Right off the bat, we feel compelled to explain why this technology is so revolutionary: the iRobot Scooba 390 isn't like any other robot vacuum that comes attached with a "mop" cloth accessory.

Instead, the iRobot Scooba actually has a jet that shoots out clean water, a brush that scrubs the floor, and a vacuum to retrieve the dirty water (into a separate tank). This literally scrubs, vacuums and mops your floor. This also means you can (more or less) replace mopping and scrubbing the floor with this robot.

Other robot "mops" simply use a cloth to push the dirt around your floor. The iRobot Scooba 390 replaces your manual scrubbing and mopping.

With this handy explanation, we'll go further into our review of the iRobot Scooba 390 (which isn't perfect).

Specifications

• Dimensions: 37cm (diameter) x 9.2cm (height)
• Weight: 4kg
• Cleaning type: wet (4-stage: pre-vacuum, wash, scrub, vacuum)
• Navigation: random (doesn't map floor)
• Accessories: virtual wall, battery, cleaning solution sample, suction bulb
• Battery: 4,100 mAh (NiMH)
• Special features: wall-following, cliff detection

How the Scooba 390 works

The iRobot Scooba 390 has 2 water tanks - 1 for clean water (that can be mixed with cleaning solution) and 1 for the dirty water that it collects.

The iRobot Scooba 390's manual (and marketing materials) state that the robot uses a 4-stage cleaning system. This is accurate, but it doesn't actually operate in 4 separate stages. The 4 stages all happen at one time.

In other words, the Scooba does all four of the following at the same time:

1. First, it vacuums loose pieces of dirt (and any other remnant dirty water already on the ground).
2. It then sprays a thin film of water (which would include any cleaning solution you might have included in its clean water tanks).
3. Using a brush, the Scooba then gently scrubs the ground.
4. Finally, another set of vacuums suck up the dirty water on the ground.

The navigation

The iRobot Scooba 390 doesn't have the navigation chops of its smarter 900-series Roomba cousins or the competing Neato robot vacuums.

Rather, the Scooba navigates by moving around the ground with a fixed algorithm, aided by a front touch bumper and cliff detection sensors.

The "random" navigation of the Scooba is, for a "dumb" form of navigation that doesn't map the layout of the house, actually really smart. Our living room contains a breakfast counter that partially separates the floor space, but the Scooba never fails to reach all the separated areas when cleaning on a full cycle.

The Scooba 390 navigates by:

1. spiraling - this is the main form as cleaning as it moves in concentric circles to thoroughly clean the floor.
2. wall following - the Scooba is able to guess when it has hit a wall, then tries to follow the contours of that wall.
3. room crossing - every once in a while, the Scooba will stop its spiraling or wall following, and instead just move straight a certain distance to ensure it reaches every area of the room.

I was skeptical when I first saw the Scooba's navigation (especially next to the impressive floor mapping of our Neato Botvac), but it has performed admirably, and never failed to clean an entire room.

But because the Scooba 390 doesn't map your floor area, it has to be used to clean one room at a time. You can't set it and forget it to clean your entire house. Also, because it's unable to tell a wall from a raised carpet, you'll want to move away small rugs and other movable furniture (like chairs) in order for the Scooba to clean your floor more completely.

Thankfully, the iRobot Scooba 390 is smart enough to avoid moving onto raised carpet surfaces and getting them all wet. Provided the carpet or rug is thick enough, its front bumper will bounce off of it and Scooba will treat it like any other wall.

The Scooba also has cliff sensors, and will detect when there's a step or if it's about to fall off a ledge. It'll cleverly avoid the "cliff" and turn back.

The cleaning cycle

The iRobot Scooba 390 comes equipped with a Nickel-Metal Hydride battery with a 4,100 mAh capacity. On a full charge, the Scooba is able to complete 2 full cleaning cycles. A complete cleaning cycle takes about 45 minutes, so the Scooba is able to last up to 90 minutes of cleaning.

The Scooba 390's cleaning cycles are entirely dependent on the amount of water in its clean water tank. A cleaning cycle for the Scooba consists of using up all the water in its clean water tank (about 4.5 cups of water).

A full ceaning cycle is sufficient for cleaning a large room of up to 40 square metres (which, when furniture blocking the floor is included, is usually equivalent to about 30-35 square metres in real terms for the Scooba). During this period, the Scooba would have cleaned every area in the room multiple times.

The Scooba 390 detects the end of a cycle when its running low on water in its clean water tank. This is when it switches from 4-stage cleaning to a one stage cleaning mode - vacuuming up whatever remnants of dirty water is left on the floor. You know when it's in this mode when its play/pause button is blinking.

