Typical coffee machines have two user-accessible compartments: one for water and one for coffee beans. Pouring water into the bean compartment kills most machines, the repairs cost a fortune.

Now here's an improvement (Schaerer Siena-2 if that matters)

Schaerer Siena-2

this machine is permanently connected to the water pipe (like a washing machine) and so there's no water compartment, only a bean compartment.

There's also a brief hand-crafted manual next to the machine explaining that the machine is connected to water, no water needs to be poured anywhere.

Still some people try to pour water into the bean compartment.

How can the design be further improved to prevent users from pouring water into the bean compartment?

  • 84
    Our office full of engineers came up with a solution to this: a sticky note that says "Do not add water to machine"
    – xdumaine
    Commented Feb 5, 2013 at 18:39
  • 197
    add a dummy (transparent) water container that is always full Commented Feb 5, 2013 at 20:10
  • 13
    @Kaz - I guess they're from the same planet as me ... The offices I've worked in, I've never seen a coffee machine hooked up to water.
    – LarsH
    Commented Feb 6, 2013 at 3:55
  • 9
    Line the bottom of the coffee bean container with lithium.
    – Vortico
    Commented Feb 6, 2013 at 5:32
  • 10
    label with text: $500 fine - for pouring water here - it will damage the machine
    – Kamil Szot
    Commented Feb 6, 2013 at 7:24

24 Answers 24


You need the bean container or filling mechanism to communicate in its physical presence alone, that it will not hold water. Additionally, emphazising what is expected, coffee beans, in form of an icon might help.

This is just a crude sketch to visually show what I mean by "physically" communicating that the water does not go in here. Devise the coffee bean filling latch in a way that has visible holes that will obviously let water through, but are small enough to hold coffee beans.

enter image description here

What this approach does is not only solve your communication problem, but at the same time this will eliminate the actual breaking of the machine by pouring in water, because the water will simply not run into the slot (my sketch is crude and I am no product designer nor engineer, but you get the point - make the right angles and curves and whatnot and it's simultaneously a physical impossibility to get the water in).

P.S.: If you get rich implementing this I will insist on receiving a free coffee machine even though I prefer tea!

Edit: With so many comments and @trisweb's answer, I felt compelled to refine my suggested design a bit:

enter image description here

  • Make the depot a drawer, because drawers pose an even less intuitive choice for pouring water into (@trisweb's answer)
  • Then have the drawer (or its bottom part) be perforated (@JanSchejbal's suggestion)
  • Make the drawer have an explicit coffee beans icon (@Davejarvis's suggestion)
  • Make the drawer's front transparent, so users can see the level of coffee beans
  • Ensure no water can run into the machine, by making the back of the drawer seal the machine insides off when the latch is fully pulled out
  • Ensure air tight sealing of coffee beans when the drawer is closed (should be easy to implement with this design, as the perforated bottom can easily be covered when inside the machine - I imagine that engineering the bottom cover to partially slide off when inside the machine is a plausible way of retrieving the beans for grinding) (@Andrè's comment)
  • 14
    Nice idea, but coffee stays fresher when stored closed off from (free circulating air). I suspect your design may reduce the quality of the coffee due to the constant ventilation. If the machine would be right next to, say, a water boiler (for the tea you prefer), the coffee beans may absorb the water vapor produced by it and end up clogging up the grinder.
    – André
    Commented Feb 5, 2013 at 15:14
  • 30
    @André the compartment could still be sealed when shut the important part is that it does not look suitable for water when open.
    – jk.
    Commented Feb 5, 2013 at 16:47
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    @André Would modifying this idea with a slide out bean container with a solid exterior face and a perforated bottom instead work? You can have an airtight seal without adding any extra parts and the open bottom should keep anyone from accidentally filling it with water. Commented Feb 5, 2013 at 22:06
  • 8
    I'd just like to remind everyone that if you create better and better idiot-proof mechanisms... the Universe will just create a bigger idiot. :P
    – MBender
    Commented Feb 6, 2013 at 11:16
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    The best design is collaborative! Great job pulling together lots of ideas into one quite elegant final result.
    – xxx
    Commented Feb 6, 2013 at 14:41

As you observe, connecting the machine to a water pipe removes the need to add water, but the need to add coffee leaves the user with one place to put water. So what we're looking for is a way to remove the need to add coffee; the user will then have nowhere to put the water.

