Takagi T-H3 Tankless Water Heaters Review and Buying Tips

Takagi T-H3 series of tankless water heaters are built as the condensing models that utilize both natural and propane gas for potable water and space heating. The T-H3 series is known for the high-efficient water heating and ultra-low NOx emission, utilizing quality elements and advanced features and providing long-lasting and convenient operation.

With the energy factors ranging from 0.93 to 0.95, all the units are Energy Star compliant, resulting in decent energy savings and higher than the non-condensing or conventional tank-type models.

Condensing technology uses the secondary heat exchanger (HE), which takes advantage of the high temperature of the exhaust gases to increase the incoming water temperature, boosting the efficiency and decreasing the exhaust temperature. Such technology lowers the installation and maintenance costs as the system uses corrosion-resistant stainless steel and copper alloy HE and inexpensive PVC venting.

The T-H3 series offers excellent benefits; an endless delivery of hot water in steady water flow and a water flow rate of a maximum of 10 gallons per minute, which is sufficient for large homes of up to 5 baths.


T-H3 models review

Takagi T-H3 tankless water heaterTakagi T-H3

All TH-3 models are built as the indoor direct vent (DV) and outdoor models (OS). Both groups are made small, compact, and lightweight, great for the wall mount, and resulting in more floor space than the conventional tank-type units.

Takagi T-H3

Takagi T-H3-DV and T-H3-OS water heaters are the most advanced and strongest models in this group. They come with a the maximum power of 199,000 BTU and water flow of 10 gals/min.

This makes them great for use in large homes with up to 4-5 showers – even homes with heavy usage and small commercial applications.

Equipped with the bypass and flow adjustment valve, these units can deal with the high demanding applications providing ideal control and precision.

The Easy-Link and Multi-Link system allows combining 4 or up to 20 units into the system to meet high-demanding applications easily.

The built-in temperature controller found on indoor models and the wall-mounted remote controllers allows users to set the temperature range from 100 F to 160 F in 13 settings, which is more than found in other models from this group.

Takagi T-H3J

Takagi T-H3J comes with the power of 160,000 BTU and a water flow of 6.6 gals/min, making it great for use in homes with 1-2 showers.

Takagi T-H3S

Takagi T-H3S comes with the power of 180,000 BTU and a water flow of 8 gals/min, making it great for use in homes with 2-3 showers.

All the Takagi models from above are equipped with the quality elements such as the sturdy primary heat exchanger, made of commercial-grade copper alloy HRS35, so they can sustain higher thermal and mechanical stress, which is more than those found in exchangers used on most tankless water heaters.

The secondary heat exchanger is made of 316L stainless steel and is found on all models, including the T-H3M.

Takagi T-H3M

Takagi T-H3M is the smallest unit in this group – it comes with a power of a maximum of 120,000 BTU and a water flow of 6.6 gals/min, making it great for smaller homes and apartments with 1-2 showers. The energy factor is also lower, 0.93 vs. 0.95 for the rest of the models.

Common features

All indoor models are direct vents and must be vented outside, and due to its excellent design, 3" or 4" vents can be used, with the horizontal or vertical termination and lengths up to 100 feet.

For venting, the appropriate materials are PVC, CPVC, ABS, and stainless steel, sizes of 3" and 4" and the maximum length of 100 feet. The outdoor models OS are ventless.

At the front of the indoor models, the temperature controller is built-in, while the outdoor comes with the wall-mount remote controller.

These are used to monitor and control hot water temperature, get the info about operating status and the parameters, and utilize advanced diagnostics for easy troubleshooting.

NoteProfessional installation and repair are recommended. Find local plumbers and get FREE Quotes!

Safety features

As with other advanced Takagi water heaters, the T-H3 series also offers an excellent level of safety such as the:

  • AFR sensor - monitors and maintains the ideal air/fuel ratio for superb performance, high-efficiency operation, and less pollution.
  • Internal freeze protection prevents the unit from freeze damage.
  • The hi-limit switch shuts down the water heater if the internal temperature increases above the safe levels.
  • Overheat Cutoff Fuse protects the heat exchanger from overheating.
  • Surge protection.
  • Exhaust and water temperature sensors.


Models/Specs Takagi T-H3M Takagi T-H3J Takagi T-H3S Takagi T-H3
Power (BTU) 15,000-120,000 15,000-160,000 15,000-180,000 15,000-199,000
Water flow (GPM) 0.4-6.6 0.4-6.6 0.4-8.0 0.4-10
max # of baths 2-3 2-3 3-4 4+
Water/gas connections (inch) 3/4 and 1/2 3/4 3/4 3/4
Temperature (F) 100-140 100-140 100-140 100-140 (160)
Energy factor 0.91 0.95 0.95 0.95
Warranty 15 15 15 15


As it can be seen from the above review, Takagi T-H3-DV and T-H3-OS tankless water heaters are the most advanced and powerful models that provide the highest hot water flow rate, primarily when used with the Easy-Link or Multi-Link systems.

The great thing about every model from this group are the superior efficiency of up to 0.95 and ultra-low NOx emission, allowing users to use less energy, save more money, and lower pollution.

Great versatility includes potable water heating, radiant floor heating, recirculation, direct and indirect heating, and venting through the roof and sidewall using different materials and long vents.


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