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Rinnai RUC98iN Ultra Series Natural Gas Tankless Water Heater review

Rinnai RUC98iN Ultra Series Natural Gas Tankless Water Heater

If you are interested in buying the best tankless water heater for your home, then the Rinnai RUC98iN Ultra Series is for you. It is very compact in size and has no control knobs. It uses few touch response buttons which can be monitored through the digital display.

The product comes with an energy factor of 0.96 and a BTU of 199,000. It is designed to work perfectly with both concentric and PVC venting options. This product has the highest flow rate in the market, which is approximately 9.8 gallons per minute. It can be used in both commercial and residential apartments. Interestingly, it can power several bathrooms at a time without having a temperature drop.

Key features

The high water flow rate

This product has the highest water flow rate in the market. It has a BTU rating of 199,000 and can produce 9.8 gallons of water per minute. It is designed to serve several faucets simultaneously. Large family households and hotels will find it more useful.

PVC and concentric venting

This double venting feature is rarely seen in other tankless water heaters. You can assemble it very easily because of its variety in the venting option. Rinnai allows you to install it yourself but you must do it properly to maintain its warranty. Also, the two venting options eliminate the need for an adaptor.

Very low nox emission

The advanced design in its venting system allows it to function in a noiseless mode. This model operates very silently when compared to other ones in its category. You can install it anywhere without having to worry about the disturbing sounds.

Energy efficient

With an energy factor of 0.98, it is the most energy efficient tankless water heaters in the market. Another important reason for its efficiency is its sole dependence on natural gas. There is the likelihood that you may experience a little more gas consumption at the beginning, but this will reduce with time. In addition to this, the unit is very cost effective because it has a higher heating capacity when compared to electric water heaters.


The heat exchanger has a warranty of 12 years and 5 years for the parts in residential applications while for commercial applications, the heat exchanger has a 5-year warranty.


  • It comes with two venting options
  • Has a compact and space saving design
  • Digital display with control buttons
  • Temperature button lock to ward off unauthorized users
  • Can supply hot water to multiple faucets without an interruption of the water flow.
  • Has a very high flow rate
  • Certified by energy star
  • Operates quietly


  • The product is highly sensitive and must be handled with care.
  • It is very expensive
  • Can only be repaired by a Rinnai certified agent
  • It is very difficult to install
  • There is the tendency for one to experience a dip in its water pressure

Frequently Asked Questions

Does the product come with isolation and pressure relief valves?

Yes. They come hidden in the box, care must be taken that you don’t throw them away.

Is there a need for an expansion tank for this product?

On isolating the hot side with a check valve for recirculation; you require an expansion tank.

What is the difference between the ruc98i and the ruc98in?

The standard model number is the RUC98i while the RUC98in is an indication of the type of its source of energy which in this case is the natural gas.

Does it come with a flush kit?

No, it does not.

Can PVC be used for the vent exhaust, can these go horizontal through a sidewall, and can the length of this be approximately 20ft?

For PVC, it is, Yes. An upward slope of 5% will be required for a horizontal through the sidewall. The length should be about 10ft.

Does this come with the condensation trap kit? If not, does it need the condensation kit?

No, It doesn’t. However, I will recommend that you check with your local plumbing codes to verify the need for you to plumb it into the sewer line.


This product is the best when it comes to the unlimited supply of hot water, energy saving, water wastage, and environmental impact. The unit is designed to work perfectly in both concentric and PVC vents. However, installation of the unit is expensive in addition to its high price. The good thing is that the warranty is not voided if you install it yourself.

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