Frequently Asked Questions

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Buyer's Information

Rinnai tankless water heaters are perfectly suited for virtually any commercial application. They are very versatile. Customers of all sizes and configurations in multi-family, hospitality, healthcare, education, food service, retail and much more trust Rinnai to deliver an unlimited, efficient supply of hot water.

The flexibility and capability of our Rinnai tankless rack system (TRS) allows it to replace just about any existing water heating product, from domestic boilers to traditional tank-style water heaters, as long as the necessary gas, venting and installation requirements are present. In fact, our modular design can handle up to 4.9M BTU. Even in cases where the hot water demands are smaller, Rinnai tankless water heaters can provide significantly more energy efficiency and reliability than tank-style water heaters.

The CU199 models are dedicated commercial condensing models.

To learn more click here.

Yes, there are some differences for the CU199 which includes:

Built in cascade controller to link up to 24 units
A Thermal Efficiency rating (96 97% thermal efficiency)
New common venting configurations (room air and sidewall intake with vertical exhaust)
Temperature settings from 98°F to 185°F, right out of the box

Uniform Energy Factor (UEF) calculates a water heater's overall energy efficiency with other heaters with similar hot water output over a 24-hour period. On the contrary, Thermal Efficiency is the amount of energy delivered as heated water compared to the energy consumption of the water heater. The two figures are related but different and the Thermal Efficiency calculation is used specifically for commercial applications.

Yes, the tankless rack system comes standard with the CU199 for most applications, however there are othter options that utilize the Rinnai RU and RUR units if your desire a recirculation pump internal to the tankless unit. These units are configured with Temperature settings from 98°F to 185°F, right out of the box.

The commercial warranty is 8 years on the HEX or 12,000 hours of operation, five (5) years on parts, and one (1) year on labor.

No. The CU199 models are for commercial use only.

No. The CU199 is for commercial use only and is not certified for use in mobile homes.

The Demand Duo® R-Series is a certified single appliance by CSA. The Demand Duo® H-Series is an assembly with multiple and separately certified components- tank, CU199 tankless, controller, and pump are standalone certified components.

The Demand Duo® H-Series model CHS13080H is suitable for residential or light commercial use.

For more information on Rinnai’s robust line of residential products, visit

Yes, you can combine a traditional tank with a tankless water heater. The Demand Duo® is a hybrid solution combining the best features of both the tankless water heater and a storage tank. With the Demand Duo® 2 or 2V you can get up to 398,00 Btu delivering up to 551 gallons in the first hour. Depending upon your specific application you may require more tankless units connecting to a storage tank so we invite you to consult with Rinnai’s Applications Engineering Team at 800-621-9419 or to determine the best solution for your project. We are here to help.

Typically you won’t notice a difference in hot water performance when you have low-flow faucets or showerheads. If you find you’re not getting the hot water you need, start by lowering the temperature setting on your tankless water heater by a couple of degrees. It’s counterintuitive, but it affects the hot/cold mix ratio and will activate the tankless water heater unit for lower-flow fixtures.

Also, remember many single-handle faucets have limit stops that affect the hot/cold mix and may need to be adjusted. If this is the case, it may be helpful to check with the manufacturer of your faucet or consult the faucet manual for details on how to make these adjustments

The Hugo X-1 is a battery backup system — also known as an Uninterrupted Power Supply (UPS) — for tankless water heater products and more. Designed specifically to run your Rinnai tankless unit without power for multiple days, The Hugo X-1 will also keep your computer or cellphone powered until power is restored. The Hugo X-1 is available now for order from your local Rinnai Ace Dealer.

We don’t make an electric model, because there are several potential drawbacks to electric tankless water heater units. First, the power requirements of electric units large enough to provide hot water for a typical household can be prohibitive. For example, a unit that can provide three gallons per minute with an 80° F temperature rise would require about a 150 amp 230 VAC circuit. That’s about eight times the power required for a three-ton central air conditioning system!

Second, the relative operating cost of electric tankless water heaters is much higher than gas water heaters. Based on national averages, electricity costs nearly twice as much per BTU as natural gas. Even with propane, gas tankless water heaters are considerably less expensive to operate than those that run on electricity.

Rinnai Tankless Water Heaters are not UL-rated but they are certified by CSA International to ANSI Z21.10.3 Standard Gas Water Heaters, Volume III, Storage Water Heaters with Input Ratings Above 75,000 Btu/h. However, the following internal electrical components are UL-certified:

Transformer E (UL 1411)
Relay (UL 41515)
Wire & Conduit (UL 1430)

Good news: The short answer is yes. Rinnai tankless water heaters feature freeze protection for outside temperatures as cold as -22° F (-30° C) for indoor models or as cold as -4° F (-20° C) for outdoor models when protected from direct wind exposure and as long as the appliance has both power and gas supply. The pipes feeding the unit must be heat-traced and insulated to provide the necessary freeze protection.

