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TK-4-IN Takagi Tankless Indoor Water Heater (Natural Gas)
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T-K4-IN-NG has been discontinued
Discontinued April 6, 2019
This product was discontinued by the manufacturer.
MANUALS (4)
This item replaces: T-K3-NG
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Direct Replacement:
Series 200 Ultra Low-NOx Non-Condensing Indoor Tankless Water Heater (8 GPM, NG/LP)
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Product Highlights
–
Natural Gas
8 MAX GPM
Indoor Only
99°F - 167°F
20.3"
8-1/2", 9-1/2" Depth
Description
–
The Takagi brand has been discontinued by the manufacturer as of December 31, 2025. Suggested replacement units will be available on our website and replacement parts will continue to be available as supplies last. If you'd like any further assistance, please contact our customer service team.
Think Green, Save Green. Rebate and incentive programs provide cash-back to consumers for the purchase of appliances that meet certain energy efficiency standards. Most states are offering rebates in the $50 to $250 range. You can search for rebates in your area from here.
Note: Isolation valves are not included but are recommended for installation.
TK-REO2 Remote Control is included: TK-REO2 Remote Control
Released in 2010, the T-K4 improves upon many of the features from the T-K3. The T-K4 is one of Takagi's smaller tankless water heaters. At 13.8 inches wide and weighing only 38 pounds, its ultra-compact design allows it to be mounted on a wall.
Takagi's newest tankless water heater also features an energy factor of 0.82, so it is extremely efficient and environmentally friendly. Since tankless water heaters only burn gas when hot water is needed, installing this unit can help homeowners save up to 45% on their monthly gas bills.
Specifications:
- Capacity: 2 to 3 Bathrooms
- Flow Rate: Maximum 8.0 GPM
- Gas Inputs: 11,000 to 190,000 BTU per hour
- Energy Factor Rating: 0.82
- Inlet Gas Pressure: Min: 5.0" W.C. / Max 10.5" W.C.
- Dimensions: 20.3" H x 13.8" W x 8.5" D
- Direct Vent Capability
- Electric Ignition
Specs
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| Application: | 2-3 Showers |
|---|---|
| Product Type: | Tankless Heater |
| Installation Type: | Indoor Only |
| Fuel Type: | Natural Gas |
| Height: | 20.3" |
| Energy Factor: | 0.82 |
| Width: | 13.8" |
| Vent Size: | 4" |
| Depth (Inches): | 8-1/2" 9-1/2" |
| Max Flow (GPM): | 8 |
| Inlet Gas Pressure: | 5.0-10.5"W.C. |
| Voltage: | 120v |
| Manifold Pressure: | 2.0-2.5"W.C. |
| Gas Input: | 11000-190000 BTU/h |
| Energy Star Rated: | No |
| Water Connection: | 3/4" |
| Venting Requirement: | Category III Stainless Steel |
| Gas Connection: | 3/4" |
| Vent Type: | Direct Vent Convertible |
| Temperature Range (F): | 99°F - 167°F |
| BTU (Max): | 190000 |
| BTU (Min): | 11000 |
| PSI Range: | 15-150 psi |
| Height (Inches): | 20.25" |
| Weight (lbs): | 38 lbs |
| Width (Inches): | 13-3/4" |
Questions?
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Call or text 888-757-4774
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Saturday – Sunday
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Compare Similar Products
Brand
Application
Product Type
Installation Type
Fuel Type
Energy Factor
CURRENT ITEM
2-3 Showers
Tankless Heater
Indoor Only
Natural Gas
0.82
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Product Reviews
4.92 out of 90 reviews
100% would recommend this product
5 star
92%
4 star
8%
3 star
0%
2 star
0%
1 star
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Showing 1-10 of 90 reviews
Yes!
This is my second Takagi tankless water heater (first one lasted 15 years). With a tankless water heater (propane or natural gas) you never run out of hot water and it only heats when you need it. Endless hot water for your spa tub, and visiting family can shower one after another using 2 showers. Will never go back to a tank water heater that "cooks" water all the time.
Ken
Missouri
7 years ago
Verified Buyer
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nice unit for propane
We had a sulfur smell coming from our electric tanked hot water. We chose the TK-4 based on reviews and are impressed. Good support and fast delivery from Supplyhouse too.
Ironman Phil
Wayland NY
7 years ago
Verified Buyer
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Great heater
We had a Takagi K3 before it went out and we were pleased with it so we bought the K4 and we where not disappointed. It has more gpm and it's noticable. Would recommend this to anyone!
An
Los Angeles
7 years ago
Verified Buyer
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Quick shipping, excellent packaging
Excellent product, installation straight forward.
Leslie
FL
7 years ago
Verified Buyer
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I will buy this same product again
I have 4 of these tankless heaters at my house. I will buy the same one from you the next time 1 goes out. It changed out with ease. I am so happy with my heater and having hot water again in my kitchen. Great price delivered to my home
Susan
Cornville az
7 years ago
Verified Buyer
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Works GREAT and Quick delivery
Seems as the water is actually hotter (with default 122 deg setting) than with the original 80 gal electric tank type water heater. Was a really good decision.
Bruce
PA
7 years ago
Verified Buyer
Was this review helpful to you?
Great heater and awesome service!
I purchased this heater to replace the 12+ year old TK-3 that is no longer made. ZERO modifications to the water, gas and z-vent exhaust! Ordered at mid day and heater was on my stoop the next afternoon! supplyhouse.com does it again!
