The mop is where these machines differ most and where the marketing is thickest. Three mechanisms, three sets of trade-offs, and a dock that decides how often you touch it.
Disclosure — some links on this page go to Amazon, and we earn a commission if you buy through them. It costs you nothing extra and it does not change what we recommend or in what order. The full disclosure.
There are three mop mechanisms on sale. Spinning pads scrub hardest and need a dock to stay clean. Roller mops rinse themselves continuously during the run, so the far end of the floor gets the same water as the near end. Retracting arms lift the pad onto the robot entirely, which is the only design that fully solves wet carpet.
Mopping is the feature that turned robot vacuums from a convenience into a machine people actually rely on, and it is also where the marketing language is thickest. Every combo claims to mop. What they mean by it varies enormously.
The three mechanisms
Spinning pads
Two circular pads rotate under the robot, typically at around 200 RPM where the figure is published. They apply real downward pressure and scrub, which is why this is the design most flagship combos use. The weakness is obvious once you think about it: the pad picks up whatever it lifts and carries it for the rest of the room. Everything depends on the dock rinsing it, and on how often the robot goes back.
Roller mops
A single rotating roller runs the width of the robot, and a scraper plus a water feed washes it continuously as it turns. ECOVACS calls its version OZMO ROLLER and states a 175mm roller diameter. The advantage is that the water touching the floor stays comparatively clean across a whole run rather than degrading as it goes. The trade-off is a wetter floor and a mechanism with more to go wrong.
Retracting arms
iRobot's approach on the Roomba Combo j9+ is to lift the entire mop pad up onto the top of the robot when it meets carpet. There is no lift height to publish because the pad leaves the floor plane completely. It is the cleanest answer to the wet-carpet problem anyone sells, and it means the robot can vacuum and mop in a single pass without routing around rugs.
A full station does four separate jobs, and cheaper docks do fewer of them. Worth knowing which you are buying:
Empties the bin into a sealed bag. Intervals of 60 to 100 days are quoted; Dreame states 100 days on a 3.2L bag for the X50 Ultra.
Washes the pad, in cold or hot water. ECOVACS states 167F on the X8 Pro Omni; Dreame states 158F on the X40 Ultra and 149F on the L40 Ultra. Hot water matters more than it sounds — it is the difference between rinsing a pad and cleaning it.
Dries the pad, with warm air. This is the one that stops the mop smelling, and a dock without it will produce a musty pad within a week in a humid house.
Refills the robot's tank, sometimes dosing cleaning solution automatically. The on-board tanks are small — eufy states 80ml on the X10 Pro Omni against a 3L station tank — so on a large floor the refill is what lets the run finish.
What each dock does, in the maker's own words
23 of 23 models publish this figure. Every number below links to the page it came from.
Compiled from the manufacturers’ own published material on 2026-09-01. We have not measured any of these figures ourselves — see how we pick. Found an error? Tell us and we will correct it.
Which floors you can actually mop
Sealed hardwood, laminate, vinyl plank, tile and sealed stone: yes, damp. Unsealed wood, oiled or waxed finishes, unsealed stone and anything with open seams: no, regardless of what the dock can do. Carpet: never deliberately, which is the entire reason mop lift exists as a specification. The full breakdown is on which floors can you mop.
Quick picks
Ranked on the published specifications below. Tap a row to jump to the full write-up.
#
Product
Best for
Mop lift
Price
1
ECOVACSNo photo
ECOVACS DEEBOT X8 PRO OMNIA rotating roller mop that washes itself continuously while it cleans, instead of pushing one increasingly dirty pad around the house.
Roborock Qrevo CurvXThe highest published suction figure here paired with the highest published mop lift, which is the combination a mixed-floor home actually needs.
iRobot Roomba Combo j9+The mop arm retracts to the top of the robot rather than lifting a few millimeters, so it can mop and vacuum in one pass without routing around rugs.
Mopping without avoiding the carpet
Auto-retract — the mop lifts to the top of the robot
Sonic mopping is a vibrating pad with a water tank. It will take a light film off a kitchen floor and it costs a lot less than a washing dock. What it will not do is clean the pad, so by the far end of a large floor you are moving dirt rather than lifting it. As a vacuum with an occasional mop it is fine; as a mop it is the weakest thing here.
Skip this one
Dreame L10s Ultra
The dock does the full routine — wash, dry, empty, refill — and it is often the cheapest way to get one, which is a genuine argument for it. But it is an older generation with no published mop-lift height, and on a mixed-floor home an unpublished lift is exactly the specification you needed.
Combo or two machines?
For a mostly hard-floor home, one combo is enough and the docks have got good enough that the old advice to buy separates is out of date. For a home that is mostly carpet with one tiled room, a combo means carrying a mop around a house that does not need one, and a vacuum-only robot plus a cordless hard-floor mop is often better and cheaper. The full argument is on mop combo versus separate machines.
Go deeper on mopping
If you are deciding between mechanisms, read the pad-versus-roller comparison. If you already have a combo and it smells, that has its own page.
The cause is slow drying, not a dirty floor. The fix is free; the prevention is a dock feature.
Questions people actually ask
+ Are robot vacuum mops worth it?
On hard floors, yes — a damp pass every day keeps a kitchen floor in a state that a weekly hand-mop does not. On mostly carpeted homes the mop is dead weight and the lifting mechanism is one more thing to fail. It depends almost entirely on how much hard floor you actually have.
+ Does a robot vacuum mop and vacuum at the same time?
Most do both in a single pass, with the mop trailing the brush. The exception is carpet: the robot either lifts the pad, drops it at the dock first, or avoids the carpet altogether. Only the retracting-arm design fully removes the pad from the floor while it keeps vacuuming.
+ Robot vacuum mop combo or separate machines?
Combo for a mostly hard-floor home. Separates when carpet dominates and the mop would rarely be used, or when you want a mop that can genuinely scrub rather than damp-wipe. See mop combo versus separate.
+ How often should I replace the mop pads?
Manufacturers generally suggest a few months of regular use, but the honest signal is the pad itself: when it stops coming out of the wash cycle looking clean, or the fibers have matted flat, it has stopped mopping and started spreading. Pads are cheap; a stained floor is not.
+ Why does my robot vacuum mop smell musty?
A damp pad drying slowly in an enclosed dock. The bacteria doing it are the same ones that make a forgotten dishcloth smell. Heated drying largely prevents it; without heated drying you need to take the pad out after each run. Full routine on mop smells musty.
+ Can I put cleaning solution in a robot mop?
Only the solution the manufacturer specifies, and only where the tank is designed for it. Household floor cleaner foams, and foam in a pump destroys it. Some docks dose solution automatically, which is the safest version of this.