Rinnai strongly recommends the installation of an optional drain-down system on units installed outside in cold climates. Once installed, the system allows water inside the unit to drain out if there’s a power and/or gas outage or a component failure. See the owner’s manual for optional drain-down system piping.

Rinnai tankless gas water heaters need a demand of at least 0.4 to 0.6 gallons per minute of water flow through the hot side to ignite and 0.26 gallons per minute to stay in operation. If the flow rate falls below these levels, the energy-efficient Rinnai unit will turn off because it senses that hot water isn’t needed.

There are several possible solutions to minimum flow rate issues. You can try lowering the temperature on the unit to avoid cutting in too much cold water; cleaning the inlet water filter on the cold water inlet of the unit to remove sediment buildup that can decrease flow; cleaning or removing the aerators from showerheads or fixtures; or replacing low-flow showerheads or fixtures. If you believe that none of these are the issue, contact your original installer or plumber to service the unit.

The estimated life expectancy of a Rinnai tankless hot water heater is twice as long as that of a traditional tank.* Actual performance will vary depending on water quality, usage rates, environmental conditions and regular maintenance. This longevity is one of the factors that makes a Rinnai tankless water heater a money-saving choice over time.

*Based on DOE ENERGY STAR® lifecycle estimates

The life expectancy (or useful lifespan) of a Rinnai tankless water heater is up to 20 years. Actual life is impacted by water quality, usage and proper maintenance. For comparison, a tankless water heater lasts about twice as long as a tank water heater, making them a better value in the long run.

Up to 30 on-demand recirculation accessories are supported per module. There is no limit per the type of accessory as long as the total number of accessories do not exceed 30.

No. Setting up on-demand recirculation does not require the homeowner’s Wi-Fi network.

No settings are affected by a power outage.

Yes, because push buttons and motion sensors are paired to the module. If the module is swapped, the on-demand accessory (push button, motion sensor, etc.) must be factory reset and paired to the new module.


There are two types of periodic maintenance that your service technician should perform to keep your Rinnai tankless water heater in top shape. It’s important to note, the time in between necessary maintenance will depend on the water quality in your home.

1. The in-line screen filter should be checked periodically for debris and cleaned.
2. The unit should be flushed periodically to keep it free of scale and lime, which can shorten the water heater’s lifespan over time. This process should be completed by a professional installer. Please contact an installer near you.

Our How to video just in case you want to do some maintenance on your own.

Read the full article from Fine Home Building - Master in a Minute Video: Tankless Water-Heater Maintenance


What size gas line does a Rinnai Tankless Water Heater require? Rinnai Tankless Water Heaters are designed to provide maximum performance and efficiency using either a 3/4" or 1/2" gas line, as long as sufficient gas flow is available. An undersized gas line can stress a tankless system and possibly reduce its lifespan, all Rinnai tankless water heaters are equipped with technology that safely ceases operation if they detect an inadequate gas flow. This innovative feature safeguards the unit from compromising performance and efficiency.

The tables below list the maximum length for both 1/2" and 3/4" gas lines when paired with Rinnai Tankless Water Heater models. Note: that Table 1 is intended for Natural Gas and Table 2 is intended for Low-Pressure Propane Gas supplies.

Table 1: Intended for Natural Gas
Rinnai Tankless Water Heater Models
Name Plate Ratings (BTU/H)
SCH 40 Metallic Pipe Size (Maximum Equivalent Length)
1/2 Inch
3/4 Inch
V53e 120,000 100' 450'
V65e, V65i 150,000 70' 300'
RUC80i, RU80i 152,000 70' 166'
RL75i, RL75e 180,000 50' 200'
V75i, V75e 180,000 50' 200'
RLX94i 192,000 40' 175'
RUC98i, RU98e 199,000 40' 175'
RL94i, RL94e 199,000 40' 175'
RUCS65i, RUS65e 130,000 100' 350'
RUCS75i, RUS75e 160,000 60' 250'
RU130i, RU130e 130,000 100' 350'
RU160i, RU160e, RUR160i, RUR160e 160,000 60' 250'
RU180i, RU180e 180,000 50' 200'
RU199i, RU199e, RUR199i, RUR199e 199,000 50' 175'
Rating is based on 1 Ci. Ft. Nat’l gas = 1,000 BTU
INTENDED USE: Initial Supply Pressure: 8.0" w.c. or greater; Inlet Pressure: <2 psi; Pressure Drop: 3.0" w.c.; Specific Gravity: 0.60
Source: NFPA 54/ ANSI Z223.1 National Fuel Gas Code

