Takagi T-H3 Tankless Water Heaters Review

A review of Takagi water heaters, Takagi T-H3, T-H3J, T-H3S, and T-H3M, designed with the tankless and condensing technology for heating water in small and large homes. Check out and compare the advanced features, benefits, differences, main specs, or what you should know to buy the best model.

Designed small but powerful, Takagi T-H3 tankless water heaters (available on amazon.com) are ideal for whole-house water heating, on-demand and in a continuous supply and used in residential and commercial applications. And not only for potable water heating but space heating and recirculation as well (some models).

Takagi T-H3 tankless water heaters: Buying tips

Feature review

Superior efficiency

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

The primary heat exchanger is made of high-quality HRS35 copper alloy that ensures durable and reliable water heating. Such a strong material provides excellent resistance to thermal and mechanical stress that occurs at high temperatures.

An advanced design provides high energy efficiency with an energy factor of over 0.90 that complies with the ultra-low NOx standards, making such a tankless water heater green, environment-friendly and ideal for regions with strict emission laws. Condensing models are the most advanced units on the market, expensive to buy but are saving big on energy.

Advanced electronics

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 in the purchase.

The advanced electronics, diagnostic system, and LCD screen ensure easier troubleshooting than devices without. The controllers utilize functions such as; an info button to display the water flow, inlet and outlet hot water temperature in F and C, status indicator, error display, and push buttons, making it very convenient to use.

Improved safety

Proper combustion is very important because the unit can maximize performance and savings, and users are safe from sooting and carbon monoxide exposure. This is why every model from Takagi has the air-fuel ratio sensor (AFR) to ensure a proper mixture between air and gas.

Internal freeze protection ensures that the device won't get damaged due to freezing weather, so homeowners who live in the north do not have to worry.

The bypass and flow adjustment valve are not present on every heater, but only the best ones, such as the Takagi T-H3 model. The valve helps in providing the optimal water flow control, accuracy, and durability, especially in high demanding applications, such as for commercial usage.

Other common safety features include the hi-limit switch protecting the heater and surrounding from extreme temperatures; overheat cutoff fuse that shuts off the water heater if the heat exchanger is exposed to too much heat; and other sensors and thermistors, including the electric board, which keeps everything running smoothly.

All the condensing models use PVC venting, which provides more flexibility during installation, is cheaper, and deals with ultra-low NOx gas emission, which helps in protecting the environment from pollution.


While most tankless water heaters come with a 12-year warranty, Takagi offers 15 years in a residential application, 5 years in commercial applications, and 5 years on other parts.

Model review

There are several models found in this condensing group: T-H3, T-H3J, T-H3S, and T-H3M series, each designed for different house sizes or a number of applications used.

Takagi T-H3M

Takagi T-H3M-DV, as an indoor and T-H3M-OS as an outdoor model, are the smallest condensing models that come with only 120,000 BTU of gas power, the maximum water flow of 6.6 GPM, and energy efficiency of 0.91, making them ideal for smaller homes and apartments, with the 1.5-2.5 baths. They use the standard 3/4" water connections and ½" for gas.

Indoor models have a temperature controller integrated into the front of the unit, while it is provided with the outdoor model.

The lightweight design of 44 lbs allows easy handling and installation almost anywhere, especially at the point-of-use application.

Takagi T-H3J and T-H3S

Takagi T-H3J-DV and T-H3J-OS are indoor and outdoor models designed to deliver the maximum power of 160,000 BTU, the hot water flow of 6.6 GPM, and an energy factor of 0.95. If you live in a mid-size home with 2.5 to 3.5 showers, this is the right model for you.

Takagi T-H3S-DV and T-H3S-OS are stronger models that use gas burners with higher gas input than the previous model - 180,000 BTU, which allows them to deliver more hot water - 8.0 GPM with the same efficiency. These models are built for larger homes, with up to 4 baths.

These models have the same size of water connections, but the gas connection has to be larger - ¾".

T-H3J and T-H3S series look the same; they are more stylish than the T-H3M series and 20 pounds heavier.

Takagi T-H3

Takagi T-H3-DV and T-H3-OS (available on amazon.com) are the largest and most versatile models from this manufacturer equipped with the strong 199,000 BTU eco-friendly gas burner that can deliver a high 10 GPM water flow with an efficiency of 0.95. The T-H3 series is recommended for larger homes, delivering plenty of hot water to up to 4.5 showers simultaneously and commercial applications such as restaurants, space heating, and recirculation systems. T-H3 is the only model that is NSF Certified Food Equipment approved.

When comparing all the models here, you will see that T-H3 models look the same as T-H3J and T-H3S models, have the same size and weight but are more powerful, have stronger (commercial-grade) elements, and produce more hot water.

What makes T-H3 unique is the ability to use Easy-Link and Multi-Link systems where up to 4 or up to 20 units can be connected and used in high-volume applications.

This makes them suitable for very demanding applications - where the maximum gas input can reach a high 796,000 BTUs.

Hot water temperature is easy to control either by using the built-in temperature controller or a dipswitch, using one of 17 settings to adjust the temperature between 100 F and 160 F, or 9 settings found in other models and set the temperature up to the maximum of 140 F.

All these features and advantages over many brands and other Takagi models make the Takagi T-H3 model a good candidate for purchase.

Feature highlights

  • Heat exchangers are made of commercial-grade HRS35 copper alloy and stainless steel and are built to increase durability and reliability. The manufacturer provides a 15-year warranty in residential applications and 5 years on commercial. A heat exchanger made of the commercial-grade copper alloy - HRS35 is found only on a Takagi H3 model, while other models use the standard copper C1220.
  • Bypass and flow adjustment valves are used for optimal temperature control and precision.
  • The venting is flexible, offering indoor and outdoor installation options. An air supply pipe can be made of ABS, PVC, CPVC, PP, or steel. Direct venting can use a horizontal side or vertical through the roof termination. Also, based on personal preference and installation options, you can choose between the single pipe system with the room air intake and the two-pipe system with the air intake from the outside.
  • A direct vent system requires 3" or 4" PVC venting pipes with a maximum length of 100 ft and with zero clearance to combustibles.
  • Takagi T-H3 models are designed to heat potable water and space heating and use them in recirculation systems.
  • The temperature remote controller is built into every indoor model and provided with outdoor units.
  • Built-in AFR sensor (air-fuel mixture ratio) provides the proper gas combustion, which results in increased efficiency and low emission.
  • An Easy-Link system for connecting up to 4 units on T-H3 models.
  • A Multi-Unit system connects up to 20 units on T-H3 models.
  • Computerized safety.
  • The freeze protection system ensures that water temperatures inside the heat exchanger never fall below a certain value.
  • The hi-limit switch ensures safe temperature levels of hot water.
  • The overheat cutoff fuse protects the unit by shutting it down if the temperature of the heat exchanger increases above the safe level.


Water Flow
(GPM) @ 30 F rise
10 8 6.6 6.6
Energy Factor
0.95 0.95 0.95 0.93
Min. Water Flow
0.4 0.4 0.4 0.4
Temp. settings
100-160 100-140 100-140 100-140
Noise level
55 55 55 55
Max. vent length
100 100 100 100
59 58 58 44

emergency plumber

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