Natural Gas Tankless Water Heater, MIZUDO Indoor Installation Max 5.1 GPM 120,000 BTU On Demand Hot Water Heater, CSA Certified Constant Temp High Power for 2-3 Fixtures Big Family or Business, Gen 2
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Material Type: 5.1 GPM, 120,000 BTU, Indoor
Style: Natural Gas
Features
- Upgraded Temp Control: Mizudo Gen 2 water heater will self-modulate water temp by the interaction between the gas proportional valve, water volume servo and built-in chip to ensure that the temperature difference is within 1F, provide you with a constant temperature and comfortable bathing experience
- Endless Huge Hot Water: Tankless water heater delivers up to 5.1 GPM at 120000 BTU, ideal for running 3 showers simultaneously in big house with 2-3 bathrooms; Only sonsumes gas when during using, no standby waste, will save up to 20% gas bills
- Quality & Compliance: All our tankless water heaters gas are UL listed and CSA certified meeting all US safety codes. We also provide 2-year support for the whole unit and 5-year support for the oxygen-free copper heat exchanger
- Safety Protections: This natural gas tankless water heater is provided with windproof, waterproof and protections of leakage, overheate, anti-freeze, dry-combution and so on. Extend service life and improve safety, prevents 80% of common tankless failures
- Product Information: The gas tankless water heater is 22.76 x 14.57 x 7.0 inches, support indoor installation only; Natural gas powered and LED screen control. Uses 120V power and 3/4" NPT connectors, compatible with most US homes. UEF>0.81 exceeds DOE baseline
Brand: MIZUDO
Product Dimensions: 14.57"W x 22.76"H
Special Feature: 2 Years Support for Whole Unit, 5 Years Support for Heat Exchanger, Automatic Anti-Freezing Protection, CSA Certificated, Upgraded Temp Control See more
Color: White
Wattage: 37 Watt-hours
Brand: MIZUDO
Product Dimensions: 14.57"W x 22.76"H
Special Feature: 2 Years Support for Whole Unit, 5 Years Support for Heat Exchanger, Automatic Anti-Freezing Protection, CSA Certificated, Upgraded Temp Control
Color: White
Wattage: 37 Watt-hours
Voltage: 120 Volts (AC)
Maximum Flow Rate: 5.1 Gallons Per Minute
Heat Output: 120000 BTU per Hour per Foot per Degree Fahrenheit
Efficiency: High
Maximum Operating Pressure: 150 Pound per Square Inch
Mounting Type: Wall
Is Electric: No
Manufacturer: Mizudo
Item Depth: 7 inches
Item Weight: 29.9 pounds
Item model number: FDG-CS120BW-NG
Item Package Quantity: 1
Special Features: 2 Years Support for Whole Unit, 5 Years Support for Heat Exchanger, Automatic Anti-Freezing Protection, CSA Certificated, Upgraded Temp Control
Included Components: Gas Water Hetaer x 1, Manual x 1, Perforated Paper x 1, Assembly Kit x 1, Warranty Card x 1
Batteries Included?: No
Batteries Required?: No
Date First Available: January 13, 2024
Frequently asked questions
This product is currently out of stock. Please check back later for shipping info.
This item is non-returnable:
Non-returnable. Transportation of this item is subject to hazardous materials regulation
View our full returns policy here.
Non-returnable. Transportation of this item is subject to hazardous materials regulation
View our full returns policy here.
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Top Amazon Reviews
Material Type: 5.1 GPM, 120,000 BTU, Indoor
Style: Propane Gas
I installed this in the cabin we live in about a month ago and so far it's been working well for us. The distance from the heater to the various taps is fairly short and there is a bit of a lag getting hot water to the outlets,but I believe that is more of a result of the "water saving" fixtures we are stuck with these days and their flow restrictive nature. Water temp fluctuations have been minimal. Though we have noticed some due to the lower temp of the incoming water to the heater after the water has run for a period of time. We have very cold water from our well. The unit is a little noisy,but that is far from our concerns. My only real concern is the water heater cycling when running the washing machine when set to a warm wash temperature. It runs for such a short period that the water doesn't really get an opportunity to heat and I feel like the rapid cycling is probably not good for the heater. I feel this is more of an issue with the washer than the heater. Our solution was to run the washer on a hot setting and reduce the temperature on the water heater. Right now we just have a whole house filter installed in the inlet. We did have a Water Drop scale inhibitor installed,but it leaked and had to return it to Amazon for a replacement. Definitely on the homestead priority list as we have very hard water. All in all we have been pretty happy with the heater. Super easy install except for cutting a hole in the logs for the vent.