Dean C.
Massapequa Park, NY
7 years ago
Verified Buyer
Was this review helpful to you?
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Great product, but do your research
I purchased this product based on its exceptional consumer ratings, price, and application. I did not realize that the necessary venting for my application would cost several hundred dollars more due to its specificity. This is a great unit to mount to an exterior wall and vent through the wall, however in my case venting through the roof required 9 feet of category 3 stainless tubing plus the specific termination kit, all significantly more expensive than PVC. The condensing unit, despite being more expensive would probably have made more sense. That being said, it all went together nicely and works great. With my system running 6gpm from 3 sources, I had plenty of hot water and after 10 minutes, the hottest point in the exhaust venting only reached 130 deg. far. You definitely want to get a softener as well if you have hard water to prolong the life of the unit. In my case, my water hardness killed a coffee pot per year, so I knew it would do the same to this thing. Do to having to run natural gas lines and cutting a hole in the roof, I would rate this an 8 out of 10 for difficulty of installation. Also, you'll see that I taped the seams of the exhaust. This is not required, it was just for peace of mind. Also, supplyhouse.con was exceptional. Their customer service was top notch. Shout out to Colin for his patience and great customer service dealing with a total nube. Also the tech support through Z-vent as well as Takagi made the installation a little easier as well.
Anthony
INDIANA
7 years ago
Verified Buyer
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This is my second TK-4-IN.
My first TK-4-IN water heater was a propane model.NOT CONVERTABLE for NG.
Stevarino
OH
7 years ago
Verified Buyer
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Takagi has been great to us.
Our last model has lasted about 13 years and get this as a replacement. SupplyHouse has easy web commerce and good prices with fast delivery.
Tomjwu
San Jose, CA
8 years ago
Verified Buyer
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Product Q&A
31 Questions31 Questions
Q: Manual says that this unit needs 3/4" gas pipe.. is that ID or OD?
Asked by Isgvl 8 years ago
Add your answer
Verified Reply- SupplyHouse StaffIt would have a 3/4" NPT threaded connection. NPT is a national standard for pipe threads that is generally based on the inside diameter of the pipe.
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Q: Would the TK4 work if there is a power outage?
Asked by Kenny 10 years ago
Add your answer
Verified Reply- SupplyHouse StaffNo, all of the gas tankless units we carry would require power to function.
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- anonymous
Install a ups in line with the ac cord, now ac with power out
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Q: what natural gas pressure regulator is needed for this unit? in the manual the specifics for gas line length and cubic feet is listed but not the pressure. new gas line is being installes for this unit and I want to get the right regulator. any suggestions?
Asked by an7h0ny 10 years ago
Add your answer
Verified Reply- SupplyHouse StaffThe TK-4 requires an inlet gas pressure between 5" and 10.5" WC.
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Q: I am replacing an old Aquastar tankless unit, which is in my kitchen. I am being told that some new systems are extremely noisy, and that I might want to relocate the new unit to the laundry room. How noisy is this unit? Would keeping it in the living space be an issue? Thanks!!
Asked by Vera 10 years ago
Add your answer
Verified Reply- SupplyHouse StaffAccording to Takagi, "Although the water heater is designed to operate with minimal sound, the manufacturer does not recommend installing the unit on a wall adjacent to a bedroom, or a room that is intended for quiet study or meditation, etc."
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Q: I just bought the liquid propane version of the TK-4-IN-LP, and a friend (also licensed plumber) is saying I need a backflow preventer and a vertical condensate drain, and asking if there is a drain in the garage (where is will be housed). I thought this version didn't need drainage because it is a non-condensation (stainless steel vents) system. Your take? Thanks.
Asked by Tom 11 years ago
Add your answer
Verified Reply- SupplyHouse StaffWhile not a condensing unit, Category III appliances do vent lower temperature exhaust which is at risk of condensing. As such, a backflow preventer and drain tee are necessary to catch and drain any condensation that does occur, to keep it from entering the heat exchanger.
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Q: I am replacing a TK-3. Are the plumbing attachments located in same positions as the TK-3?
Asked by GAF 11 years ago
Add your answer
Verified Reply- SupplyHouse StaffYes, they are in the same position.
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Q: Radiant Heat ??
Asked by Debra 11 years ago
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Verified Reply- SupplyHouse StaffThis unit is suitable for use as a heat source for radiant heat, so long as your local code allows it.
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Q: We have natural gas at this time. If we buy the natural gas water heater and later on we end up with LP gas can the unit be converted to LP?
Asked by Jim 11 years ago
Add your answer
Verified Reply- SupplyHouse StaffCurrently, Takagi does not offer conversion kits for any of their units. It is possible they may offer them in the future, but at the moment we wold advise against planning on a conversion if you anticipate you will need to.
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Q: Can this be used on hidronic heating system?
Asked by Fernando 11 years ago
Add your answer
Verified Reply- SupplyHouse StaffAccording to Takagi, their units are "suitable for potable water heating and space-heating. Please refer to local codes for space-heating compliance."
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Q: I have 1/2" propane gas supply line. Is this adequate for the TK-4-IN Takagi Tankless Indoor Water Heater (Propane)?
Asked by Fred 11 years ago
Add your answer
Verified Reply- Supplyhouse StaffYou would need to know the inches of WC, Takagi requires a minimum of 8" WC for LP.
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