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Your Guide to Home Heating and Cooling Systems

Last Updated on January 20, 2022

Rinnai RL75iN Tankless Water Heater Review


Sustainable Reliability

We’re continuing our extensive reviews of tankless water heaters, and Rinnai came out on top again for mid-size to large homes. The RL75iN tankless water heater from Japanese manufacturer Rinnai reliably and efficiently provides hot water for up to three showers at one time. If your home needs a constant supply of hot water, or you find yourself running out of hot water at peak times, you will enjoy the benefits of replacing your traditional water heater with this indoor tankless model. It’s smaller than traditional water heaters, and you’ll never run out of hot water. It is also compatible for recirculation to ensure that you always have hot water as soon as you turn on the faucet. If you’re replacing your current tankless water heater, note that the RL75iN provides 7.5 gallons of hot water per minute. If your needs fall at or below this flow rate, you will undoubtedly be pleased with the RL75iN’s performance and user-friendly controls.


Is It Worth Your Money?

The Rinnai RL75iN indoor, natural gas water heater will outperform any traditional (tank) water heater both in hot water delivery and longevity. It constantly heats your water as it passes through the heat exchanger, so as long as you’re not using too many fixtures at one time, you’ll never run out of hot water. You can also expect the unit to last 20 years, whereas a tank water heater will fail after 10-15 years.

You’ll also enjoy being able to install the RL75iN in any room of your house. It takes up a small amount of wall space, has an attractive appearance, and is easily accessible with a temperature control setting of 98-140-degrees Fahrenheit.

You will rarely need to perform any maintenance on this tankless water heater, and the company provides a 12-year warranty on the heat exchanger (5 years on other parts). If you want added convenience, you can add a recirculation pump that keeps hot water pumping and reheating through your pipes at all times.

If you do not need 7.5 gallons per minute, however, you would do well to consider the smaller Rinnai V65iN model, which provides 6.5 gallons of hot water per minute for approximately $500 less than this nearly $1200 model. That being said, if you do need a higher flow rate the RL75iN won’t disappoint you, and with an expected lifespan of 20 years, the convenience is well worth the initial investment.

Detailed Review & Breakdown

The Rinnai RL75iN tankless water heater will benefit nearly every home, but before you buy, here’s what you should know. We’ll detail the features, specifications, ease of use, installation requirements, pros and cons, and the cost of purchasing the RL75iN for your home.




The RL75iN is a natural gas tankless water heater that constantly heats the supply of water as it passes through the unit’s heat exchanger. As the model name implies, you can rely on it to provide up to 7.5 gallons of hot water per minute. That rate of water delivery is adequate to run four fixtures at one time: two showers, a dishwasher, and a laundry machine (or the equivalent thereof).

The Rinnai RL75iN will come at a pre-set temperature control of 120-degrees. You can save on your natural gas bill by lowering the output to 98-degrees, or if you’re running a long plumbing line or need to fill a hot tub, you can raise the temperature up to 140-degrees.

If there is a problem in your water line, the Rinnai RL75iN’s leak detection feature will automatically close the valve to the water supply, helping to prevent further damage and flooding. It also has a built-in thermometer to detect the ambient temperature. If the environment gets too cold, it will activate its anti-frost protection, running at low energy to prevent the water currently in the unit from freezing and bursting the pipe.

Though not included, it is important to note that the RL75iN is compatible for recirculation. With an added recirculation pump, the water heater will continuously reheat the same water flowing through your pipes so that you’ll have hot water the moment you turn on a faucet or open a valve.


  • Weight: 50 pounds
  • Width: 14 inches
  • Height: 23 inches
  • Depth: 9.3 inches
  • Color: Silver
  • Voltage: 120
  • Gas Type: Natural Gas
  • Gas Line Fitting: .5 inches


The RL75iN tankless water heater fits comfortably on your wall and runs easily on the same amount of voltage as a regular light switch or power outlet.

Ease of Use & Reliability

The RL75iN’s user interface is simple to operate, and if there is a problem with the unit, its error indicator lights will help you diagnose and troubleshoot the issue. You can expect this unit to last 20 years or more, and Rinnai covers the heat exchanger with a no-cost warranty for 12 years (5 years for all other parts).

With such easy operation and long life expectancy, the RL75iN is a nearly hassle-free investment for your home.

Because it is so small and taps into your existing plumbing and electrical lines, you can easily install the Rinnai RL75iN tankless water heater in almost any room of your house. Place it in a central location between the bathrooms, kitchen, and laundry room to ensure fast hot water delivery to your showers, appliances, and faucets.

Note that adjusting the temperature control will raise or lower the output of all of your fixtures. You can change the temperature setting as often as you like, but remember to reset it when you’re finished with your Jacuzzi spa time and want to turn on the faucet to do the dishes. 140 will feel pretty hot when you’re not expecting it.


The RL75iN is a high capacity tankless water heater that it is compatible for recirculation. It is competitively priced at less than $1200. You will most likely need additional parts for installation (~$180) or professional installation services (~$1200) to complete the task.

Any Other Criteria?

You will need to install and connect the RL75iN. Doing so will require cutting into your drywall and roof, performing electrical, plumbing, and gas line maintenance, and then finishing the project with flanges and roof sealer, patching and repainting your wall. You can purchase the valve and termination kits to make your job a little easier.

If you’re not comfortable performing the installation yourself, however, you will need to hire a professional. Attempting to install a tankless water heater without the proper tools or training can be dangerous and can cause damage both to your home and the water heater.

Is This The Tankless Water Heater For You?

Heating 7.5 gallons per minute, the Rinnai RL75iN is sufficient for families of 5-6 or those who need a large amount of hot water at peak times. If you have a large home, install the water heater in a central location between bathrooms and the kitchen to minimize wait time for hot water delivery.

Our Winner

The Rinnai RL75iN does jump in price compared to lower capacity models, but that extra gallon of water per minute does make a difference. Five hundred dollars spread out over 20 years is a negligible amount to pay for the convenience of supplying your whole family with hot water.

This model rarely fails or needs maintenance, especially if you soften your water. You can also add a recirculation pump to the system for immediate hot water.

Overall, we’re impressed with the Rinnai RL75iN and would recommend it to any family with the need for an increased hot water supply.

Other Options Worth Looking At:

If you don’t think that you need quite that amount of hot water at any one time, we recommend the smaller Rinnai units, such as the V65iN or the RUC98iN, which will also help you save on your natural gas costs.

If you need more hot water, Rinnai offers hybrid models with up to 40-gallon tanks that continually refill to meet the needs of even the busiest home. They also offer propane counterparts for all of their models if you would rather use a different fuel source.

Read More: Outstanding Rinnai Tankless Water Heater

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