Takagi T-D2 Tankless Water Heaters

An overview of the indoor and outdoor Takagi T-D2 and T-D2U tankless water heaters designed for homes with two to four bathrooms and light-duty commercial applications, so as the recirculation applications. Check out the features that make T-D2/U models versatile and green.

Model review

Takagi T-D2 tankless water heaterTakagi T-D2

Takagi T-D2 models are coming from the non-condensing group of tankless water heaters where the energy factor, for both natural gas and propane models, is 0.82, which is the same as other tankless units from this group.

Takagi T-D2 heaters are designed as conventional on-demand models, while the T-D2U models as ultra-low NOx - recommended for the areas with the strict gas emission law.

These tankless models can work as a single unit providing the maximum water flow of 10 GPM, which is enough hot water for two to four showers. When using the Easy-Link system, up to 4 units can be manifold into one system generating the maximum flow of 40 GPM - great for high demanding applications.

Ultra-low NOx or T-D2U models can utilize the multi-controller to connect up to 20 units and generate up to 200 GPM of hot water, making the units ideal for larger homes, restaurants, schools, and beauty salons. T-D2 models are NSF approved so can be used in the commercial food industry.



Takagi T-D2-IN-N models are built as indoor units that can use either 3” or 4” vents with the maximum lengths of 50 feet and can be converted to direct vent models with the correct conversion kit. There are also Takagi T-D2-OS-N models that do not utilize any venting due to the outdoor installation.

Note: As the above models are natural gas models, and if you would like to buy a Takagi propane water heater, replace an N with the P at the end of the model number, so Takagi T-D2-IN-N, as a natural gas model, becomes Takagi T-D2-ON-P or a propane model.

Built tough

Takagi T-D2/U are built tough, especially the heat exchanger that is commercial grade and has a thicker wall than other standard types and is made of hardened copper to sustain higher stress and provide longer life.


Takagi T-D2/U is not made for heating potable water only. Due to its capability to provide very high water flow and power makes them suitable for use in space heating and recirculation systems. The pump control port allows efficient operation of the circulation pumps.


Takagi T-D2/U is an advanced type of tankless water heater equipped with remote control, which is the standard feature on many Takagi models. When using the remote control, you can set the temperature on the unit in a range from 99 F to 185 F with the 19 setting options, while with the dipswitch setup, you have fewer options.


  • High-quality, commercial-grade heat exchanger, made of HRS35 copper alloy.
  • Bypass and flow adjustment valve for optimal control and precision.
  • Variety of installation options: indoor as a direct vent and ventless outdoor.
  • Modulating gas burner.
  • It can be used for heavy residential usage of hot water such as space heating and recirculation systems.
  • A temperature remote controller is included.
  • The AFR sensor (air-fuel mixture ratio) for proper gas combustion, increased efficiency, and low emission.
  • Easy-Link system for connecting up to 4 units.
  • Multi-unit system on T-D2U models, up to 20 units.
  • Other safety features include the overheat cutoff fuse, hi-limit switch exhaust, water temperature safety control, and freeze protection system. The safety features are computer monitored and controlled.


T-D2-IN T-D2-OS T-D2/U
Water flow
(GPM) @ 30 F rise
10 10 10 10
Energy factor
0.82 0.82 0.82 0.82
Min. water flow
0.4 0.4 0.4 0.4
Temp. settings
100-176 100-176 100-160 100-160
Noise level
55 55 54 58
Max. vent length
50 N/A 50 N/A
39 39 39 39


Takagi T-D2/U comes with a long warranty; 15 years on heat exchanger if used in residential applications or 10 years in commercial, and 5 for other parts.

If looking to buy a non-condensing Takagi water heater, a model T-D2 is the way to go; while it has many similar features as other, two are making them stand out: an option to connect up to 4 units into one system and therefore increase the water capacity, and commercial grade copper heat exchanger, providing more strength to the most abused element.

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