The virtual wall

If you have rooms in your house are more than 40 square metres, for maximum efficiency, you'll want to use the vertical wall to partition your room up so that the Scooba will clean portions of your room at a time.

The virtual wall works by shooting out IR beams that inform a receiver on the Scooba not to come near. The virtual wall emits a small halo to prevent the Scooba from bumping into it, as well as a larger beam that is effective for about 1 to 2.5 metres. The Scooba will treat that beam as it does a wall, and move away from it.

If you need to separate a space wider than 2.5 metres, you'll need more than one virtual wall to partition off the room.

Alternatively, you could also use furniture to partition up your room, although that might require a lot more effort.

How to use the Scooba 390

Like we mentioned above, the iRobot Scooba 390 needs some attention, and cleans your house one room at a time.

Preparation and cleaning the floor

Before the Scooba can start cleaning your room, you'll want to prepare it for cleaning for best performance. This means packing all loose items from the ground (like random socks or stationery), and moving small rugs and movable furniture (like chairs) to another room temporarily.

As for the Scooba itself, you'll just have to fill up its clean water tank to the right amount, insert the tank into the robot chassis, turn it on and press play. 

How much water you'll have to fill into the clean water tank depends on the size of the room:

• For a room that's about 40 square metres or less, you'd want a full tank of 4.5 cups of water (takes about 45 minutes).
• For a room that's between 25 and 40 square metres, you should use 3 to 4 cups of water (takes about 30 minutes).
• For a room that's below 25 square metres, 2 to 3 cups of water is sufficient (takes about 20 minutes).

Of course, you could always opt to use more water for a smaller-sized room if you want extra cleaning - the Scooba will simply scrub your floors for a longer period of time by covering the same area multiple times.

The clean water tank of the Scooba 390 can either be filled with pure water or soapy water. The Scooba 390 comes with a sample packet of cleaning solution that you can mix with water to fill the clean water tank. You could also use your own detergent.

It's important that the detergent is water-based, and doesn't contain any oil, wax or additional polymers (that are frequently used for giving a waxy sheen on marble floors). These substances could build up inside the Scooba's pumps and cause it to jam up and spoil.

The ratio of cleaning solution to pure water should not exceed 1:10, so on a full tank you should, at most, use half a cup of detergent.

Depending on the surface type of your floor (more details are explained below), varying amounts of the clean water will be left on your floor. You'll want to take this into account if you're using cleaning solution/detergent to clean the floor, as you might have some soapy residue left on the ground after washing.

Of course, the Scooba's final vacuuming mode helps alleviate this, but if you don't like the idea of leaving any soapy residue on the floor, you can fill the clean water tank with more pure water and set the Scooba to clean the floor again. This second round using only pure water should serve to vacuum up all remaining soapy residue.

Cleaning the Scooba

After the Scooba 390 is done cleaning your floor, you'll have to clean up the robot to preserve its lifespan.

To explain this concept of preserving the Scooba's lifespan, we'll go a little bit into its history. The Scooba line of robots actually has a long heritage - it was first launched in 2006, but by 2016 it was discontinued in favour of the Braava line of robots (which operate only as a wet mop).

One of the main reasons why iRobot discontinued their very useful Scooba line was because the Scooba robots kept breaking down despite their apparent durability. It's likely that iRobot discovered that it was difficult to educate consumers how to properly maintain their Scooba robots to preserve their lifespan - it's possible that many of these Scooba robots broke down due to a lack of maintenance and not manufacturer defects.

So, if you use a Scooba, you would want to properly maintain it and you'll find that it has a suitably long lifespan.

After your Scooba is done cleaning a room, you'll have to remove the water tank and remove all the dirty water. After that, you'll want to fill the dirty tank with clean water, seal it, then shake the tank vigourously then expel the water. I usually repeat this 3 times.

You don't have to clean anything else if you're going to use the Scooba to clean more rooms. Only once your entire house is cleaned, and you're ready to recharge and keep the Scooba, will you have to follow the next cleaning steps.

Once you're done cleaning the entire house, you'll have to remove the filter and vacuum port, remove or solid dirt from them and wash them.

A final, important step is to press the brush eject button and remove the brush on the bottom of the Scooba. You'll have to open up the brush and wash the entire mechanism thoroughly. After this, you'll want to dry all the parts before inserting them back into the Scooba.

Suitable house layouts and floor material

The Scooba 390 is very useful, but it isn't universal in its application.

It works most effectively on homogeneous tiles - so if you use flat ceramic, porcelain or marble tiles, you're good to go. In fact, it's able to vacuum up to 80-90% of the dirty water on the floor, so it'll be very effective in cleaning your floor.

