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Rinnai RL75iN Gas Tankless Water Heater Review

Rinnai RL75iN

Our Rating
Rinnai RL75iN review
  • Energy Efficient
  • Superb Flow Rate
  • Easy controls
  • Durable & Eco Friendly
  • 5 years warranty on all its parts

10 main Features of The RL75iN

1) Dimension and Design

This model weighs 50 pounds, its voltage is 120 volts, its dimensions are 14 x 9.3 x 23”, and it comes in silver color.

Most people may worry about the look of how their water heaters, so rather hide them in the attic or the garage.

You really don’t have to worry about this, as Rinnai has a really modern design that suits your taste.

Thanks to its relatively small dimensions, you can accommodate it almost wherever you want, as long as you have a way to set up the venting system there.

2) Warranty

It comes with a 1-year labor warranty for all residential installations, a 5-year warranty on all its parts, and a 12-year written guarantee for the heat exchanger.

When compared to other similar products, this offer is really amazing.

We checked with people who have been using it for a while, and it seems that there are no design flaws or long-term problems with this water heater.

3) Compatibility

The RL75iN tankless gas water heater is ideal for homes that have 2 to 3 bathrooms, and it will definitely have a positive effect on your energy bill.

What is even better, according to the manufacturer, is the fact this water heater can also be used commercially, you just need to purchase the commercial controller separately.

4) Efficiency

rinnai gas tankless water heater reviews

A very important point to check when buying a water heater is thermal efficiency, which is at whopping 82% in this case.

Another thing you might want to know about is overall efficiency. This Rinnai model takes the cake there. 

It will reliably deliver an almost instant and never-ending amount of hot water.

A very important point to check when buying a water heater is thermal efficiency, which is at whopping 82% in this case.

Another thing you might want to know about is overall efficiency. This Rinnai model takes the cake there. 

It will reliably deliver an almost instant and never-ending amount of hot water.

At the end of each month, you will notice that you got up to 40% energy savings when compared to your previous water heater.

Depending on the use, it requires 10,300 to 180,000 BTU’s per hour. A tank style gas water heater will need a gas supply of about 40,000 BTU’s per hour, but, unlike this tankless model, they will be spending gas all day long.

This Rinnai model will only spend natural gas while the water is running.

5) Water Flow Rate

This model delivers up to 7.5 gallons of hot water per minute. The water is at an accurate and consistent temperature.

You can run hot water on two or three different places in your home at once, without a hitch.

So, two showers and a sink are no problem for Rinnai RL75iN. The response isn’t instant – you don’t get hot water the moment you open the valve, but you’ll get the desired temperature within 30 seconds or less.

Basically, you’ll just wait for the existing water from the pipes to leave, and that’s it.

6) Safety

One of the reasons we can honestly recommend this model is the smart safety system it comes with. Thanks to this system your water heater will be sound for years.

If your water composition needs more frequent descaling, or if you don’t follow the cleaning schedule, this unit has scale detection system.

This system will prevent any damage to the unit due to those two reasons by simply automatically shutting it off.

Other than that, this water heater also has built-in leak detection. If Rinnai somehow springs a leak, it will detect it and shut itself off.

This way to prevent water damage, and we honestly like that they thought even of the worst case scenarios.

7) Controls

We love the controls Rinnai offers. Some water heaters nowadays are almost annoyingly high-tech, to the point where you need a manual whenever you want to increase the water temperature.

We like that Rinnai decided to go with a simple, yet modern control panel.

It comes with a MC-91-1US digital controller. Its display is unobtrusive, and it lets you set up everything you need. 

You can adjust the temperature (98-140 degrees for residential use, and 98-160 degrees for commercial use) and use a temperature lock that will prevent accidental temperature limit and settings changes.

Another thing this display will be great for – if a problem exists, the unit will identify it and put a notification with the error code on the display.

Other Types of Applications:-

  • For more info on radiant floor heating, check out this article.
  • Looking for an under sink heater instead? Click here.

8) Venting

For this model, you need a Rinnai venting kit, and it comes with the heater itself. It uses outside air for combustion.

This makes it even more safe to use, and suitable for installation in bedrooms and bathrooms where B-vent heaters simply can’t be installed.

Of course, there are some limits as to where and how you can terminate the vent, but the user’s manual is more than clear on that.

Check out our reviews if you are looking for an electric tankless water heater instead.

9) Durable and Eco-friendly

Rinnai has thought about being green as well. These water heaters operate with a reduced amount of water and energy consumption, CO2 and NOx emissions.

Plus, as their expected lifespan is about 20 years, they reduce the amount of waste in the landfills.

10) Maintenance

This high-tech water heater will save you a lot of cash, but you need to do regular maintenance. If you don’t it might break down, and cost you a lot.

Regular maintenance for this Rinnai model means flushing the system at least once per year. That way you take care of the calcium deposits that inevitably form inside.

If you don’t do this, the energy efficiency of this product will be significantly reduced, you’ll get water temperature that varies, and, you might even end up with a plugged heat exchanger.

The Pros and Cons


  • Excellent price to value ratio, the perfect mid-range water heater
  • .82 energy factor
  • You can easily have three things running at the same time, and experience no shortage of hot water


  • Packaging can be improved

Why Buy Tankless?

You already know all about standard, classic water heaters, about how they work and how much energy they waste. That is why tankless models have become very popular lately.

Their compact design and amazing energy efficiency are the main reason more and more people decide to take them. They heat water only when it’s needed, so there’s no unnecessary heating to keep the water in the tank warm. 

Another great thing – the length of your shower is not limited by the size of the tank. Read our article on our best gas tankless water heater for other brands other than Rinnai. 

Final Verdict

Rinnai RL75iN Gas Tankless Water Heater

Our Rating

Most reviews on the Rinnai RL75iN are outstanding and for a good reason. Its capacity, energy efficiency, and additional features make it one of the very best on the market. The only flaw here is that the packaging during arrival can be improved.

If you’re looking for something that is eco-friendly and will serve you well for years to come, this model is definitely something you should consider. We rate this model 4.8 out of 5 stars from us.

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    Verner Ellen

    Hi, my name is Verner Ellen. I am a homebody whose interest is in getting the best home tools and equipments to help with the the everyday house chores. I also love fitness, cooking and grilling. Maintaining a clean and comfortable home is my lifelong passion.