Best Forimo Tankless Water Heaters: 8 Models Compared
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This guide compares 8 models of best forimo tankless water heaters to help you find the right unit. Forimo offers compact indoor natural gas and propane heaters, plus an RV-specific propane model. The Forimo 4.74 GPM Indoor Natural Gas Water Heater leads this list because it delivers 123,000 BTU/hr for multi-fixture indoor use. Our selections are based strictly on the published specifications for each listing. We focus on flow rates, BTU output, and physical dimensions. This approach ensures you get practical data for your installation needs.
Quick picks
Our 8 picks
Forimo 4.74 GPM Indoor Natural Gas Water Heater
Best for: indoor multi-fixture natural gas setups
- Fuel Type
- Natural Gas
- Flow Rate
- 4.74 GPM
- BTU
- 123,000 BTU/hr
- Installation Location
- Indoor
- Temperature Control
- Fahrenheit digital display
- Dimensions
- 22 x 13.8 x 13.8 inches
View on Amazon: Forimo 4.74 GPM Indoor Natural Gas Water Heater
This indoor natural gas tankless water heater delivers up to 4.74 GPM with a maximum output of 123,000 BTU per hour. It connects via standard 1/2-inch NPT fittings and vents through a 2.3-inch exhaust pipe. Built with a copper heat exchanger and a digital display, it provides enough capacity to run two to three fixtures at once. It suits you if you need whole-home indoor natural gas heating.
Pros
- Maximum output of 123,000 BTU/hr delivers 4.74 GPM flow rate
- Oxygen-free copper water tank and stainless steel exterior
- LED digital display shows temperature in Fahrenheit
- Standard 1/2-inch NPT connections for gas and water lines
Cons
- Requires minimum water pressure of 29 PSI to operate
- Indoor installation requires dedicated 2.3-inch outdoor venting
Good fit if
- You have an indoor natural gas supply line.
- You need to supply hot water to two or three fixtures simultaneously.
- You maintain incoming water pressure of at least 29 PSI.
Skip if
- You use liquid propane rather than natural gas.
- You lack exterior access for the 2.3-inch exhaust vent pipe.
Verdict: Forimo 4.74 GPM Indoor Natural Gas Water Heater offers 123,000 BTU/hr to supply up to three fixtures concurrently. It provides dependable indoor natural gas heating if your home meets its 29 PSI minimum pressure requirement.
Forimo 16L 4.21 GPM Indoor Propane Heater
Best for: indoor multi-fixture liquid propane setups
- Fuel Type
- Propane (LPG)
- Flow Rate
- 4.21 GPM
- BTU
- 81,888 BTU/hour
- Installation Location
- Indoor
- Temperature Control
- Fahrenheit digital display
- Dimensions
- 21.7 x 13.8 x 13.8 inches
This indoor tankless water heater runs exclusively on liquid propane and delivers up to 4.21 gallons per minute with an 81,888 BTU per hour rating. Built with an oxygen-free copper heat exchanger and a digital display, it provides steady hot water for two to three fixtures at once. It suits you if you need a compact indoor propane unit for a home, cabin, or apartment with low water pressure.
Pros
- Flow rate of 4.21 GPM supports 2 to 3 simultaneous outlets
- Operates with minimum water pressure of 3.6 PSI
- Includes 2.4-inch horizontal vent pipe for installation
- Durable oxygen-free copper heat exchanger and stainless steel body
Cons
- Operates exclusively on liquid propane, not natural gas
- Requires manual draining via relief valve during freezing weather
Good fit if
- You run propane and need hot water across 2 to 3 fixtures simultaneously.
- You have low water supply pressure down to 3.6 PSI.
- You need an indoor heater that includes horizontal venting hardware.
Skip if
- You have a natural gas line rather than propane.
- You require more than 4.21 GPM of simultaneous water flow.
Verdict: Forimo 16L 4.21 GPM Indoor Propane Heater delivers dependable 81,888 BTU performance for multi-point indoor use on liquid propane. Its low 3.6 PSI activation threshold makes it practical for cabins and smaller households.
