Do you really never have to deal with water?

In humid climates, essentially yes — the dock distills dirty mop water back to clean and the dehumidifier keeps the tank topped off from room air, so owners report going weeks or months hands-off. The catch: the dehumidifier needs roughly 30%+ humidity and reasonable temperatures to work. In dry climates or winter you're back to refilling the tank manually.

Is the musty smell complaint real?

Real but not universal — it's the single most repeated con in owner threads. Because the system recycles water and condenses moisture from the air, some units develop a mildewy odor over time. Even the reviewer who recommends it most heavily flags this: "some people complain of a mildewy smell coming from it." Other owners report no smell at all. Keeping up with the maintenance cycles seems to matter.

How big is the dock, actually?

Very. Shipping weight is 80+ lbs and owners describe it as huge — "looks like an exhibit at a kids science museum" is the quote that stuck. The distillation and dehumidifier hardware has to live somewhere. You need dedicated floor space, and since the compressor is audible, not next to a bed or desk.

Is it good on carpet?

Not its strength. The 13,000 Pa suction handles surface debris and it aced pet-hair tangle testing, but it scored below average on embedded sand in deep carpet at Vacuum Wars. This is fundamentally a floor-washing robot that also vacuums — mostly-carpet homes should buy a suction-first machine instead.

3i S10 Ultra vs Narwal Flow?

The Narwal mops dirty floors better — its track mop and hot-water washing are the class benchmark. But a tester who ran both picked the S10 overall: "it was good at everything, and hands off," because the Narwal needs constant water refills while the S10 makes its own. Flow for mopping quality, S10 for autonomy.

Never the $1,899 MSRP. It has repeatedly sold between $699 and $1,139 — Prime Day 2025 had it at $1,139 and it's hit $699 in other sales. Under $800 the value case is strong for the right home; near full price, established competitors with better stain removal and support networks make more sense.

Robot Vacuum & Mop

~$700

3i S10 Ultra

The world's first water-recycling robot vacuum: its dock distills dirty mop water and even pulls moisture from the air, so you never refill a clean tank or drain a dirty one.

Approx. price

~$700

Suction

13000 Pa

Navigation

LiDAR + Camera

Best For

Hands-off owners who never want to touch a water tank again

Check price on Amazon →

We may earn a commission. Price and availability on Amazon’s site may differ.

Specifications

LiDAR + Camera

13000 Pa

180 min

Yes

Auto Mop Washing

Yes

Obstacle Avoidance

Yes

Carpet Detection

Yes

Auto Mop Lifting

Yes

Multi-Floor Mapping

Yes

Type

Robot Vacuum & Mop

Noise Level

66 dB

Dustbin Capacity

400 ml

Water Tank

200 ml

App Control

Yes

Dimensions

13.8 x 13.8 x 4.1 in

Weight

9.9 lbs

Warranty

1 year

Model

S10 Ultra

Highlights

Water-Recycling DockNever Refill TanksExtendable Roller Mop

Pros

✓WaterRecycle dock distills wastewater and dehumidifies room air, eliminating tank refills entirely
✓Perfect score in the 7-inch pet-hair tangle test
✓Raw suction ranked among the highest of all robots in independent evaluations
✓Excellent battery efficiency - covered 1,784 sq ft on a single charge in testing
✓330rpm roller mop extends at walls and presses down with constant 7N force for real scrubbing

Cons

✗Struggled with dried-on stains, scoring 57 versus a 100-point test average
✗Deep carpet cleaning underperforms what the suction spec suggests
✗Massive dock ships at over 80 pounds and dominates its corner
✗Dehumidifier compressor adds a fridge-like hum between cleaning runs
✗Mop roller is washed without hot water, unlike similarly priced rivals

Owner Insights

The S10 Ultra is the world's first water-recycling robot vacuum — the dock distills its own dirty mop water and pulls humidity out of the air to refill the clean tank, so there's no plumbing hookup and, in the right climate, no water chores at all. That's not a gimmick; owners confirm it works, and a widely-followed tester who runs fleets of robots keeps naming it the most autonomous machine they've used. But 3i is a newcomer brand and sentiment is genuinely polarized — owner discussions aggregation puts it at just 57% positive, which is love-it-or-fight-it territory.

The practical experience depends on which unit and climate you get. The good version: it inhales large debris that clogs other robots, aces pet-hair tangle tests, mops wet messes better than spinning-pad rivals, and you truly never think about water. The bad version: a musty, mildewy smell from the recycling system that some owners cannot shake, threshold hang-ups, cleaning jobs abandoned with the robot idling off its dock, and mediocre results on dried-on stains and deep carpet. The dock itself is a commitment — 70-80 lbs and large enough that you plan a room around it, with an audible compressor you won't want near a bedroom or desk.

Price is the other trap: the $1,899 MSRP is fiction. It has sold for $699-$1,139 across Prime Day and regular sales, and at the low end of that range it's a compelling buy for hard-floor homes in humid climates that want true zero-maintenance mopping. One tester who ran it against the Narwal Flow — the reigning mopping champ — still picked the S10: "it was good at everything, and hands off." Skip it if you're carpet-heavy, live somewhere dry, or have nowhere to hide a science-museum exhibit.

Pros

+The water recycling actually works — the dock distills dirty mop water back into clean water and a built-in dehumidifier tops off the tank from room air, so owners go weeks or months without touching water
+Repeatedly called the most hands-off robot by owners who've run a dozen models — "the most hands off robot I've used is the 3i S10 Ultra"
+Swallows big debris without clogging — one owner: "giant pieces of mulch. No problem."
+Roller mop beats spinning-pad rivals on wet spills, and it posted a perfect score in Vacuum Wars' 7-inch pet hair tangle test
+13,000 Pa suction with above-average navigation efficiency (19.6 m²/minute in testing)

Cons

−The dock is absurd — roughly 70-80 lbs and enormous; one owner said it "looks like an exhibit at a kids science museum"
−Musty/mildew smell from the water system is the recurring complaint — some owners never get it, others can't get rid of it
−Weak on dried-on stains — scored 57 vs a 100-point category average at Vacuum Wars, a real problem for a floor-washing specialist
−Below-average deep carpet cleaning in embedded sand tests
−Navigation and resume quirks — owners report it hanging on thresholds and finding it "just off the base station, sitting idle" instead of finishing jobs
−The dehumidifier/compressor is audible, and below ~30% humidity the self-refilling trick stops working and you're back to manual fills