatment helps maintain performance and efficiency, ensures optimal water flow and pressure, and protects your heater from pre-mature failure due to mineral build-up inside the heating module and other components.