Forimo 4.74 GPM Natural Gas Tankless Water Heater
Best for: indoor multi-fixture natural gas home setups
- Fuel Type
- Natural Gas (LNG)
- Flow Rate
- 4.74 GPM
- BTU
- 81,888 BTU/hour
- Installation Location
- Indoor
- Temperature Control
- Fahrenheit digital display
- Dimensions
- 21.7 x 13.8 x 13.8 inches
View on Amazon: Forimo 4.74 GPM Natural Gas Tankless Water Heater
This indoor tankless water heater runs exclusively on natural gas and delivers up to 4.74 gallons per minute with an 81,888 BTU per hour rating. It operates with water pressures as low as 3.6 PSI and includes a 2.4-inch horizontal vent pipe. If you need to supply two to three plumbing fixtures at once in a home or cabin without installing an expansion tank, this unit fits your setup.
Pros
- Delivers up to 4.74 GPM flow rate powered by 81,888 BTU/hour
- Includes a 2.4-inch horizontal vent pipe and 1/2-inch NPT fittings
- Operates with a low water activation threshold of 3.6 PSI
- Constructed with an oxygen-free copper heat exchanger and stainless steel housing
Cons
- Compatible only with natural gas lines, not propane
- Requires proper horizontal wall venting and indoor installation
- Must be manually drained via the relief valve during freezing weather when idle
Good fit if
- You have an indoor natural gas hookup and want to supply 2 to 3 fixtures at once.
- You deal with low incoming water pressure down to 3.6 PSI.
Skip if
- You use liquid propane fuel rather than natural gas.
- You need an outdoor-mounted unit that does not require indoor venting.
Verdict: Forimo 18L 4.74 GPM Indoor Natural Gas Water Heater provides 81,888 BTU/hour of demand heating capacity for multi-outlet indoor setups. Its 4.74 GPM flow rate makes it the highest-capacity natural gas option across this 8-model guide.
Forimo 16L Indoor Propane Tankless Water Heater
Best for: small homes and cabins running on propane
- Fuel Type
- Propane (LPG)
- Flow Rate
- 4.21 GPM
- BTU
- 81,888 BTU/hour
- Installation Location
- Indoor
- Temperature Control
- Fahrenheit digital display
- Dimensions
- 21.7 x 13.8 x 13.8 inches
View on Amazon: Forimo 16L Indoor Propane Tankless Water Heater
This indoor propane tankless water heater delivers up to 4.21 GPM with an 81,888 BTU per hour heat output. It requires a minimum water pressure of 3.6 PSI and operates on liquid propane. The unit includes a 2.4-inch horizontal vent pipe and standard 1/2-inch NPT fittings. If you need steady hot water across two to three fixtures in a cabin, apartment, or small home, this model fits your setup.
Pros
- Flow rate of 4.21 GPM supports two to three simultaneous fixtures
- Operates with water pressure as low as 3.6 PSI
- Includes horizontal 2.4-inch vent pipe for indoor exhaust setup
- Oxygen-free copper heat exchanger with stainless steel body
Cons
- Operates strictly on propane with no natural gas compatibility
- Requires manual draining via relief valve in freezing temperatures
- Delivers less output than the 18L models in the lineup
Good fit if
- You use liquid propane to power your home, apartment, or cabin.
- You need to supply hot water to two or three points at once.
- You operate on a low water pressure supply down to 3.6 PSI.
Skip if
- You require a natural gas connection rather than propane.
- You need more than 4.21 GPM for high concurrent water usage.
Verdict: Forimo 16L Indoor Propane Tankless Water Heater delivers 81,888 BTU per hour and a 4.21 GPM flow rate for indoor propane setups. It is a practical mid-size option if you need low-pressure startup and included venting hardware.
