Viomi Alpha S9

Viomi Alpha S9 robot vacuum/mop – cleans up after itself (review)

The Viomi Alpha S9 robovac self-empties its dustbin into the docking/charge station and has a clip-on robomop/sweeper plate. A good package all around and currently on special for $599 (usually $999).

Now, the extra self-emptying functionality – taking a dump – is nice. But it raises the issue – would you rather have the best robomop and robovac and manually empty its dustbin or a typical robovac/mop and occasionally empty the docking bin (don’t worry – it uses a 3L disposable bag)? Let me tell you the answer.

Faced with the fact that the self-emptying dock adds to the price, I would rather spend more on a better mop/vacuum and forget the dock. Let me reassure you that the Viomi Alpha S9 is quite a good robovac/mop – but it is no better or worse than its lower cost siblings, the V2 Pro and V3.

The Viomi Alpha S9 ticks all the boxes for a typical robovac/mop but, to a discerning buyer, there are better robovacs and robomops – they just don’t exist in the one device yet.

Read the Guide first!

We put a lot of effort into our robovac and robomop guide because a) anyone wanting to buy one should read it first to clarify what cleaning robots can and can’t do, and b) we needed a consistent set of paradigms to test and review against.

Our opening statement is as accurate as ever, “It is fair to say that technically, none have met our expectations. Perhaps those expectations are too high.”

We have found and have no fear of contradiction that a combo robovac/mop is not as good as the best robovac and separate robomop.

The two separate ones to beat are the Gen 4 Dreame L10 Pro Gen 3 3D Dual-Lidar robovac (9.3/10) and the Hobot Legee 7 robomop  (9.1/10).

Let’s see how the Viomi stacks up. We are trying a new condensed review format to save you reading so many words.

Viomi Alpha S9 self-emptying robot

Global WebsiteHere
PC Byte storeHere
Manual (PDF check downloads)Here
PriceRRP $999 on sale at review time $549
Country of ManufactureChina
CompanyA Chinese public company. Xiaomi is its strategic partner and major shareholder, and Viomi is part of its ‘mi HOME ecosystem’. Viomi has developed an ecosystem of smart products, including water purifiers, refrigerators, range hoods, switches, speakers, fans, water dispensers, mirrors, gas and electric water heaters, water processing, dishwashers and more.
MoreYou can read more GadgetGuy Viomi news and reviews here

Strategic overview and essential checklist (from our Guide)

Item ExplanationGrade
ShapeRoundAll round robovacs have issues with edge and corner cleaningPass
Lidar2D360° single LiDAR builds a 2D map – Gen 3Pass
SensorIRA forward IR sensor helps to avoid obstaclesPass
Maps5Stores up to 5, but you must take the base station to each levelPass
Map editYesAll the usual including mop and no mop zonesPass
Mi Home AppAppGoogle Play Store or Apple App store
Well designed and meets all typical needs. Modes include vacuum, mop or both, suction (Quite, standard, medium and strong), water volume (three levels), battery level and cleaning diary, area vacuum, S and Y shaped navigation pattern, up to seven schedules
Above average
Edge Poor ability to clean edges – same as all round robovacsFail
Carpet It depends on carpet type –  use a stronger suction settingPass
Sills20mmSimilar to all mop plate round robovacsPass
Other SensorsCollision and cliffTypical forward bumper sensor and cliff detector stops it from going down stairsPass
Suction2700PaOn maxPass+
Dustbin300mlAdequate given self-empty functionSmall
Water250mlAdequate for 120m2 or more – depends on settingAverage
Battery life Claimed 220 minutes, but the reality is about 150 minutes and 150m2 on standard. Approx 60 minutes 60m2 on maximum 
Battery5200mAhSamsung quality 14.4V/3.47A/50WPass
Wi-Fi2.4GHz Pass
Size (L x W x H): 35 x 35 x 9.8 cm x 3.8kg 
Dock3L dust bagRecharge time is about 4.5 hoursPass

House prep – necessary

Despite a reasonably advanced Gen 3 LiDAR and IR sensor, it still only builds a 2D map – IR is more for real-time avoidance of smaller obstacles. So, you need to do a full house prep as outlined in our Guide. It did get tangled in overhanging wires.

