Takagi T-H3, T-H3J and T-H3S Review

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The review will cover three Takagi models; Takagi T-H3, T-H3J and T-H3S, all designed small but powerful enough to provide on demand and continuous supply of hot water in residential and commercial applications. These water heaters are built not only for heating potable water but for space heating and recirculation (some models).

Model review


One of the greatest features found on Takagi water heaters from T-H3 (540 series), T-H3J (240 series) and T-H3S (340 series) series is the condensing technology. Condensing technology utilize not one, but two heat exchangers where the secondary HE is made of the high quality stainless steel to ensure corrosion-free operation in the acidic and low-temperature environment.

Such an advanced design provides the high energy efficiency of over 90% that complies with the ultra-low NOx standards. Condensing models are the most advanced units on the market, expensive but big in energy savings.

Another great benefit is that every indoor tankless water heater from Takagi has a built-in temperature controller while the outdoor units include the wall-mount remote controller and also the advanced electronics for easy troubleshooting. Both controllers utilize the same functions; info button to display the water flow, inlet and outlet hot water temperature in F and C, status indicator, error display and push buttons.

Takagi T-H3J

Takagi T-H3J is tankless and high-efficient water heater that also provides the ultra-low operation for the reduced impact on the environment. These units are available as an indoor and outdoor models. T-H3J-IN is an indoor unit that uses direct vent system to remove the products of combustion out. As an outdoor model, T-H3J-OS does not use the venting system.

Either with or without the remote controller you can use 9 temperature settings for temperature change which goes from 100F to 140F.

T-H3J series can be installed only as a single unit because it does not have an option to use the Easy-Link or Multi-Unit systems.

Takagi T-H3S

Takagi T-H3S series is another group of ultra-low NOx water heaters with the condensing and tankless technology that are available as the indoor T-H3S-IN and outdoor T-H3S-OS models. These include the same features as the above models but have more power and can provide more hot water. The maximum water flow is 8 GPM that makes it ideal for homes with the 2 to 3 showers, while the previous model has the water flow of 6.6 GPM for use in homes with 1 to 2 showers.

Takagi T-H3


Takagi T-H3, with its high 10 GPM water flow, is recommended for homes with the 3-4 showers, commercial applications such as restaurants, also space heating and recirculation systems. When comparing T-H3 with the T-H3J and T-H3J models, the main differences are the higher power and water flow and the ability to use the Easy-Link and Multi-Link systems to connect up to 4 or up to 20 units for even more power and water flow.

The temperature of hot water is easy to control either by using the temperature controller or dipswitch and model T-H3 has more settings (17) where the temperature can be adjusted from 100F to 185F. The energy factor on all three models is the same, 0.95.

All Takagi tankless water heaters from T-H3, T-H3J and T-H3S series incorporate the heat exchanger made of the high quality HRS35 copper alloy that ensures durable and reliable water heating. Such a strong material provides a great resistance to the thermal and mechanical stress that occurs at the high temperatures.

Takagi T-H3 is not only for the residential water heating, but for commercial applications, featuring the bypass and flow adjustment valve for the optimal control and precision in high-volume conditions. T-H3 is the only model that is NSF Certified Food Equipment approved.

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Quick feature review

  • Commercial grade heat exchanger made of HRS35 copper alloy, designed to increase durability and reliability.

  • Bypass and flow adjustment valve for optimal temperature control and precision.
  • Flexible venting with indoor and outdoor installation options. Air supply pipe can be made of ABS, PVC, CPVC, PP or steel. The direct venting can use horizontal side or vertical through the roof termination. Also, based on the personal preference and installation options, you can choose between the single pipe system with the room air intake and two pipe system with the air intake from the outside.

  • Direct vent system requires 3" or 4" PVC venting pipes with the maximum length of 100 ft and with zero clearance to combustibles.

  • Takagi T-H3 models are designed for heating not only potable water but space heating and use in recirculation systems.

  • Temperature remote controller is built-in in every indoor model and provided with every outdoor unit.

  • The built-in AFR sensor (air-fuel mixture ratio) provides the proper gas combustion which results in an increased efficiency and low emission

  • Easy-Link system for connecting up to 4 units on T-H3 models.
  • Multi-unit system connects up to 20 units on T-H3 models.

  • Computerized safety
  • Freeze protection system ensures that water temperatures inside the heat exchanger never falls below certain temperature.

  • Hi-limit switch ensures safe temperature levels of hot water.
  • Overheat cutoff fuse protects the unit by shutting it down if the temperature of heat exchanger increases above the safe level.


Water Flow
(GPM) @ 30 F rise
10.0 6.6 8.0
Energy Factor
0.95 0.95 0.95
Min. Water Flow
0.5 0.5 0.5
Activation rate
0.4 0.4 0.4
Temp. settings
100-185 100-140 100-140
Noise level
55 55 55
Max. vent length
100 100 100
59 58 58


Takagi manufacturer provides a long warranty of 15 years on heat exchanger if used in residential applications, 10 years in commercial, and 5 for other elements.

(Pictures courtesy of Takagi)