Rinnai RL75 Tankless Water Heater Review and Buying Tips

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Rinnai RL75 indoor and outdoor water heaters review. Top features and benefits of the Energy Star qualified Rinnai tankless water heaters RL75i and RL75e.

Rinnai RL75 tankless water heaters belong to the "Luxury" series, a series that is built for providing hot water for the medium and large size homes. RL75 models are high-efficient and Energy Star approved (EF, energy factor is 0.82), which makes them eligible for government tax breaks and other utility rebates.


Rinnai RL75 models

rinnai rl75i

Rinnai RL75i is an indoor tankless water heater that is designed to use both natural and propane gas with the concentric vent-type system; one pipe is for getting the fresh air from the outside while other is for the exhaust.

Designed as the direct-vent tankless water heater, it can expel the products of combustion horizontally through the single wall and vertically with the roof penetration. It can even be installed in any room.

Rinnai RL75e is for the outdoor installations only, usually installed in a recessed enclosure, and it does not utilize any vent pipes.

rinnai rl75e


RL75 series as said before consists of two models; RL75i and RL75e, both with the same power of 180,000 BTU and hot water delivery of 7.5 GPM. These two features are what make models RL75i and RL75e recommended for homes with the 2-3 bathrooms.

Commercial grade components

Thanks to its commercial-grade components, Rinnai RL75 heaters can be used in both residential and commercial applications, utilizing both LP and natural gas. One of the most important elements in tankless water heaters is the heat exchanger and Rinnai designs one which has the great thermal transfer while it is exposed to the minimal thermal stress.


As other models from Rinnai, the minimum water flow needed to activate RL75 unit is low 0.4 GPM, which makes it great in situations where the low flow is needed, such as shaving or hand/face washing and for low-flow fixtures.

On the other side, 7.5 gallons is the maximum capacity, but EZConnect system allows two identical models to be connected into one system and provide even more hot water, for the tub, spa or larger home. For larger applications, there is an option to connect up to 25 tankless units by using the multi-unit control system.

Small size

Rinnai water heaters RL75, with its attractive design, fits everywhere, inside or outside. No worries if it is installed inside as it features the sealed-combustion system with a zero clearance. The small size of 14x22.9x9.6 inches allows Rinnai tankless water heaters flexible, wall-mounted installation and valuable space-saving.

Safety elements

  • Flame rod for the flame failure

  • Combustion fan rpm check

  • Boiling protection

  • Glass fuse for over current

  • Thermal fuse

  • Automatic frost protection

  • Remaining flame - OHS

  • Factory equipped with the condensate trap and drain line


  • 12-year limited warranty on heat exchanger and 5 years on other parts

  • The MC-91-1US controller is supplied with the water heater - part of the front panel

  • Meets California and Texas NOx emission requirements

  • Direct electronic ignition

  • Maximum working temperature is 140 F, minimum is 98 F

  • Gas and water fitting size is 3/4"

  • Water pressure range is from 20-150 PSI

  • Isolation and pressure relief valves are included

  • Certified for mobile and manufactured home installations

  • Dimensions: 9.6 x 14 x 22.9"

  • Weight: 50 pounds

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Pictures - courtesy of Rinnai WH company

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