Takagi TKJr Water Heater Review

Takagi TKJr tankless water heater is the smallest gas model for water heating from Takagi manufacturer, and is mainly designed for light residential applications. This article reviews its top features and specification.

takagi tkjr tankless gas water heater

Takagi TKJr as the smallest unit from Takagi, is only 20 inches tall, and is a good substitution for 40-gallon tank-type water heater, making it ideal for small homes, apartments, condos or offices, for both residential water heating and radiant heating applications. Another advantage is its affordable price.

Features and Specs

Power and efficiency

Takagi TKJr tankless water heater, with its 140,000 Btu/hr provides enough heating power for homes with up to two bathrooms. TKJr models that are operating on natural gas have the smaller energy efficiency (81%) than the propane gas models (83%). Due to its high energy factor Takagi Jr liquid propane model qualifies as an Energy Star unit.

On TKJr models that are using natural gas, heating power can be reduced to 19,500 and 17,500 Btu/hr for the propane gas units, all thanks to its design, which allows modulation on the gas valve.

Flow rate

If you live in the area with the ground water temperature of close to 60 F, TKJr model can provide 3.8 gpm with the 60 F temperature rise. Maximum flow through the TKJr water heater and its heat exchanger is 5.8 gpm. Takagi TKJr model doesn't provide an option to increase the hot water production by using the Easy-Link system for multiple configurations, such as the advanced models.

Temperature control

Recommended temperature of hot water is 120 F and Takagi Jr is built to provide four preset temperatures; from 113 to 183 F, but if you want to have better control and more accurate temperature of hot water, then you should buy a TK-RE20 temperature controller.

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Takagi TKJr model is power vented, but you can also convert the unit to work as the direct vent with a sealed combustion, for the installation in the confined space, by using the optional TV09 conversion kit. Also, depends on the installation viability and your preference, you can mount the Takagi TKJr indoor or outdoor (outdoor kit is needed).

Takagi TKJr uses 4" category III stainless steel vent to extract the products of combustion, and it can be installed vertical or horizontal. If used as direct vent option, 3" air intake pipe diameter is recommended, made of PVC, ABS, galvanized steel and has to be sealed airtight. TKJr model is equipped with the combustible air sensor designed to shut off the heater if there is not enough air flow for the combustion.


All gas and water connections are designed as 3/4" NPT, minimum water flow to trigger the burner is 0.75 gpm.

Advanced features

Other important features are the electronic ignition with the flame sensor, self diagnostic system for troubleshooting and safety, and the computer that monitors water temperature, water flow rate and gas flow to ensure that you are getting the right amount of hot water at the desired temperature.

Safety features

To protect the heating system and its users, Takagi TKJr water heater is equipped with several safety features including:

  • Built in freeze protection that contains several ceramic heaters built into the unit.

  • Manual reset Hi-limit switch that is set at 194 F.

  • Inlet and outlet thermistors to monitor the incoming and outgoing water temperature.

  • Overheat cutoff fuse to protect the heat exchanger from the excessive heat.

  • Flame sensor to verify the ignition and that flames are extinguished when the unit is OFF.

  • Air/Fuel ratio rod.

  • Flue back-draft pressure switch.

  • GFI power supply connection.

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(Photo credit Takagi)