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T-K4-OS-LP has been discontinued
Discontinued May 10, 2019
This product was discontinued by the manufacturer.
MANUALS (4)
This item replaces: T-K3-OS-LP
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Direct Replacement:
Series 200 Ultra Low-NOx Non-Condensing Outdoor Tankless Water Heater (8 GPM, NG/LP)
Product Highlights
–
Propane
8 MAX GPM
Outdoor 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:
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.
The T-K4-OS has a built-in power venting system and was designed specifically for outdoor installations. The T-K4-OS does not require any additional Category III venting or vent caps, making installation one step easier for installers.
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: 0.83
- Inlet Gas Pressure: Min: 8.0" W.C. / Max 14.0" W.C.
- Dimensions: 20.3" H x 13.8" W x 8.5" D
- No Venting Required
- Electric Ignition
Specs
–
| Application: | 2-3 Showers |
|---|---|
| Product Type: | Tankless Heater |
| Fuel Type: | Propane |
| Installation Type: | Outdoor Only |
| Energy Factor: | 0.83 |
| Height: | 20.3" |
| Inlet Gas Pressure: | 8.0"-14.0"W.C. 3.7-4.0"W.C. |
| Width: | 13.8" |
| Depth (Inches): | 8-1/2" 9-1/2" |
| Energy Star Rated: | No |
| Max Flow (GPM): | 8 |
| BTU (Min): | 11000 |
| BTU (Max): | 190000 |
| Voltage: | 120v |
| Height (Inches): | 20.25" |
| Gas Input: | 11000-190000 BTU/h |
| Width (Inches): | 13-3/4" |
| Water Connection: | 3/4" |
| Gas Connection: | 3/4" |
| Temperature Range (F): | 99°F - 167°F |
| PSI Range: | 15-150 psi |
| Weight (lbs): | 38 lbs |
Questions?
Speak with a real person who will go out of the way to help!
Call or text 888-757-4774
Monday – Thursday
8am–7:45pm
Friday
9am–7:45pm
Saturday – Sunday
9am–5:45pm
You May Also Need
75 Replacement Parts
Filter Plug, 100074381
SKU: 100074381
TakagiKit, Rod, Holder, 100074221
SKU: 100074221
AO Smith310 Indoor/Outdoor PCB Kit, 100074342
SKU: 100074342
TakagiIgniter Rod, 100074222
SKU: 100074222
TakagiRod Cap, 100074223
SKU: 100074223
AO SmithKit, Cable, Igniter, High Voltage, 100074224
SKU: 100074224
AO SmithOutlet Drain Plug, 100074383
SKU: 100074383
TakagiKit, Heater, 100074384
SKU: 100074384
AO SmithKit, Outlet, Heat, 100074263
SKU: 100074263
AO SmithFlame Rod, 100074220
SKU: 100074220
TakagiHeat Exchanger Assembly (T-K4-OS), 100074341
SKU: 100074341
TakagiManifold Gasket, A, 100074229
SKU: 100074229
TakagiPressure Port, 100074227
SKU: 100074227
TakagiFan Motor, 100074228
SKU: 100074228
TakagiKit, Ring, Silicon, 100074390
SKU: 100074390
AO SmithKit, Wire, Gas Valve, 100074391
SKU: 100074391
AO SmithKit, Wire, Flame Rod, 100074392
SKU: 100074392
AO SmithKit, Plate, Surge Box, 100074397
SKU: 100074397
AO Smith
Need help finding a replacement part?
Fill out the part request form and someone will get back to you shortly.
PART REQUEST FORM
Product Reviews
4.65 out of 20 reviews
100% would recommend this product
5 star
70%
4 star
25%
3 star
5%
2 star
0%
1 star
0%
Most Liked Positive Review
Great Outside Tankless..get all parts
Very neat compact OUT DOOR unit. No venting to buy or install. Just don't install directly under roof overhang. Be sure to buy the Recess Box that completely houses the tankless unit between 16" on center studs (box is 14.2" wide). However, the depth is 9", that's greater than 2x4 or 2x6 wall if house is sided with OSB and HardiePlank. Most youtube vids show mount on exterior wall.... BAD IDEA, easy to see and steal. Recess box is a must and also use Isolation Valves so you can service/replace tankless if necessary without cutting copper pipes. These two items, in addition to the tankless, really add up to the price "$$" when compared to traditional 30g/50g water tanks.
One last thing. The position of the valves in the recess box are NOT optimal due to close proximity of the cold & hot water connection points on TK-4 and the lack of space around the valves forcing you to face the Pressure Relief valve to the right to function. To bad you can't see a picture of how it all installs. One youtube vid "Descaliing a Noritz tankless water heater" shows great valve setup but unfortunately this will NOT work on Takagi installed in Recess Box because no room in box to face pressure relief valve to the left.
