Product images: Amazon listings

forimo 18L Natural Gas, 4.74 GPM Review

Name: forimo 18L Natural Gas, 4.74 GPM
Brand: forimo
SKU: B0FP2PMFMJ

6.7Good · out of 10Rated from the listing's specs, no buyer reviews yet

Written from the listing and 19 buyer reviews, not from our own use · How we rate

The forimo 18L Natural Gas (4.74 GPM) keeps it simple: an indoor gas tankless heater with a 4.74 GPM maximum flow. It suits one shower at a time and not much more, at 6.7/10 on our rating.

Price$219.99Price on Sep 30, 2026 · may have changed

Check the price on Amazon ↗Affiliate link · price and stock on Amazon

Compare side by side ↗

Specifications

Brand	forimo
Category	Gas tankless water heaters
Stated mounting location	Indoor
Stated maximum flow	4.74 GPM
Stated gas input	81,888 BTU/h
Buyer reviews	19 · 4.2/5
ASIN	B0FP2PMFMJ

Full listing title: Natural Gas Tankless Water Heater, 4.74 GPM 18L Indoor,Constant propane water heater,Instant Hot Natural Gas Water Heater with Fahrenheit Digital Display,Multi-Protection

Listing evidence

Stated mounting location	Indoor Full listing title
Stated maximum flow	4.74 GPM Full listing title
Stated gas input	81,888 BTU Listing text

Updated October 2026

Exact listing, ASIN B0FP2PMFMJ

Rating from a published formula

Compared with its closest rivals

Two gas tankless heaters close to it on our rating, each with a dated price.

Compare side by side ↗

forimo 18L Natural Gas, 4.74 GPM

6.7Good · out of 10$219.99 Price on Sep 30, 2026 · may have changed

Stated: 4.74 GPM · 81,888 BTU/h
19 buyer reviews
Gas tankless water heaters

This product ↑

APUS 140,000 BTU Natural Gas Indoor

6.7Good · out of 10$559.99 Price on Sep 30, 2026 · may have changed

Stated: 6.8 GPM · 140,000 BTU/h · 120 V
102 buyer reviews
Gas tankless water heaters

See the review ↗

APUS 80,000 BTU Natural Gas Indoor

6.7Good · out of 10$249.99 Price on Sep 30, 2026 · may have changed

Stated: 3.6 GPM · 80,000 BTU/h · 120 V
141 buyer reviews
Gas tankless water heaters

See the review ↗

Up to 4.74 GPM from an 81,888 BTU burner

That's the maximum flow the listing states, and headline flows are usually quoted at a mild temperature rise. With January water coming in at 42 °F and a 105 °F shower, the rise is 63 °F and the real flow is lower; the maker's flow chart has that number. Counting 2 GPM per shower, as our calculator does, that's one shower and a sink at a time, maybe two showers where the water comes in warm.

One shower at a time, or two?

One at a time: that's what 4.74 GPM is for.

Two at once: not with this one. Look at the bigger units further down this page.

Great for you if…

You want an indoor gas tankless heater for one shower at a time and not much more

Skip it if…

You want a tight temperature hold: the listing claims no ±1 °F control
Two showers often run at once in your house: 4.74 GPM is a one-shower unit
You want a long review record: only 19 buyer reviews so far

What forimo promises

The seller states, word for word, in the forimo 18L Natural Gas (4.74 GPM) listing:

Only 3.6PSI water pressure required, outputs 4.74 gallons of hot water per minute, maximum temperature raise up to 75°C.
This water heater is applied with standard 1/2" NPT water fittings and gas inlet, and comes with a 2.4" horizontal vent pipe for quick installation.

Their words and their figures, not our measurements. How steady your shower stays when someone opens the kitchen tap, and what's left of that flow in January, no listing can tell you.

forimo 18L Natural Gas, 4.74 GPM, view 3

Gas, venting and what's in the box

What the forimo 18L Natural Gas (4.74 GPM) listing names:

Up to 4.74 GPM
81,888 BTU/h input
Indoor mounting

Read the installation manual for the vent, the gas line size and the clearances before you order; it overrides anything above.

forimo 18L Natural Gas, 4.74 GPM, view 4

Price and cost per GPM of stated flow

$219.99 Price on Sep 30, 2026 · may have changed

At the price on Sep 30, 2026, each GPM of stated maximum flow works out at about $46.41 (price ÷ stated GPM, our arithmetic). That puts it in the cheaper third of the 45 indoor gas tankless heaters we have a price and a stated flow for.

The online price is the heater alone. Venting, a bigger gas line where needed and the installer's day are a separate bill, often as big as this one.

The button opens the exact listing (ASIN B0FP2PMFMJ), where today's price, stock and seller apply.

forimo 18L Natural Gas, 4.74 GPM, view 5

A better fit for your house?

Two showers and the dishwasher at once? The Ranein 190,000 BTU Natural Gas Indoor (7.9/10) states up to 8.5 GPM.

Our take

The verdict

The forimo 18L Natural Gas (4.74 GPM) is about a 4.74 GPM maximum flow, and it doesn't pretend to be more. Only 19 buyers have rated it so far (4.2/5), so treat the score as an early read. The catch with this forimo indoor gas tankless heater: no stated temperature hold, while most picks here claim ±1 °F. We'd pick it if you want an indoor gas tankless heater for one shower at a time and not much more; otherwise, put it next to the APUS 140,000 BTU Natural Gas Indoor first.

