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 the potable water and space heating. 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, but bigger than the non-condensing or conventional tank-type models.

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

The T-H3 series offers great benefits; an endless delivery of hot water in steady water flow and water flow rate of maximum 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 the models are built as the indoor direct vent (DV) and outdoor models, (OS), both groups built small, compact and lightweight, great for the wall mount, and resulting in more floor space available for other use – when compared to 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; these come with the maximum power of 199,000 BTU and water flow of 10 gal/min.

This is what 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 are capable of dealing with the high demanding applications providing an ideal control and precision.

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

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

Takagi T-H3J

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

Takagi T-H3S

T-H3S comes with the power of 180,000 BTU and water flow of 8 gal/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 the commercial-grade copper alloy HRS35, which makes it sustain more thermal and mechanical stress than those exchangers used on most tankless water heaters. The secondary heat exchanger is made of the 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 the power of maximum 120,000 BTU and water flow of 6.6 gal/min, making it great for use in 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 the indoor models are direct vent 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 the temperature of hot water, get the info about operating status and the parameters, and also to utilize advanced diagnostics for easy troubleshooting.

Safety features

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

  • AFR sensor - monitors and maintains the ideal air/fuel ratio, for the superb performance, high-efficiency operation and less pollution.
  • Internal freeze protection prevents the unit from the 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 the 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 is the superior efficiency of a maximum of 0.95 and ultra-low NOx emission.

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


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