Map – accurate but hard to set no-go zones

There is a conundrum here, and it is common to all combo robomops. Say you have a tiled bathroom (ensuite) off a carpeted bedroom; you need to set the no-mop zone to the carpet area. But it is not entirely accurate, and the mop pad is wet anyway as it passes over the carpet. The only solution is to place the robomop in the bathroom and close the door.

We also found it onerous to get accurate virtual walls and no-go zones – the indicators were not very precise.

Cleaning efficiency – vacuum is great on hard floors

While it has 2700Pa (that is on maximum settings), it is about 2000Pa on standard and 2500Pa on medium.

We ran it in standard mode for the first two weeks, and it cleaned 75% of the test detritus from hard floors. But its carpet cleaning was not efficient at all – only 20% leaving 80% behind. We upped the hard floor to medium for the next two weeks – and it achieved 80%. We tried medium for the short sisal carpet, and it gathered slightly more. The following week we tried strong, but it still left over 50% of the detritus.

This is a common issue with all round robovacs, and the lesson here is excellent on hard floors but not carpet, particularly short ribbed sisal type or longer pile.

Speed – standard mode is about 1m2 a minute but slows if you select Y-shape cleaning (more thorough).

The Dyson V15 ‘Lie’ Detector test

Since reviewing the Dyson V15 Detector whole of home stick vac with its laser dirt ID head, we run it over the same area once the robovac has finished. As you can see, it collected an awful lot of detritus that the robovac misses – yes, it is the same for all robovacs. The majority of this comes from the edges, sills, and carpet areas.

Mopping efficiency – maintenance only

This has a static ‘drag’ plate and three water levels. Static plates mean a wet microfibre cloth; it drags a damp mop pad over the floor. There is no downwards pressure or movement – it is just like a light wipe. And that is what you get. It will not remove milk, coffee, juice, or food stains – because there is no ‘elbow grease’ behind it.

You can set it to Y-clean, and it will clean in a slower Y-pattern, but it does not appear to do much.

You can tell if the water level is correct – too low, and it leaves dry streaks and too high, and it leaves too much moisture on the floor.

Noise (dB at 1m) – acceptable

  • Quite: 64
  • Standard: 70
  • Medium: 73
  • Strong: 76

Maintenance – easy and cheap

Standard – remove the rotary brush and remove hairs. Washable HEPA dust filter, microfibre mop pad and replaceable whisker.

AliExpress has replacement dust bags, HEPA and pre-filters for reasonable prices. You can also check eBay.


The cleaning station is large and deep (550mm with the robovac) and requires more floor space and depth. You need to find an area that won’t interfere with the thoroughfare, and that is not as easy as it sounds as it needs 1.5m clear space in front and 1.5m on each side.

GadgetGuy’s take

After we review and rate test devices, we can then read third-party reviews to see if we are at odds with any findings.

The Viomi Alpha S9 gets good ratings for a round robovac/mop – and that is what we found. Its discount price is very tempting. But it is no better than any of the plethora of Gen 2 robovac/mops (including its V2 and V3 models review here 8/10). It just offers the convenience of self-emptying.

Would I buy it?

If I had mainly hard floors. But I have seen Gen 4 3D LiDAR robovacs and how they don’t need time-consuming house prep, and the robomops with ‘muscle’ do a vastly better job. Catch 22 – two devices! But, and we issue this reminder for all robovac buyers – you need a quality stick vac to do edges, stairs, and longer carpet.

Viomi Alpha S9 robot combo vacuum/mop
The Viomi Alpha S9 robovac/mop self-empties its dustbin into the docking/charge station. A good package all around and currently on special for $599 (usually $999).
Value for money
Ease of use
As good as any 2021 Gen 3 combo robovac/mop
Self-emptying is nice but not a must have
From Panmi Australia – a good company
App is not easy to use to place no-go and no-mop zones
Uses more dock floor space