Table 2: Intended for (Low-Pressure) Propane Gas
Rinnai Tankless Water Heater Models
Name Plate Ratings (BTU/H)
SCH 40 Metallic Pipe Size (Maximum Equivalent Length)
1/2 Inch
3/4 Inch
V53e 120,000 50' 300'
V65e, V65i 150,000 30' 175'
RUC80i, RU80i 152,000 30' 175'
RL75i, RL75e 180,000 20' 125'
V75i, V75e 180,000 20' 125'
RLX94i 192,000 20' 100'
RUC98i, RU98e 199,000 20' 80'
RL94i, RL94e 199,000 20' 80'
RUCS65i, RUS65e 130,000 40' 200'
RUCS75i, RUS75e 160,000 30' 150'
RU130i, RU130e 130,000 40' 200'
RU160i, RU160e, RUR160i, RUR160e 160,000 30' 150'
RU180i, RU180e 180,000 20' 125'
RU199i, RU199e, RUR199i, RUR199e 199,000 20' 80'

INTENDED USE: Pipe Sizing Between Single- or Second-Stage
(Low-Pressure) Regulator and Appliance. Initial Pressure: 11.0" w.c; Pressure Drop: 0.5" w.c.; Specific Gravity: 1.50

Source: NFPA 54/ ANSI Z223.1 National Fuel Gas Code

Here are the steps needed to properly size your gas line:
Determine what type of gas is being used
Determine inlet pressure
Determine the allowed pressure drop
Determine what other types of gas appliances are sharing the gas line
Determine the maximum loads expected on the whole system as stated in the National Fuel Gas Code

NOTE: For complete information on gas sizing for Rinnai Tankless Water Heaters, consult the 'Operations and Installation Manual' that comes with your unit. Or, consult a licensed Rinnai installation professional who can help guide you through the process.

Rinnai offers a limited Field Conversion Program. Kits for converting gas tankless water heaters from natural gas to propane or vice versa are available for most models. Please have your installer or service provider call us at 1-800-621-9419 to find out if your model qualifies and to obtain a detailed step-by-step conversion instruction kit.

These kits are available directly from Rinnai. They will be shipped only after the installer or service provider has contacted Rinnai’s technical support services and consulted one of our technical specialists, to ensure the installer or service provider is qualified to perform the conversion. The Field Conversion Program is available for installed units where the gas type availability has changed. For safety, it’s not approved for use in conversion of non-sold inventory or mobile homes.

Rinnai Tankless Water Heaters require 120 volts AC, 60 Hz and less than three amps.

PC Board settings inside the tankless water heater must be configured to enable recirculation. For more information, see section: Step 2: Connect Module to Water Heater and Configure Settings

1. Check out the latest tips and tricks for a successful, stress-free installation
2. Additional wiring can run up to 300 feet (91 m) away from water heater (18-22 gauge wire required).
3. Running cold water through the recirculation line will not force the pump to turn on.
4. The OFF cycles for Circ-Logic are determined by configuration settings of the water heater PC Board. For optimal usage of the on-demand accessories (push button and/or motion sensors), the water heater must be set to Comfort mode. Comfort mode cycles the pump more frequently ensuring the loop temperature remains higher. Power cycling or factory resetting the module will not reset Circ-Logic.
5. For best results and maintaining hot water in the loop, all lines should be insulated.

Learn more about the optimal places to install and mount your control•r™module by watching our video 'control•r™module location and mounting by Rinnai's control•r™ Wi-Fi Module attaches easily to the Rinnai Tankless Water Heater by a two-wire interface and quickly connecting through the local Wi-Fi network. Proper mounting and location of the control•r™module ensures quick set, minimal disruptions and quality connection.

Push Button Installation Tips:
The maximum distance from the module to a push button is up to 250 ft. (76 m).

The push button requires two CR2450 watch batteries (available at most retail stores including Walmart, Home Depot, etc.). Battery life is up to two years.

Once installed find out 'How to pair your Rinnai control•r™ module and unit with push button' by watching our instructional video Wireless push button pairing your Rinnai Tankless Water Heater control•r™module with your installed push button that can be mounted near the point of use, like a kitchen faucet or bathroom sink, and operates the recirculation system.

You have five minutes to complete the pairing process before it times out. If pairing mode times out, press and hold down the Connect button on the module until the LED turns GREEN.

When pairing multiple on-demand accessories, you must enter pairing mode for each accessory. For more information, see section: Step 2: Connect Module to Water Heater and Configure Settings.

Factory Reset Defined: (PURGE Internet Network and Password information) Factory Reset restores the module back to its factory default values. Factory resetting also erases all current settings and wireless network history.