Check the price on Amazon ↗Affiliate link · price and stock on AmazonAll gas tankless water heaters →

Living with it

Install day

Old tank out, unit on the wall, vent through the wall or the roof. Plan the gas line for 81,888 BTU/h; a licensed pro handles it, and often a permit.

The first shower

Hot water arrives after the cold already in the pipes, then stays. A trickle from a bathroom tap may not light the burner; open it a bit more.

The first winter

January water comes in colder, so the same unit gives fewer GPM. Stagger the showers if you sized it tight.

Once a year

Flush the heat exchanger with a pump and a descaler (the service valves make it an hour's job), and clean the inlet filter. Our flushing and descaling guide has the checklist.

What buyers say

Buyers give it 4.2/5, a solid record, slightly below our ranked picks' 4.3 average. Only 19 reviews so far, and our formula damps averages built on fewer than 50.

The numbers

Buyer rating: 4.2/5
Reviews: 19
Ranked picks' average: 4.3/5

The one thing we'd check first

Before the forimo 18L Natural Gas (4.74 GPM) goes in your cart, check your gas line: 81,888 BTU/h is a lot of gas at once, so ask your plumber whether the existing line can feed it.

Before you buy

Your winter flow

4.74 GPM is the headline. In a northern January the water comes in near 42 °F, so a 105 °F shower needs a 63 °F rise and the real flow drops. Our flow-rate calculator runs the numbers for your house.

Vent and gas line

Ask the plumber to check the gas line size and the meter against the heater's input, and to quote the vent route at the same visit. Our install cost guide shows what that usually adds.

The warranty terms

Read what it requires: a licensed install, the gas type and regular flushing are the usual conditions.

Flushing

Hard water scales the heat exchanger. Service valves on the water lines turn the yearly flush into an hour with a bucket and a pump; our flushing and descaling guide shows the routine.

How it compares

How the forimo 18L Natural Gas (4.74 GPM) stacks up against the closest alternative, the APUS 140,000 BTU Natural Gas Indoor.

Criterion	forimo 18L Natural Gas, 4.74 GPM	APUS 140,000 BTU Natural Gas Indoor
Our rating	6.7/10	6.7/10
Max flow	4.74 GPM	6.8 GPM
Gas input	81,888 BTU/h	140,000 BTU/h
Fuel	Not stated	Natural gas
Efficiency	Not stated	0.81 UEF
Buyer reviews	19 · 4.2/5	102 · 4.0/5

Both score 6.7/10. The APUS 140,000 BTU Natural Gas Indoor adds more flow (6.8 GPM) and a bigger burner (140,000 BTU/h), while the forimo 18L Natural Gas (4.74 GPM) brings a higher buyer rating (4.2/5).

Compare side by side ↗See the APUS 140,000 BTU Natural Gas Indoor review →

The score in detail

How we rated it

Spec-based rating on a 4.5–8.5 scale: 4.5 + average of the 4 criteria × 0.4. Capped at 8.5 because no customer evidence is included.

Key specifications

7 / 10

Build, warranty & certifications

4 / 10

Listing documentation

6 / 10

Fit & compatibility

5 / 10

This product has no captured buyer-review record yet, so its rating comes from the documented listing alone: four criteria scored out of 10 (key specifications; build, warranty and certifications; listing documentation; fit and compatibility), placed on a 4.5–8.5 scale. Read the full methodology.

Read the methodology →

Frequently asked questions

Is the forimo 18L Natural Gas (4.74 GPM) any good?

We rate it 6.7/10 (good). The rating comes from its documented listing alone, as no customer-review record is captured yet.

How much hot water can the forimo 18L Natural Gas, 4.74 GPM deliver?

The listing states a maximum flow of 4.74 GPM and a gas input of 81,888 BTU/h. The headline flow is a mild-weather number: with cold winter water coming in, the same unit gives you less. Read the maker's flow chart at your winter rise, or let our flow-rate calculator do the sums.

Can the forimo 18L Natural Gas, 4.74 GPM be installed indoors?

Yes, the listing says indoor mounting. That means a vent route to the outside, combustion air and a gas line sized for the unit, all as the maker and your local code require. A licensed plumber or gas fitter sorts that out.

What do you get with the forimo 18L Natural Gas (4.74 GPM)?

Its listing states up to 4.74 GPM. These are the seller's figures, not our measurements: how steady the temperature is in your shower and how it copes with your winter water can't be read from a listing.

What should I check before ordering the forimo 18L Natural Gas (4.74 GPM)?

Your winter flow: 4.74 GPM is the headline. In a northern January the water comes in near 42 °F, so a 105 °F shower needs a 63 °F rise and the real flow drops. Our flow-rate calculator runs the numbers for your house. Vent and gas line: ask the plumber to check the gas line size and the meter against the heater's input, and to quote the vent route at the same visit. Our install cost guide shows what that usually adds. The warranty terms: read what it requires: a licensed install, the gas type and regular flushing are the usual conditions. Flushing: hard water scales the heat exchanger. Service valves on the water lines turn the yearly flush into an hour with a bucket and a pump; our flushing and descaling guide shows the routine.

Where can I buy the forimo 18L Natural Gas (4.74 GPM)?

We link to the exact listing on Amazon, where today's price, stock and seller apply. It is an affiliate link, and it has no effect on the rating.

Have you used the forimo 18L Natural Gas (4.74 GPM) yourselves?

No, we haven't used it ourselves. Everything on this page comes from its listing and 19 buyer reviews, read line by line and weighed with our published formula.

Gas tankless water heaters ↗Comparison tool All product reviews