Takagi T-H2 Review

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Takagi T-H2 and T-H2S are the most efficient tankless water heaters from this manufacturer. What makes these units special and how it can improve you water heating... read further.

Takagi condensing technology

T-H2 and T-H2S water heaters are designed with the advanced condensing and tankless technology that heat water not only on demand and continuously, but with less than 10% energy loss. 

Takagi added a secondary heat exchanger made of a durable stainless steel to capture the heat from the flue, therefore, increasing the thermal efficiency of the unit.

Since more energy is used for water heating and less greenhouse gases are emitted outside, T-H2 and T-H2S water heaters, both indoor and outdoor models are considered green, whose energy efficiency exceeds 90%. They are also known as condensing water heaters.

Takagi T-H2 Features


Takagi H2Takagi T-H2 was designed to heat water in residential and commercial applications and provide maximum of 9.0 gallons per minute, which can be achieved mainly in warmer areas where the temperature of the ground water is higher. 

With this flow rate, T-H2 can easily provide enough hot water for up to three fixtures. The water heater will provide a flow rate of 4.6 GPM in the areas where the input is 40 F or less, making it ideal for homes with up to two bathrooms.

For homes with the higher hot water demand, Easy-Link is the solution, as it allows linking of up to 4 units into one system. As 4 units are manifold together into the system and with the full automatic modulation the system will operate between 13,000 and 796,000 Btu/h.


Takagi T-H2 tankless water heaters can be installed outside or inside, based on your preference and installation viability. The outdoor model T-H2-OS is usually installed in the recessed box and does not require any venting (power vent is built-in), while the indoor model T-H2-DV is direct vent model with the sealed combustion, that uses a PVC pipe.


Model T-H2, as other tankless water heaters, uses the modulating gas valve to provide hot water with less fluctuation and more accurately, and it ranges from 13,000 to the maximum 199,000 Btu/h.

Temperature control

The temperature is factory set on 120 F and by using the temperature controller TM-RE30 the temperature of hot water can be changed from 100 F to 185 F.

If the remote control is not installed, the temperature can be changed on the computer board and seen on LED and through the small window on the front cover of the water heater.


Takagi T-H2 water heaters are self-diagnostic, which helps in troubleshooting. If there is a problem with the unit an error code (i.e. 111) will appear on the remote control or LED display.

Takagi T-H2S

Model T-H2S can work either as the outdoor T-H2S-OS or indoor unit T-H2S-DV in residential applications. The T-H2S will provide a maximum of 8.0 GPM in colder areas or 4.1 GPM for 40 F rise, which still has enough flow to supply up to three applications at the same time. When compare to a previous model, T-H2S models come with less power, which is approximately 180,000 Btu when on the maximum, while the minimum power is the same, 13,000 Btu.

Due to their condensing technology and high efficient operation where the Energy Factor, EF is 0.91, all models from T-H2 and T-H2S series are Energy Star compliant and therefore, eligible for government tax breaks and other rebates.

Safety features

  • Built-in freeze protection system.

  • Manual reset hi-limit switch. Pressure relief valve not included.

  • Flame sensor.

  • Overheat cutoff fuse.

  • Air fuel ratio (AFR) sensor.


As seen from the above, Takagi T-H2 series are condensing water heaters that utilize the power from the flue gases for higher efficiency. The top features are: an endless hot water supply to up to three bathrooms, on demand use, compact and space-saving design, Easy-Link system for more hot water, computerized diagnostics and adjusting and Energy Star compliance.

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Pictures are courtesy of Takagi WH company