Forimo 18L Indoor Propane Tankless Heater
Best for: indoor propane setups needing multi-fixture flow
- Fuel Type
- Propane
- Flow Rate
- 4.74 GPM
- BTU
- 68,000 BTU/hr
- Installation Location
- Indoor
- Temperature Control
- 86°F-167°F
- Dimensions
- 25.4 x 14.4 x 14.4 inches
This indoor tankless water heater runs on propane and delivers up to 4.74 gallons per minute with a 68,000 BTU maximum output. You get digital temperature control between 86°F and 167°F, standard 1/2-inch NPT fittings, and an included 2.5-inch horizontal vent pipe. It requires 3.6 PSI of water pressure to activate, making it suitable if you need multi-fixture hot water in a cabin or home with liquid propane.
Pros
- Delivers up to 4.74 GPM flow rate at 68,000 BTU
- Activates at a low water pressure of 3.6 PSI
- Adjustable temperature range from 86°F to 167°F with LED display
- Includes 2.5-inch horizontal vent pipe and standard 1/2-inch NPT connections
Cons
- Operates strictly on propane and cannot use natural gas
- Requires manual drainage via relief valve during freezing weather when idle
Good fit if
- You run a liquid propane supply for your home or cabin.
- You need 4.74 GPM to supply two to three fixtures at once.
- You have low incoming water pressure down to 3.6 PSI.
Skip if
- You have a natural gas hookup instead of propane.
- You need an outdoor unit that does not require horizontal flue venting.
Verdict: Forimo 18L Indoor Propane Tankless Water Heater provides 4.74 GPM capacity and reliable 68,000 BTU heating for indoor, propane-fueled installations.
Forimo 15-Inch RV Propane Tankless Water Heater
Best for: RV and camper off-grid hot water setups
- Fuel Type
- Propane
- Flow Rate
- 3.9 GPM
- BTU
- 61,000 BTU/hr
- Voltage
- 12V DC
- Dimensions
- 15 x 15 x 15 inches
- Use
- RV
View on Amazon: Forimo 15-Inch RV Propane Tankless Water Heater
This Forimo propane tankless water heater is built for mobile setups like RVs, campers, and yachts. It runs on a 12-volt DC power connection and delivers up to 3.9 GPM with a 61,000 BTU per hour rating. Its 15-inch cubic frame fits compact spaces and requires 3.6 PSI of water pressure to activate. You get a digital remote controller and an included shower kit for direct mobile installation.
Pros
- Delivers up to 3.9 GPM with 61,000 BTU/hr heating capacity
- Operates on standard 12V DC mobile electrical systems
- Activates with a low water pressure requirement of 3.6 PSI
- Includes digital remote control, plumbing adapter, and shower kit
Cons
- Lower 61,000 BTU rating compared to larger indoor models
- Requires a 12V DC power source instead of standard household AC
- Requires proper exterior ventilation and exhaust space
Good fit if
- You need a compact 15x15x15-inch propane heater for an RV, camper, or yacht.
- You have a 12V DC power source and low water pressure down to 3.6 PSI.
- You want an included shower kit and digital temperature controller.
Skip if
- You need a stationary indoor water heater powered by standard household AC.
- You require a natural gas connection instead of propane.
Verdict: Forimo 15-Inch RV Propane Tankless Water Heater provides on-demand hot water for mobile setups using 12V DC power and liquid propane. Its 3.9 GPM capacity and 3.6 PSI minimum activation make it an effective option for campers and travel trailers.
Forimo 4.21 GPM Natural Gas Tankless Water Heater
Best for: indoor natural gas setups with multiple fixtures
- Fuel Type
- Natural Gas
- Flow Rate
- 4.21 GPM
- BTU
- 68,000 BTU/hr
- Installation Location
- Indoor
- Temperature Control
- 86°F-167°F
- Dimensions
- 14.4"W x 4.72"H x 25.4"L
View on Amazon: Forimo 4.21 GPM Natural Gas Tankless Water Heater
This indoor tankless water heater runs on natural gas and delivers up to 4.21 GPM of hot water with a 68,000 BTU per hour rating. It features a digital display with temperature control from 86°F to 167°F and activates at 3.6 PSI of water pressure. If you need steady indoor hot water for two to three fixtures in a home, cabin, or apartment, this compact unit fits your setup.