The solution: Mains piped coffee beans.

  • 77
    +1 - However, would humbly suggest leaving the users no space for mistake and hiding the coffee machine from them entirely. Am going to put the steaming coffee pipe right into my office... Commented Feb 5, 2013 at 22:37
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    Part of me wants to downvote because it is "Not a real answer", but the other part likes the idea of piped coffee beans so much that I just can't. Commented Feb 6, 2013 at 10:47
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    Soon we'll be saying "You mean they lived in an age without running coffee beans? Inconceivable!"
    – xxx
    Commented Feb 6, 2013 at 14:42
  • 38
    If you're going to have a pipe for coffee, why not pipe it in liquid form. Then this could actually be feasible if you ignore all the reasons it's not feasible.
    – Random832
    Commented Feb 6, 2013 at 19:13
  • 2
    One step towards living in the Diamond Age.
    – Phil
    Commented Apr 19, 2013 at 16:55

Make the user open a drawer to place the beans inside. Once closed, the drawer simply opens into the bean container normally.

Water almost never goes into a drawer.

  • 21
    Especially not into a perforated drawer. Commented Feb 5, 2013 at 23:03
  • 16
    My espresso machine has a drawer for water. It may be a poor design, but it does exist. Commented Feb 7, 2013 at 12:27
  • Use a Drawer with mini holes on the bottom, before user manages to close it, his foot will be wet - he'll probably notice something is wrong then ;)
    – j_kubik
    Commented Jul 17, 2014 at 15:39

How about only one opening which leads the water into the water compartment and beans into the bean compartment?

enter image description here

The mesh would let the water flow through and the beans pour to the side.

  • 20
    Love the idea, but when pouring a lot of water, you would likely get some into the beans, and get them wet. Moisture isn't good for coffee beans.
    – JohnGB
    Commented Feb 5, 2013 at 16:10
  • 59
    Furthermore, this might reinforce the behavior. Commented Feb 5, 2013 at 18:04
  • 39
    You need a pipe from the water compartment around to the front of the machine so the water flows straight out onto the person pouring the water in. They'll soon get the idea.
    – zuallauz
    Commented Feb 5, 2013 at 22:34
  • 4
    You need a spill reservoir in a coffee machine anyway. Look at the picture in the question; the metal plate on which the cup stands is the top of that reservoir. Paul's objection doesn't make sense. If it's no longer a problem, then do reinforce the behavior.
    – MSalters
    Commented Feb 5, 2013 at 23:36
  • 3
    When the user pours water in, it could be routed toward his/her general just below the waist area. Only a few times would this happen before the other users in the office would figure it out.
    – D. Patrick
    Commented Feb 6, 2013 at 5:07

One would imediately ask the question Are Users Stupid? which often isn't the case. The coffee container above the machine could very well be a place to pour water. Why? It's on top of the machine and since gravity still is around water would go into the machine if we used it that way. Second, it's transparent. Nespresso coffee machines use transparent water tank - so there's a chance of confusion here.

enter image description here

So how do we store coffee beans in the cupboard? Not in a transparent container, but more often in a tin jar, or in an aluminium jar. Why don't we mimic that instead? Also we could label it with big red text saying NO Water and to further emphasize our meaning place images of coffee beans on the jar to help our users.

Finally, we could place our coffee bean jar at the bottom of the machine, with tiny holes in the bottom of the jar making the water that is accidentally poured in the jar escape the machine. We'll end up with a little water on the table, but the machine still works if the user makes an error.

enter image description here

Conclusion: There are no bulletproof systems that never fail. But we can help users along the way and minimize the posability of damage through visual cues, text, placement and looks. More importantly, make sure the system doesn't get damaged when something unexpected happens.

  • 8
    Interestingly, thats an indian coffee maker. You put beans on the top container (on the right) put hot water in, put the plunger, and thick coffee comes out the bottom. The device itself solves the problem in question, by making it part of the process ;p Commented Feb 5, 2013 at 23:52
  • A transparent tank might work if it's in a form that's really awkward to load up with a liquid. Here's a design: i.imgur.com/gfWd5dJ.png that uses a cylinder with a lengthwise hole in it, which is mounted upright and then rotated sideways to feed a hopper. It's only slightly awkward to load up with coffee, because coffee doesn't have the swash that water does. Commented Feb 6, 2013 at 14:44
  • 2
    13 years later and that Nielsen article is still one of my favorites.
    – Jason C
    Commented Jul 16, 2014 at 23:59

First, don't have an open hopper (even with a lid) on top of the machine into which anything can be poured.

