3i Vacuums

3i is a young brand. It was set up in 2022 by the PICEA Group, which has development centers in Shenzhen, Tokyo and Silicon Valley and says it built over four million robot vacuums in 2024. The S10 Ultra ($700) is the one model listed here, and it is built around a single idea: a dock that never needs its water tanks filled or emptied by hand.

The dock heats dirty mop water to separate it from the waste, reusing over 60 percent of it, and tops up the clean tank by pulling moisture from room air. What is left goes into the dust bag, so there is no wastewater tank to empty and no plumbing hookup. The robot uses an extendable roller mop that spins at 330 rpm, which owners say beats spinning pads on wet spills. In one test the dock took just under five days to fill its clean tank from empty at about 40 percent humidity, so drier homes will refill from the air more slowly.

Owners are split. The ones who like it call it the most hands-off robot they have run, and say it swallows large debris such as mulch without clogging. The ones who do not describe a musty smell from the water system that some cannot get rid of, poor results on dried-on stains and deep carpet, and a dock heavy and large enough that you have to plan the room around it, with a compressor hum between runs. Measure the space for the dock and think about where its noise will carry before buying.