Pros
- Delivers up to 4.21 GPM with a 68,000 BTU/hr heat rating
- Activates at a low water pressure of 3.6 PSI
- Adjustable digital temperature range from 86°F to 167°F
- Comes with a 2.5-inch horizontal vent pipe and 1/2-inch NPT fittings
Cons
- Operates exclusively on natural gas with no propane support
- Requires manual drainage via the pressure relief valve during freezing weather
Good fit if
- You have a natural gas supply line and need hot water for two to three indoor points.
- You deal with low household water pressure down to 3.6 PSI.
- You want an indoor unit that includes its own horizontal vent pipe.
Skip if
- You require a liquid propane water heater.
- You need higher flow rates above 4.21 GPM for high-demand simultaneous usage.
Verdict: Forimo 4.21 GPM Natural Gas Tankless Water Heater delivers 68,000 BTU/hr for up to three fixtures using natural gas. It gives you flexible 86°F to 167°F temperature adjustments and an included horizontal vent pipe.
Forimo 4.74 GPM 18L Indoor Natural Gas Tankless Heater
Best for: homes with natural gas running multiple fixtures
- Fuel Type
- Natural Gas (LNG)
- Flow Rate
- 4.74 GPM
- BTU
- 81,888 BTU/hour
- Installation Location
- Indoor
- Temperature Control
- Fahrenheit digital display
- Dimensions
- 21.7 x 13.8 x 13.8 inches
View on Amazon: Forimo 4.74 GPM 18L Indoor Natural Gas Tankless Heater
This indoor natural gas tankless water heater supplies up to 4.74 GPM with an 81,888 BTU/hour burner. It uses standard 1/2-inch NPT fittings, activates at 3.6 PSI water pressure, and includes a 2.4-inch horizontal vent pipe. An LED digital display controls temperatures up to 167°F (75°C). It suits your home, cabin, or apartment if you run two to three fixtures simultaneously on a dedicated natural gas line.
Pros
- Delivers up to 4.74 GPM for two to three simultaneous outlets
- Low activation threshold requiring only 3.6 PSI water pressure
- Includes a 2.4-inch horizontal vent pipe and standard 1/2-inch NPT connections
- Equipped with an oxygen-free copper heat exchanger and digital LED controls
Cons
- Operates exclusively on natural gas with no propane compatibility
- Requires manual draining via relief valve in freezing weather when idle
Good fit if
- You have an active indoor natural gas hookup.
- You need to serve two to three fixtures simultaneously with up to 4.74 GPM.
- You operate plumbing with low water pressure down to 3.6 PSI.
Skip if
- You use liquid propane rather than piped natural gas.
- You lack wall access for horizontal flue venting.
Verdict: Forimo 4.74 GPM 18L Indoor Natural Gas Tankless Heater delivers solid multi-tap flow for homes connected to natural gas. Its included horizontal exhaust pipe and low-pressure activation make it practical for indoor utility setups.
Specifications side by side
| Spec | Forimo 4.74 GPM Indoor Natural Gas Water Heater | Forimo 16L 4.21 GPM Indoor Propane Heater | Forimo 4.74 GPM Natural Gas Tankless Water Heater | Forimo 16L Indoor Propane Tankless Water Heater | Forimo 18L Indoor Propane Tankless Heater | Forimo 15-Inch RV Propane Tankless Water Heater | Forimo 4.21 GPM Natural Gas Tankless Water Heater | Forimo 4.74 GPM 18L Indoor Natural Gas Tankless Heater |
|---|---|---|---|---|---|---|---|---|
| Fuel Type | Natural Gas | Propane (LPG) | Natural Gas (LNG) | Propane (LPG) | Propane | Propane | Natural Gas | Natural Gas (LNG) |
| Flow Rate | 4.74 GPM | 4.21 GPM | 4.74 GPM | 4.21 GPM | 4.74 GPM | 3.9 GPM | 4.21 GPM | 4.74 GPM |
| BTU | 123,000 BTU/hr | 81,888 BTU/hour | 81,888 BTU/hour | 81,888 BTU/hour | 68,000 BTU/hr | 61,000 BTU/hr | 68,000 BTU/hr | 81,888 BTU/hour |
| Installation Location | Indoor | Indoor | Indoor | Indoor | Indoor | not specified | Indoor | Indoor |
| Voltage | not specified | not specified | not specified | not specified | not specified | 12V DC | not specified | not specified |