Second, have the beans go into a container that must be removed from the device in order to fill it. The container could be lifted off the top, or slid out from the side. It could even be like a drawer that does not fully detach.

Third, the container should have holes in it that are large enough that it could not possibly hold water, but small enough not to let the beans pass through.

Fourth, to address the issue of air circulation affecting the freshness of the beans: when the bean container is attached/inserted back into the machine, the water pass-through holes should end up sealed simply by their positioning relative to the part of the machine where the container is attached/inserted.


It seems to me that the biggest problem is that users pour water in the bean hopper because they can't think of where else to pour it and get confused. So, why don't you put two, identical plastic or aluminum cylinders on the top of the machine. Then, emblazon one with a large brown bean, and one with a large blue drop of water. This sends the message that "water goes here, beans go here, not the other way around", and, because they're right next to each other and are clearly labeled, there's no confusion. Also, because they are right on top of the machine, the hoppers and the symbology printed on them become a prominent part of the design, and users are less likely to confuse the two due to inexperience with the machine. Heck, they'll know where to put beans and water after looking at the picture on the box.

Personally the biggest problem I have with coffee machines is you have to go hunting for one or the other - the location of, say, the water reservoir is quite obvious but the location of the bean hopper is not, or the other way around. Why not make both of them quite obvious and well marked?

  • 7
    If the coffee machine doesn't need water, still do this, but still put up the sign explaining that no water is to be poured into any receptable of the machine. Then implement some automatic negative reinforcement mechanism for those who just won't read. The "pour the water back on them" mentioned above sounds good, but I have heard that electrical shocks work great on more intelligent mammals (lab mice), so maybe they would also work on dumb users who refuse to read signs. Commented Feb 5, 2013 at 23:02
  • 4
    @JanSchejbal Pouring water back on the person (or electric shocks) constitutes positive punishment (positive: adding something; punishment: to reduce the frequency of a behavior), not negative reinforcement (negative: removing something; reinforcement: to increase the frequency of a behavior). Negative reinforcement means you remove something (unpleasant) in response to a desired behavior, in order to increase the frequency of the desired behavior. Now, if the machine continually gave electric shocks until water and beans each were poured into the proper receptable, that would be neg reinf.
    – user
    Commented Feb 6, 2013 at 10:28
  • I think @ratchetfreak's idea of a dummy water container (whether sealed, filled with lucite, or simply open but not leading anywhere into the machine) is probably the best way to show users that you don't need to put water in because there already is water. Maybe even have it so there is a normal water container that the pipe runs into, and the same machine can be used with or without a plumbing hookup.
    – Random832
    Commented Feb 6, 2013 at 19:05

enter image description here

One idea is to use an upside down cartridge with a one-way valve. To refill the coffee beans, the user would remove the cartridge, unscrew the valve cap, and fill the beans into the cartridge. The one-way valve should have obvious holes so that it can hold coffee beans, but will not hold water or pre-ground beans. If the user, through some silly error, pours water into the cartridge, the valve would leak the water when they flip the cartridge upside down, hinting them that they're doing something wrong. The machine would have some simple mechanism to open the one-way valve to dispense the beans.

Additional hints could be added by using a coffee-colored plastic for cartridge, decorating the cartridge with image of beans, and some written text would also help remind them what the cartridge is for.

Water could go in the through a water pipe.

  • 14
    too much work to refill beans IMO Commented Feb 6, 2013 at 9:01
  • 1
    A coffee machine at a previous office worked similar. Only it was even simpler. The one way valve was just a simple plastic slider that would the user would manually operate. You'd close it after filling, and re-open it after putting the container back on top of the machine so the beans would fall down.
    – André
    Commented Feb 6, 2013 at 15:06

Could it be an option to make the water connection plainly visible? At the moment, it seems to be hidden behind the machine. That looks nice and clean of course, but what if you would make it very, very obvious that there is already water connected to the machine by moving the connection to the mains to a visible place, and perhaps by showing a transparent pipe running through the machine that is filled with the water to which it is connected?

