Ecovacs DEEBOT T30C

It empties into a 3 L bag and holds 4 L each of clean and dirty water, and it cleans its own base, so most homes go weeks between upkeep.

The robot is 3.9 inches tall, so it slides under most sofas and cabinets, though very low furniture may be tight.

It clears obstacles up to 20 mm, so it handles standard door sills but may stop at taller thresholds.

Yes. The dock automatically dispenses detergent when washing the mop and refills the robot from a 4 L clean tank.