| Temperature Control | Fahrenheit digital display | Fahrenheit digital display | Fahrenheit digital display | Fahrenheit digital display | 86°F-167°F | not specified | 86°F-167°F | Fahrenheit digital display |
| Dimensions | 22 x 13.8 x 13.8 inches | 21.7 x 13.8 x 13.8 inches | 21.7 x 13.8 x 13.8 inches | 21.7 x 13.8 x 13.8 inches | 25.4 x 14.4 x 14.4 inches | 15 x 15 x 15 inches | 14.4"W x 4.72"H x 25.4"L | 21.7 x 13.8 x 13.8 inches |
| Use | not specified | not specified | not specified | not specified | not specified | RV | not specified | not specified |
| Features | Digital Display | Digital Display | Digital Display | Digital Display | Digital Display | not specified | Digital Display | Digital Display |
| Weight | not specified | 22.9 pounds | not specified | 21.9 pounds | not specified | not specified | 23 pounds | 23.2 pounds |
| Color | Black | Black | Black(18L-Natural Gas) | Black(16L-Propane) | Black | White | Black | Black |
| Model | HW-FM-18-LNG | CT1312-HWRSQ | CT1414-HWRSQ | CT1412-HWRSQ | HWRSQ-18L-LPG-2 | RV-white-9L | Tankless Water Heater-01 | CT1314-HWRSQ |
| Size | not specified | 16L | 18L | 16L | not specified | not specified | not specified | 18L |
The Forimo Lineup At A Glance
Most Forimo heaters are indoor units designed for natural gas or propane. The Forimo 4.74 GPM Indoor Natural Gas Water Heater leads with high output for multi-fixture use. The Forimo 16L 4.21 GPM Indoor Propane Heater offers a low activation threshold for smaller homes. Both feature digital displays and compact black casings. These models suit standard residential setups where reliable indoor heating is the priority. You get consistent performance for kitchen and bathroom sinks.
The Forimo 15-Inch RV Propane Tankless Water Heater stands apart as a mobile solution. It uses 12V DC power and propane for campers or travel trailers. Its compact cubic design fits tight spaces. Other models, like the Forimo 4.21 GPM Natural Gas Tankless Water Heater, include horizontal vent pipes. Choose based on your fuel source and whether you need stationary or mobile hot water.
Where Forimo Fits Your Needs
Forimo’s range covers indoor natural gas and propane units, plus one RV model. Sizes vary from 15-inch cubes for campers to taller rectangular boxes for homes. Flow rates span 3.9 to 4.74 GPM. All listed indoor models feature digital displays. You will not find outdoor units or electric options here. The brand focuses on compact, vented gas heaters. If you need a large commercial unit or outdoor installation, Forimo does not offer those. Stick to their indoor gas or propane lines for residential or mobile use.
If you also compare home fitness equipment, you can evaluate tank capacities across the best water rowers.
How to Choose the Right Forimo Model
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Match Fuel Type to Supply
You must select the correct fuel source for your home’s infrastructure. Natural gas models, such as the Forimo 4.74 GPM Indoor Natural Gas Water Heater, require a connected gas line. Propane units, like the Forimo 16L 4.21 GPM Indoor Propane Heater, use liquid propane tanks. Using the wrong fuel type prevents the unit from operating. Check your existing utility connections before purchasing. This guide includes both natural gas and propane options to suit different residential setups.
-
Verify Installation Location
All listed Forimo models are designed for indoor installation. You cannot place these units outdoors or in unshielded areas. The Forimo 15-Inch RV Propane Tankless Water Heater is an exception, built for mobile RV and camper use. For standard homes, ensure you have adequate indoor space and ventilation. The compact dimensions of units like the 13.8-inch width models fit well in utility rooms. Confirm your installation site meets indoor safety requirements before proceeding.