  • 6
    To expand this idea, help users understand how the machine works by adding visibility for the entire process: transparent internal water tank (i.e. what's filled from the mains & heated) visible up top, beans on the other side clearly emptying into the grinder & then brew chamber. Commented Feb 6, 2013 at 14:01

Don't do anything, let it break and leave it a few weeks before fixing it. During this time, when ever anybody asks why it's not working, just explain that some idiot has broken the machine, by "adding water where the beans go, don't they know it is plumbed in and gets water by itself." Word will soon get around, and everyone will tell new employee's how to fill it.

  • 14
    The need to educate users means something is not right with the UI. If a coffee machine breaks every time it encounters an uninitiated user group, it is not going to be a popular coffee machine. And rightfully so, I might add. Commented Feb 6, 2013 at 10:44

Never allow the two compartments to be empty.

If there are always some beans, and some water in the two sections, then it’s less likely that a mistake would be made. This has obvious downsides: you’d be pretty frustrated that your coffee machine would refuse to use the last of your bean, but I imagine there’s a range where it’d be OK.

  • 2
    Maybe is simplest to place an image with beans there so even if its empty, is looks like there is the place for the beans
    – Aristos
    Commented Feb 6, 2013 at 8:57
  • 2
    Some users/customers would complain that requiring the machine to hold beans and water at all times would reduce the freshness of the ingredients. Commented Feb 7, 2013 at 12:30

There are lots of suggestion for a fake container with water, but that seems to be impractical given that this machine only has one native receptacle. It's bound to look fake.

You could take the existing plastic reservoir to a plastics store (e.g. TAP), and see if they can glue in a transparent sheet to hold a small amount of beans at the front face. The main intent is to make the coffee compartment appear full even if it's nearly empty, making it unlikely that someone will pour water directly in it.

Here's a (very) rough sketch of what it would look like:

Reservoir Sketch

  • 13
    "What the... the bean compartment is nearly full, why won't it give me a cup of friggin' coffee?!?"
    – user
    Commented Feb 6, 2013 at 10:34
  • Well the question is if you're designing a new machine, or attempting to alter the existing machine. Designing a new machine can easily mean have a real-looking reservoir, or even an actually real one that fills from the water hookup (maybe it could even be filled by hand if the same machine is moved somewhere that it can't be hooked up to a water pipe)
    – Random832
    Commented Feb 6, 2013 at 19:09
  • I like the idea of the beans beeing visible all the time, altough I wouldn't "fake" the bean level. Better make the whole container visible, so even the last few beans can be seen.
    – J_rgen
    Commented Feb 7, 2013 at 8:40

I have another idea. Instead of using a container, drawer or hopper to hold the coffee beans, how about using non-refillable containers of beans instead? Your company could sell the containers as a continuous source of revenue even after the machine has been sold. The coffee refills can be shaped and inserted in a way that obviously isn't suitable for water, like sliding them in from the side, perhaps positioned in such a way that the label is always visible so you can even see what kind of coffee is in there.


I guess this is quite close to what Philips Senseo Sarista is doing: enter image description here

Using containers that look like the picture below. Note how the container does not allow re-filling (at least not from the top), so pouring in water seems very illogical.

enter image description here

  • 10
    Sounds like the Nescafé Dolce Gusto concept - good idea indeed, from a business point of view. Personally, I'd never purchase a coffee machine that binds you to a coffee producer.
    – kontur
    Commented Feb 6, 2013 at 10:05
  • @kontur: well, yes and no. Yes as in selling the loose units, but that one actually uses a separate insert per cup of coffee. I guess Senseo Sarista is closer to what I had in mind, so I added that to the answer. Thanks for the suggestion though!
    – André
    Commented Feb 6, 2013 at 10:13
  • 1
    Ah yea, right. Did not know about that one, but that is indeed even closer. Related to that could be a disposable capsule like the one Senseo Sarista has and allow users to refill them with their own choice of coffee, also.
    – kontur
    Commented Feb 6, 2013 at 10:26
  • This idea was suggested by d33pika earlier today - albeit in a brief one-liner without much detail.
    – JonW
    Commented Feb 6, 2013 at 10:40
  • 1
    I like the idea of making a container that can not logically be meant for water, but doesn't lend to the beans deteriorating in quality due to open air. Give the user a lever or something to close it off after refilling with beans for ease of inversion and placement back into the machine. Don't like vendor lock in. Up voted, since the mechanics described here are a very practical way to solve the problem.
    – Tim Post
    Commented Feb 6, 2013 at 14:27