A Factory Reset must be performed when changing wireless networks (you must factory reset first, and then select the new network). A Factory Reset must also be performed when starting over on the pairing process (you must factory reset first, and then start the pairing process).

How To Factory Reset - Press and hold the Connect button (see below) on the module until the LED blinks WHITE, and then release. The module will reboot and the module LED turns solid RED when complete.

Power Cycle Defined: (REBOOT) Power Cycle shuts down power to the module and then restarts power (which is the same function as removing the water heater plug from the power outlet and then plugging it back into the outlet). When trying to connect or disconnect power to the tankless water heater, Rinnai recommends using the water heater power plug instead of using the Reset feature on the module. DO NOT insert a small pin into the Reset opening, it WILL NOT reset your module.

Rinnai Alternative Pairing Tool - This tool is only for pairing a control•r module with your 2.4Ghz wifi network. Please follow the steps exactly as described. This method works with either your personal computer or the web browser on your mobile phone/tablet.

Instructional video for the MC-91-2 Controller provides information on the LED Display, Controllers and Indicators
Some topics include those listed below and more...

Temperature setting under the priority function
Maintenance monitoring mode
Auxiliary functions of the controller such as changing from Fahrenheit to Celsius, control panel locking, etc.

MC195T Controller is used to control recirculation performance with Rinnai Tankless Water Heaters that have recirculation logic.
Note: Optional feature for luxury and some ultra RU series models. However, standard for the RUR Ultra Model series.

Topics Include:

Control panel details
Setting the clock
Adjusting the temperature
Timer overview and adjustment
Override features
Lock features
Silence beep

If your Rinnai Tankless Water Heater has recirculation capability, you can activate recirculation though the use of the control•r™ Module. The module can be wirelessly paired with motion sensors or push buttons. Learn how to set the recirculation parameters to ensure your getting the most from your tankless water heater by watching our video 'Setting Recirculation parameters for your control•r™ Module.'

Thermal Efficiency is the amount of energy delivered as heated water compared to the energy consumption of the water heater.

CU199 models come with an MC-91-2 temperature controller (integrated into indoor models; provided with outdoor models) with temperature ranges from 98°F to 185°F. They do not require the MCC-91 temperature controller.

There are multiple, flexible venting options available with either twin pipe 2" or 3" Schedule 40 PVC/CPVC or 2"x4" 0r 3"x5" Concentric venting. You can also common vent up to 12 units using Rinnai supplied Polypropylene or Schedule 40 PVC/CPVC.

Room air common vent with vertical exhaust Common venting with sidewall intake with vertical exhaust Common venting is ULC S636-approved

Yes, they may be installed together and common vented or tied into a recirculation loop. Both the Demand Duo® H-Series and R-Series have the capability to control building recirculation with the New DuoSmart Digital Controller.


At this time, we don’t recommend this. However, testing is underway for this installation type. Since every commercial job is different, we recommend you contact a Rinnai commercial application engineer to discuss options tailored to your unique situation.

Yes. The CU199 is approved for elevations up to 10,200 feet.

Don’t worry: That “smoke” is likely just water vapor. During cold weather, when the exhaust temperature is much hotter than the outside air, the exhaust fumes condense producing water vapor.

By design, the fan will keep running for a short time after the flow of water stops. This helps ensure constant water temperatures during rapid starting and stopping, as well as exhausting any residual gas flue products from the unit. It will turn off on its own after a few moments.

A Rinnai tankless water heater features built-in freeze protection, so it will remain in operation in temperatures as low as -30℉. In order to use this feature, you must have both power and gas run to the unit. In addition, the pipes into the tankless water heater must be heat traced and insulated to protect them from freezing. A Rinnai-certified contractor or approved plumber will follow installation recommendations so your unit can operate optimally, even in cold weather.

Press and hold the Connect button on the module until the LED blinks WHITE, and then release. This will restore the module back to original factory settings.

Remove the accessory batteries, and then reinsert the batteries while simultaneously pressing down on the accessory Connect button.

Is the push button paired properly? You can check by pressing the push button. Does the LED on the module turn green? If yes, then the push button is paired properly. If no, try re-pairing. See section: Step 2: Connect Module to Water Heater and Configure Settings.

Make sure the water heater dip switches/parameter settings are set to Comfort mode (for steps, see section: Step 2: Connect Module to Water Heater and Configure Settings).

The pump may be in a mandatory dormant (inactive) state due to Circ-Logic (see section: How On-Demand Recirculation Works for more information).

If the module is in pairing mode, the LED on the module is solid green.

Remove the accessory batteries, and then reinsert the batteries while simultaneously pressing down on the accessory Connect button.

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