I tested a robot vacuum with a unique water recycling system - here's my verdict after a month

2 weeks ago 2

ZDNET's key takeaways

The 3i S10 Ultra robot vacuum and mop is on sale at Amazon for $1,299.
This device features a unique innovation: a trademarked WaterRecycle station that distills wastewater and dehumidifies your home so you never have to refill the clean water tank.
The full device is one-of-a-kind, so its settings and setup take some getting used to, and it can sometimes take a long time to finish a task while the water distills.

As someone who reviews robot vacuums, I honestly thought I'd seen it all, especially after the launch of the Roborock Saros Z70 with a mechanical arm. But the 3i S10 Ultra came along to keep me humble.

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This isn't even a brand-new robot vacuum and mop -- it was launched six months ago in November 2024, but I hadn't heard of it until recently. And when I learned of its WaterRecycle system for the mopping feature, I knew I had to test it. Yet when the robot arrived, I was even more surprised at how different an experience it offered.

I've come to know robot vacuums inside and out. I'm a fan of these smart devices and have seen them evolve greatly over the years. I set up at least a handful of them in my house each month, so very few of them are able to stump me. The 3i S10 did just that.

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For starters, the 3i S10 Ultra is the biggest robot vacuum I've seen. Most top-tier robot vacuums delivered to my home weigh between 30 and 49 pounds, but the S10 Ultra is a hefty 80 pounds. The charging dock is like a fancy mini-fridge, and it is an appliance in its own right. 3i packs a ton of technology within the station.

When you set up the robot vacuum and charging station, you fill the clean water tank and add the detergent bottle to a separate compartment. The robot then navigates your home for a few minutes to create a virtual map of it.

The robot has 13,000Pa of suction power, so it vacuums quite well. It can also detect rugs and carpets to increase suction automatically, and it adapts its cleaning settings in real time as it goes. For mopping, the robot has a real-time self-cleaning mop roller that extends almost two inches out to clean along the edges of walls and furniture. The mop roller spins 330 times per minute and puts 12N of downward pressure for effective cleaning.

The S10 Ultra robot vacuum has great obstacle avoidance. It can avoid cords, socks, shoes, and other small items -- it only struggled with flat papers, which is common even for top performers.

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But back to the elephant in the room: the WaterRecycle system. The 3i S10 Ultra gets clean water from the very first, and probably only, time you fill the water tank. The clean water cycles from the dock into the robot's clean water tank. This water and the detergent you added during setup are sprayed by 12 outlets onto the mop roller as it cleans. A squeegee scrubs away the dirt simultaneously, which is kept in a separate dirty water tank within the robot.

When the robot returns to the dock, it empties its dirty water into a tank at the base station, and the mop roller is washed and dried. The dirty water then rises to about 194°F for distillation. The distilled water is returned to the clean water tank. There is also a silver ion module, a carbon rod, and a deodorization module to further purify and deodorize the recycled water.

The company says the waste that remains from the dirty water is scraped off, shredded, aerosolized, and collected into the base station's dust bag by a rotating cutter. This dust bag is the same one the robot uses when it automatically empties its dustbin after vacuuming.

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Furthermore, the 3i S10 Ultra also has a built-in dehumidifier that collects water from the humidity in your home's air to top off the clean water tank as needed. This automatically runs when the humidity is above 30% and the temperature is above 63°F, but it can be turned off via the 3i mobile app.

Essentially, having the 3i S10 Ultra means you'll never have to worry about emptying dirty water tanks or refilling water. All you have to do is run your vacuum as you would normally and switch the dust bag every couple of months.

I've read different reviews of the 3i S10 Ultra, and a minority have mentioned the machine giving off a smell. I have noticed a smell coming from this unit, but it's only during cleanings, so it's not permanent. I've also noticed the same smell coming from my dehumidifier when I run it, so I think it may have something to do with that. As far as the robot is concerned, I've never noticed a smell coming from it.

ZDNET's buying advice

The 3i S10 Ultra is somewhat of a niche robot vacuum and mop. Having tested multiple flagship robots, the S10 Ultra is a perfect fit for my busy family. My house has a lot of activity -- foot traffic, muddy pawprints, pet hair, messy kids -- so I really enjoy that I can always count on this robot to clean without me needing to refill its water tank or empty its dirty water.

It's truly a robot that I can set and forget. It can run on a schedule, and I've barely had to touch it after setting it up.

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But that doesn't make the 3i S10 Ultra perfect for every scenario. A robot this large is likely overkill for minimalists, apartment dwellers, and casual robot vacuum users. It's also a premium robot vacuum, so you'll be paying top dollar for it.

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