Take note, however, that if you're using a tile that's not very hard (like marble), it might get scratched by the brush. But for ceramic or porcelain, you won't be facing any problems.

If you're using tiles that aren't homogeneous, but are bumpy or textured, the Scooba actually still works really well. But because it's harder for the squeegee and vacuum to suck back all the dirty water on the floor, you'll find that only 60-70% of the dirty water will vacuumed away. The rest will evaporate quickly.

For this reason, if your tiles aren't homogeneous, you'll have to regularly sweep the floor (or use a robot vacuum, as we do) for your floor to be extra clean. Also, you'll want to take note of this if you mix detergent or cleaning solution into your clean water, because some soapy residue will be left on your floor.

We actually use non-homogeneous tiles ourselves, and find that the Scooba 390 is still very effective. We use a robot vacuum (the Neato Botvac) to vacuum the house daily. And if we use detergent in the clean water (for the less common occasions where the floor is sticky), we'll  subsequently clean the floor again with another round of pure water. This is good enough to remove any soapy residue from the tiles.

Other floor materials that are suitable for the Scooba 390 are high-quality (and waterproof) laminate, like HERF laminate - the Scooba 390 will work as effectively on these types of flooring as on homogeneous tiles. It's essential that the laminate is waterproof, though. If your laminate flooring isn't waterproof, water might seep underneath it and cause warping.

The Scooba can work on hardwood, but only if it's waterproof. On hardwood, the Scooba will work as effectively as on textured tiles.

If you use parquet (or other glossy-type wood flooring), it's possible that the brush might scratch the floor, so take note accordingly.

The Scooba is clearly unsuitable for carpeted flooring, in which case you'll just want a good robot vacuum.

When our house was designed, we ensured that most of our furniture had at least 15cm clearance from the ground, which is more than enough for the Scooba to go under (it has a height of 9.2cm). For the Scooba to be effective, you'll want to have as little clutter and wires on the ground as possible.

It's interesting to note though that the Scooba, despite lacking the ability to map the floor layout, actually navigates well and never gets stuck in between furniture. You'll still want to move most of your chairs and small rugs temporarily into another room - this helps the Scooba clean more surface area on your floor.

If your room is bigger than 40 square metres, you'll have to partition it using pieces of furniture or using the virtual wall accessory. The Scooba 390 works most effectively when cleaning smaller rooms (so that it quickly overlaps the same area multiple times, allowing it to spray clean water and vacuum up dirty water).

Does the Scooba 390 clean effectively?

The answer is unreservedly, yes. The iRobot Scooba 390 has its share of issues, quirks and problems, but when it comes to cleaning suitable flooring, it works very well.

Since moving into our new place nearly a year ago (as of the time of writing), we have never had the need to manually mop nor sweep the floor. Sweeping functions have been handled by our Neato Botvac D85 daily, while mopping functions have been carried out by the iRobot Scooba 390 weekly.

In fact, because the Scooba actually scrubs the floor and vacuums up the dirty water, it operates more effectively than simply mopping the floor. And because we can use floor detergent when required, there's no difficulty with keeping the floor clean.

Having the Scooba do the cleaning also means we save a lot of time. Time is still spent cleaning the Scooba, but that's much faster than cleaning the floor. This also gives us flexibility in our schedule - we can set the Scooba to clean the living room, go out for dinner, then come back later to clean the Scooba.

If we ever feel like the floor needs extra cleaning, we can just use more water than necessary. For example, if our 25-square metre bedroom requires more cleaning, we can just use 4 cups of water in the clean water tank, and it gets "extra" cleaning. If our 40-square metre living room feels dirty, we can either use detergent or have the Scooba do 2 complete cycles to clean it.

You'll find the Scooba even more effective than we have if you have homogeneous floor tiles, because the Scooba will vacuum up a greater proportion of the dirty water left on the floor. So, yes, if your use case suits the Scooba, it'll be a great convenience in your life.

Problems with the Scooba 390

This isn't to say that the Scooba 390 is perfect. There's a reason why iRobot discontinued this line of robots in favour of the Braava.

First and foremost, you'll have to be willing to maintain the Scooba 390 to keep it running. This means regular cleaning of the robot itself (as described above), and replacement of parts where necessary.

Yes, you read that right, parts might need to be replaced. In my house, I've found that the stock rubber tires that come on the Scooba aren't very resilient. Over time, they've worn down and some small pieces of rubber have even fallen off. This isn't a huge problem, though. It's easy enough to find replacement tires online. I've purchased third party rubber tires from ebay that are more resilient and don't quite wear down as much.