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Reviewed in the United States on May 23, 2024 by Jeffz Jeffz
Material Type: 4.0 GPM, 90,000 BTU, Indoor
Style: Natural Gas
I cannot say enough good about this water heater. Had zero problems installing, and after several months of using it our gas bill is about 1/3 for the same hot water usage. There's always hot water, no matter how many people are taking showers
Reviewed in the United States on July 16, 2025 by Iz, Esquire
Material Type: 5.1 GPM, 120,000 BTU, Indoor
Style: Natural Gas
The first one that I ordered had some electrical defects when I hooked it up. The system continued to beep on and off constantly and would not work. I filed for a replacement through Amazon and it was a good interaction. I received a replacement model which works perfect!! It's quiet and heats water in seconds.. I'd buy again!
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Reviewed in the United States on December 20, 2024 by Brett
Material Type: 4.0 GPM, 90,000 BTU, Indoor
Style: Propane Gas
Excellent price simple and easy install highly recommend
Reviewed in the United States on July 16, 2025 by t.l.wilson
Material Type: 4.0 GPM, 90,000 BTU, Indoor
Style: Natural Gas
I'm sure it's probably a fine product, just shouldn't be sold for Coloradians. Our plumber wouldn't install it as it indicates it's not to be used over 2000 ft in elevation. We're nearly 4000 ft above sea level. That's kind of important enough to list on the seller's portal. Had to return it.
Reviewed in the United States on May 29, 2024 by Dennis McDaniel Jr
Material Type: 4.0 GPM, 90,000 BTU, Indoor
Style: Natural Gas
I have a small 1200ft house with just my fiancé and I. This works great for our needs! Do research on the install as it’s not your normal water heater connections. I placed a larger 4” metal dryer vent hood through the exterior wall then routed the smaller vent pipe for the unit through it (vent pipe is smaller, 3”, so it doesn’t touch the homes walls). Water pressure is great, heat is very good, the only caveat is if your turning on and off your water (say washing your face) it’ll have to shoot out the cold water from restarting before it gets back to hot. Overall great purchase as it also should save money from not having a lite water heater 24/7. If you have hard water (I don’t) then maybe install a filter in line or flush your unit once a year with vinegar.
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Reviewed in the United States on November 20, 2024 by Jordan F. Jordan F.
Material Type: 5.1 GPM, 120,000 BTU, Outdoor
Style: Propane Gas
The media could not be loaded. Update 4 I hate giving one star reviews especially if the company has good customer support, so I changed to 3 stars. They send me a new unit and if you are in a warm climate this would probably work for you. Update 3 Water is pouring out of heater as it thaws so the automatic anti freeze does not work! Temperatures got down to 24 F and the heater is ruined! It lasted about 2 weeks. The pic I posted shows the instructions for freezing temperatures, this is proof it’s falsely advertised and if that is the case I wonder how long it would have lasted in say Florida, what a joke! Update 2 The temperature outside is 24 and the thermostat is showing the unit is 32. I do not recommend this unit for people in locations that might freeze. Understand that they state that the unit is not covered by freezing so basically they are lying about their product. That’s my last word on this heater. Update: I gave them another star for reaching out and asking if I wanted to exchange for an inside model. With the heavy brass valves now insulated, the unit did not freeze at 22 degrees, but that was also with a faucet left to drip. The thermostat still show the unit getting down as low as 35 and then it bounces up to 39 so I guess it’s trying to maintain temperature. For the price it’s a decent value and if you live in warmer climates it’s a good value. As far as wind and rain, the heater has performed well. I’ve only had this installed for a couple of days, Warranty states freezing is not covered but the unit is supposed to keep itself from doing that. In the first 2 days I noticed the unit maintained 44 F I was starting to feel relaxed, good thing I checked one last time! Went out to open drain lines and they were already froze. Took a torch to the valves and that got the water moving, heater fired up. Cut off water and let it drain, I no longer trust this heater will keep itself from freezing. Unless you live where it doesn’t freeze, don’t buy, especially don’t buy if your temps go below 28 which is a pretty light freeze. When it’s not freezing it seems to work fine but it’s only been a couple of days. 2 stars because it’s worthless to me, should have just purchased an interior unit and vented it!
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Reviewed in the United States on January 10, 2025 by Jorge Pease Jorge Pease
Material Type: 5.1 GPM, 120,000 BTU, Outdoor
Style: Propane Gas
It's not as fast as what it was replacing, but I like it's build and finish. Another thing I like is that the water temp is constantly adjusting to the set temperature. The wired remote makes it easy to use. The display on the controller tells you the water inlet temp and the outlet temp. When it shuts down, the fan will continue to run to cool it down quickly. The water heater is very well made and seems to be very efficient.
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Reviewed in the United States on December 29, 2024 by Michael R Glatfelter Jr