Takagi Tankless Water Heaters

Tankless water heaters were once the wave of the future, but now they are gaining in popularity every day as homeowners and business owners alike discover the benefits of instant water heating technology. Takagi is a leader in the industry and is known as one of the best tankless water heaters. PlumbingSupply.com® is your source for Takagi tankless gas water heaters -save on your water heating bills, and save the environment!

ACCESSORIES for Takagi tankless water heaters

VENT PIPE for Takagi tankless water heaters

Stay safe and learn how to turn off your gas in the event of a natural disaster or emergency

Please note: some areas do not allow installation of a few of these water heaters. Read more.

Takagi Tankless Water Heater Information

Comparison Chart

Model Max BTU
Flow Rate
1st Hour
(H x W x D)"
Indoor or Outdoor
140,000 19.500 0.75 - 6.6 180 gal/hr
(77°F rise)
NG: 0.81
LP: 0.81
NG: 81%
LP: 81%
37-1/2 lbs 20.5 x 13.75 x 9.5
Indoor or Outdoor
190,000 19,500 0.50 - 8.0 246 gal/hr
(77°F rise)
NG: 0.82
LP: 0.82
NG: 82%
LP: 82%
48 lbs 20.5 x 13.8 x 9.5
Indoor or Outdoor
199,000 19,500 0.50 - 10.0 252 gal/hr
(77°F rise)
NG: 0.82
LP: 0.82
NG: 82%
LP: 82%
39 lbs 20.5 x 13.8 x 8.5
199,000 11,000 0.50 - 7.0 252 gal/hr
(77°F rise)
NG: 0.827
LP: 0.833
NG: 82.3%
LP: 83.6%
40 lbs 20.5 x 13.8 x 8.5
235,000 25,000 0.75 - 9.6 300 gal/hr
(77°F rise)
NG: 0.81
LP: 0.82
NG: 82.3%
LP: 84.7%
70 lbs 24 x 18 x 9

Flow Rate Guide (Temp Rise vs GPM)

Temperature Rise (F°)
Model 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110
TK-110U Indoor or Outdoor 6.6 6.6 5.7 5.1 4.6 4.2 3.8 3.5 3.3 3.1 2.9 2.7 2.4 2.3 2.2 2.1
TK-310U Indoor or Outdoor 8.0 7.8 6.9 6.2 5.7 5.4 4.8 4.4 4.1 3.9 3.7 3.5 3.3 3.1 3.0 2.8
TK-510U Indoor or Outdoor 9.0 9.0 8.1 7.3 6.7 6.1 5.6 5.6 5.2 4.9 4.6 4.3 4.0 3.7 3.4 3.1
MOBIUS T-K3-PRO 7.0 7.0 6.9 6.2 5.7 5.4 4.8 4.4 4.1 3.9 3.7 3.5 3.3 3.1 3.0 2.8

Quick Installation Check List

Knowing what you need to do when you are deciding whether to buy a tankless water heater or not can help save you money!
Category Sub-Category Description
Electrical Voltage 120 VAC electrical ground all the way back to electrical service panel
Water Pressure A steady 40 - 60 PSI for maximum flow
Quality Hard water must be treated with softener or conditioner
Well Water Water pressure must be checked & mineral contents treated
Pipe Material No galvanized supply water pipe
Valves Pressure relief only, no T&P
Recirculation lines should go through a small electric water heater and not directly back through the Takagi tankless water heater
Gas Gas Type Factory Set For Natural Gas And Includes Liquid Propane Conversion Kit
Pipe Size Minimum 3/4" I. D. (inside diameter)
Pressure (NG) 4.0 - 10.0 WC (water column inches) (7.0 WC ideally)
Pressure (LP) 8.0 - 14.0 WC (water column inches) (10.0 WC ideally)
Air Material Exhaust: 4" stainless steel, cat III
Intake: 3" any material - seal connection
Layout 4" exhaust must be individually run per unit all the way to outside
No common venting
No increase or decrease in diameter
Venting Length 25 - 60ft depending on unit - Deduct 5ft for each elbow used in the venting
Condensation Must have condensation drain when linier run exceeds more than 5ft to protect heat exchanger
Air Supply
Air supply from outside: 1sq. Inch / 15,000 BTU
Air supply from inside: 1sq. Inch / 1,000 BTU

How Takagi Tankless Water Heaters Work

Picture of how a Takagi tankless heater's works internally

Takagi Tankless Water Heater Single Unit Recirculation Example

How to plumb a recirculation system with a tankless water heater

Takagi Tankless Water Heater Multi Unit Recirculation Example

How to plumb a recirculation system when you have multiple Takagi tankless water heaters linked together in a series

Frequently Asked Questions

Q. "What type of vent do these tankless water heaters require?"
A. These tankless water heaters require Category III stainless steel vent only.

Q. "I've heard that some Takagi tankless water heaters cannot be installed in a few areas. Is that true?"
A. Yes, there are some counties that do not allow for the installation of a few Takagi tankless water heaters. For this reason, the person purchasing one of the following models is responsible for checking with their local code authorities prior to ordering: T-M32-NG, T-D2-IN-NG, T-D2-OS-NG, T-K4-IN-NG, T-K4-OS-NG, T-KJr-IN-NG, T-KJr-OS-NG. Here's a list (not complete) of some California counties that do not allow these water heaters to be installed: Sacramento, Yolo, Sonoma, San Joaquin, Napa, Marin, Solano, Contra Costa, San Francisco, San Mateo, Alameda, and Santa Clara. Again, this list is not complete, so it's up to the purchaser to check with local code authorities prior to ordering.

All Takagi Tankless Water Heaters must be installed by a licensed professional.

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