The other rubber components (especially the brush and vacuum port) may also tear if you're not careful when taking them out for cleaning. These parts are also replaceable. It's useful to note also that the Scooba may continue to operate perfectly fine even if there's some minor tearing of these parts. In which case, you can continue to use it normally.

Perhaps the greatest issue with the Scooba is its inability to clean corners. The brush and vacuum of the Scooba 390 have a gap that's approximately 3cm away from the side border of the Scooba. This means that the very edge along your wall, as well as corners, don't get scrubbed. This is a very small area that can be cleaned manually. But if you don't clean this part of the floor yourself, over time dirt or stains might build up there.

Also, as with any other battery-operated device, you'll have to care for the battery. Even if you do, it'll still degrade over time. Whenever you store the Scooba, you'll have to charge the battery up first, then take it out for storage. If you leave it in the Scooba over a prolonged period there might be accelerated degradation. Once you find the battery's capacity to be too low (which can happen over the course of a year, or perhaps longer), you might have to find a replacement battery on ebay.

You'll also have to be patient - a complete cleaning cycle for a 40-square metre room takes 45 minutes to complete. Although you might be able to scrub or mop the floor manually more quickly than that, the advantage is that you don't have to physically be there while the Scooba is cleaning (you can just leave the Scooba there, set it to clean, then go do your own things and come back later when its done). The downside, however, is that you have to plan your schedule accordingly. 

Keep in mind also that the Scooba can only clean for 9 cups of water (about 90 minutes), after which you'll have to recharge the battery. So for our 84-square metre house, we need about 3-4 hours to clean every room, sometimes longer. Of course, this isn't so much of an issue for us because we usually do the cleaning on weekends, and we have the freedom to do whatever we want while the Scooba is cleaning.

Our floor tiles are made of ceramic, so we have no issue with scratching. But tiles made of softer materials may get scratched.

Also, because our tiles are heavily textured (they have a wood grain design), the Scooba leaves about 30-40% of the water it sprays out after cleaning. If the room is smaller, this is less of an issue because it's last stage of pure vacuuming (when the Scooba runs out of water it continues vacuuming the floor without spraying water for a while) helps to vacuum up most of the water.

At this point, the remaining water on the floor usually isn't dirty, and we're alright with letting the water droplets evaporate by themselves. This isn't an issue for us also because the floor is vacuumed daily by our Neato Botvac. But if you don't regularly sweep the floor, then the Scooba's inefficiency on a textured flooring might be a problem for you.

This leads us to our final problem, which is that the Scooba requires your floor to be reasonably clean in the first place. This doesn't mean that you actually have to pre-clean your floor for the Scooba - that's ridiculously and you obviously don't have to do that. But if you spill soup on the floor, you'd be well-advised to clean up the soup with a cloth first before setting the Scooba there. 

Hair will get tangled in the Scooba 390's brush, and if you don't clean the brush regularly it will get jammed over time. This isn't a concern for us at all because we vacuum regularly, and we clean big spills and chunks of dirt manually (with a cloth) as and when it happens. But if you don't, then the Scooba might not be as effective when cleaning your floor.

Should you get the Scooba 390?

The story for the iRobot Scooba 390 seems to be that it's great at what it does - scrubbing, vacuuming and mopping your floor - but only if it suits your use case. If you have carpeted flooring, parquet, or simply a very cluttered house, then absolutely you should not get a Scooba.

In other words, the Scooba 390 is extremely useful and effective provided that your house suits the robot. It seems counter-intuitive, but your house has to suit the robot, and not the other way round.

But if you don't enjoy spending time mopping your floor, but you have a layout and floor material that fits the Scooba's design, then you'll find the iRobot Scooba 390 to be a massive convenience in your life and maybe even a godsend.

Of course, just because you want a Scooba doesn't mean you can get your hands on one. The Scooba 390 has been discontinued for a number of years now. Most Scoobas for sale are usually either sold pre-owned or are overpriced.

If your house suits the iRobot Scooba 390, and you can find a good deal on one, then you should absolutely get one (and maintain it well).

How to buy the iRobot Scooba 390

The iRobot Scooba 390 has been discontinued for a while now, so it's difficult to buy a brand new one. You can, however, still buy it from eBay (especially used models). Alternatively, you can search for the slightly newer iRobot Scooba 450 (also available on eBay).

Do we enjoy the smart life with this? Absolutely - our house was designed to suit robot cleaners and the Scooba has obviated so much housework for us.

Who should buy this? Anyone whose house suits the Scooba, who's willing to maintain it, and who doesn't like doing housework.

Who shouldn't buy this? Anyone whose floor is carpeted or who doesn't know how to use a screwdriver.