-
Check Flow Rate Needs
Flow rate determines how many fixtures can run simultaneously. Higher GPM values support more concurrent use. The Forimo 4.74 GPM Indoor Natural Gas Water Heater supports up to three fixtures. If you need less capacity, the Forimo 15-Inch RV model offers 3.9 GPM. The Forimo 16L 4.21 GPM Indoor Propane Heater is suitable for smaller households. Match the GPM rating to your household size and typical hot water usage patterns to avoid pressure drops.
-
Assess Power Requirements
Most indoor units require standard electrical connections for digital displays and controls. However, the Forimo 15-Inch RV Propane Tankless Water Heater operates on 12V DC power. This makes it ideal for off-grid RV setups where standard household electricity is unavailable. For home installations, ensure you have the necessary power source. The RV model’s low voltage requirement distinguishes it from the residential natural gas and propane heaters in this guide.
-
Consider Venting and Hardware
Proper venting is critical for indoor gas heaters. Some models, like the Forimo 4.21 GPM Natural Gas Tankless Water Heater, include horizontal vent pipes. Others, such as the Forimo 16L Indoor Propane Tankless Water Heater, come with included venting hardware. Always check the product attributes for included components. Proper venting ensures safe exhaust removal. Verify that the included hardware matches your home’s venting configuration to ensure safe and efficient operation.
Frequently asked questions
What is the highest flow rate available in the Forimo lineup?
The highest flow rate is 4.74 GPM. You will find this capacity in the Forimo 4.74 GPM Indoor Natural Gas Water Heater, the Forimo 4.74 GPM Natural Gas Tankless Water Heater, and the Forimo 18L Indoor Propane Tankless Heater. This rate supports running multiple fixtures simultaneously in larger households.
Are all Forimo tankless heaters designed for indoor installation?
Yes, all listed indoor models are designed for indoor use. The lineup includes natural gas and propane units for homes, plus one specific RV model. The Forimo 15-Inch RV Propane Tankless Water Heater is built for mobile setups, while the others are intended for fixed indoor residential or cabin installations.
Which Forimo model is best for RVs and campers?
The Forimo 15-Inch RV Propane Tankless Water Heater is the best choice for mobile setups. It uses 12V DC power and liquid propane. With a 3.9 GPM flow rate and low 3.6 PSI activation threshold, it fits compact spaces and provides hot water for travel trailers and campers.
Do Forimo tankless water heaters include venting hardware?
Most models include necessary venting components for installation. The Forimo 4.21 GPM Natural Gas Tankless Water Heater comes with an included horizontal vent pipe. The Forimo 4.74 GPM 18L Indoor Natural Gas Tankless Heater also includes a horizontal exhaust pipe. These parts simplify the setup process for indoor natural gas units.
What is the minimum gas pressure required for operation?
Minimum pressure requirements vary by model. The Forimo 4.74 GPM Indoor Natural Gas Water Heater requires a minimum of 29 PSI. In contrast, several propane models, including the Forimo 16L 4.21 GPM Indoor Propane Heater, activate at a low threshold of 3.6 PSI. Check your specific unit’s specs.
How large are the Forimo tankless water heaters?
Sizes range from compact 15-inch cubes to taller rectangular units. The RV model measures 15 x 15 x 15 inches. Indoor home units typically measure around 13.8 to 14.4 inches in width and 21.7 to 25.4 inches in height. The Forimo 4.21 GPM Natural Gas model is notably wider at 25.4 inches.
Can I adjust the water temperature on these units?
Yes, all listed models feature digital displays for control. The Forimo 4.21 GPM Natural Gas Tankless Water Heater allows flexible adjustments between 86°F and 167°F. Other models with digital displays let you set precise temperatures. This feature ensures you get the exact water heat level you need for different tasks.
Which Forimo heater has the highest BTU output?
The Forimo 4.74 GPM Indoor Natural Gas Water Heater has the highest output at 123,000 BTU/hr. Other models offer 81,888 BTU or 68,000 BTU. Higher BTU ratings generally support greater flow rates and faster heating. Select the unit that matches your household’s simultaneous hot water demands.