VS
Most Liked Negative Review
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Received broken
In the end, it works and the one I had previously worked reliably in harsh conditions for years but disappointingly this one arrived perfectly packaged and brand new but with a malfunctioning main computer board which kept the unit from operating. It took several calls and a few hours on the phone with the manufacturer to diagnose but eventually they did determine cause and fed ex'ed a new board to repair. Works fine now
Showing 1-10 of 20 reviews
Great water heater
When building our home there was no question we would go tankless.... which one took a while. Lots of research later we order this. We have been in the house almost 2 months and LOVE it! No issues installing. We have a large shower and typically run both shower heads at the same time. No issues with hot water!!
GaPeachNanny
NW Georgia
7 years ago
Verified Buyer
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Best all around price and service
Searched far and wide for this unit. Supply House had the best price available and with free shipping.
SloEz
Albuquerque NM
8 years ago
Verified Buyer
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Straight forward, easy installation.
Light weight, easy to install, easy to follow instructions, works fine. Overall great product. This was my first 'external' install that ended up being a flush install. The design of this unit made installation modifications manageable and only frame out and a piping access cover panel were required, basically half day labor costs to customer.
JohnEd
N.E. Texas
8 years ago
Verified Buyer
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good price, good service
good price, good service
merrill
hilton head, sc
8 years ago
Verified Buyer
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Found this item at a good price.
Was shipped quickly and arrived ahead of schedule. Was not difficult to install and believe it will be a good product for quite a few years.
Davy
Crystal Springs MS
8 years ago
Verified Buyer
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My first Takagi lsted 14 years without an issue.
Very dependable. Unfortunately you have to wait a bit for hot water compared to a tank heater, especially if your faucet or appliance is a distance form the unit.
Pbrides
South Florida
8 years ago
Verified Buyer
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2nd Takagi Tankless water heater
After the confusion of Outdoor vs Indoor (we needed an indoor model) was settled my new TK-4 was installed without any hitches. If it works as good as the TK-3 we will be more than happy. First, you have endless hot water no matter how many are using it. Second, the reduction in propane use is substantial and pays for the cost difference especially with the affordable Takagi brand. It does require annual maintenance but it is well worth the minor trouble.
Charley
Spring Branch, Tx
8 years ago
Verified Buyer
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I would buy this product over and over this is my 4th time
Never give any problem worked 13 year nonstop
Roman Hovhannisyan
LA
9 years ago
Verified Buyer
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Received broken
In the end, it works and the one I had previously worked reliably in harsh conditions for years but disappointingly this one arrived perfectly packaged and brand new but with a malfunctioning main computer board which kept the unit from operating. It took several calls and a few hours on the phone with the manufacturer to diagnose but eventually they did determine cause and fed ex'ed a new board to repair. Works fine now
Randy
Florida Keys
9 years ago
Verified Buyer
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Excellent
I'm an architect and a DIY kind of guy.
Great value product and reliable source.
Istvan Peteranecz
Saint Petersburg
9 years ago
Verified Buyer
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Product Q&A
3 Questions3 Questions
Q: Could this be used as a pool heater?
Asked by Ron 11 years ago
Add your answer
Verified Reply- SupplyHouse StaffNo, as per the manual, "Only potable water or potable water / glycol mixtures can be used with this water heater. Do not introduce pool or spa water, or any chemically treated water into the water heater."
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Q: It says OS --- and the photo shows a vent facing up.... what is the venting for the outside one?
Asked by Keith 12 years ago
Add your answer
Verified Reply- SupplyHouse StaffThe TK-4-OS vents horizontally from a port near the top of the unit. The illustration in the manual is not correct. No other venting attachments are required.
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-
That's Odd. My OS unit direct vents form the front Panel at the top of the unit. So it basically blows vented exhaust horizontally out from the upper most part of the face Panel. There is not even a port on the top as an option, so I don't know why they show it the picture. They are apparently using a stock photo for all models which is oddly inaccurate. Check out page 45 of the manual (on the product page) It shows a picture of al of the different models, this will show the vent port.
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The unit vents out the top, front vent. You might be mistaking the mounting flange on top of the unit for a vent. I have this unit mounted in the available outside receptacle/box. The unit supplies all hot water for three baths , laundry, kitchen, and radiant heat for 1150 sq/ft house. I could not be more satisfied. Ned Krabacher
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Q: What are other accessories required for instalment?
Asked by Ann 15 years ago
Add your answer
Verified Reply- PexSupply StaffYou will need a gas valve, gas line, pressure relief valve, ball valves, etc.
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