Instead of a compartment that takes beans, just use a regular filter basket taking coffee grounds. Have a separate grinder next to the machine, if necessary. It would take a real moron to pour water into a standalone grinder or into a filter basket.

Bunn already makes machines exactly like this, that connect to the water line. If you don't need the fancy bean grinder built-in, it should solve your problem.


A cheap IR sensor would work. If the sensor signals something present, open the flap and let the coffee beans drop into the container below for processing. If not, either there are no beans or there is water. In any case, the area where the beans should be placed would be removable so the user could pour out the water if a mistake was made, thus avoiding ruining the machine.

Better yet - Keurig!

  • Hopeless complete idiots could still ruin the machine by pouring in water and then throwing beans in the water they just poured in. But those people are too rare to care about.
    – jobukkit
    Commented May 18, 2013 at 15:32
  • Water is "black" for IR. It's even used for "heat curtains". This kind of sensor wouldn't work. Commented Jul 18, 2014 at 13:01

My idea sounds expensive (and therefore impractical), but maybe it'll trigger an idea so I'll post it. If I place the beans so they must "travel up" to the coffee grinder/filter then there's no way water to get up there, since gravity will always make water go down.

Say a crane or conveyor belt brings the beans to the grinder, and was angled/shaped in such a way that water could not travel up the belt. This belt would always grab from the bottom, to prevent "old bean pile up"

  • 1
    It wouldn't have to be that expensive. You could have a food-grade plastic cleated conveyor belt. The belt would go from a bean pour in area at the bottom up to the bean hopper. The belt could have V shaped cleats (teeth) with a hole at the point of the V for water to fall through. Beans would catch in the cleats and be moved up the belt. Commented Feb 5, 2013 at 20:30
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    Perhaps you're right. But more moving parts may mean more trouble, causing even more repairs than needed before. I suppose the only way to find out is to build and prototype it? Commented Feb 5, 2013 at 22:13
  • 1
    Even easier solution: make the coffee bean storage a tilted cylinder, with a perforated moveable bottom. To retrieve beans, the machine moves the bottom up by ~1cm. Some beans will spill fall out on the top. Any water drains out through the bottom. Since the moving parts - except for the bottom - do not touch the beans, this should be fairly robust. To prevent beans from being caught between the bottom and the side, make the bottom slightly convex.
    – MSalters
    Commented Feb 5, 2013 at 23:28

Yet another possible solution!

A few points to my idea:

  1. Make it physically look like an industrial-level coffee maker. Use of high quality materials (instead of plastic), rivets, etc would make the coffee maker look like it doesn't belong in the user's home, therefore they'll approach the use of it differently.
  2. Have an LED water level indicator on the display. It always indicates the water is full. People don't like refilling water and the indicator will always make them feel confident they don't need to worry about it.
  3. Since there is a strong correlation with the color blue for water, have the color of the coffee bean container be brown.
  4. Don't keep large water vessels (pitchers, etc) nearby the machine if possible. Keep the extra coffee container very close to the machine and visible at all times. These are more user tips, but help nudge the user to refilling with coffee instead of water.

The first two points are key. The user needs to be very well aware that this is not a coffee machine they are used to.


Instead of iconography or text information about the proper use of the compartment, I would suggest adding graphical representation of the beans that should be inside, as much as possible.

enter image description here


Add a water sensor to the bean container and wire it up to a webcam so that pictures and video will be taken of the offending party. Make it known that if you break it you buy the next one and you will get caught and publicly shamed. Bonus points if the cost of the machine can be auto deducted in payroll.


If pure usability is the goal I see a very simple and probably very cheap solution. Give the bean hopper a coffee bean print. This simple detail would instruct users that this is where beans go and therefore water would not go there. Leaving a slit in the print would allow users to tell how empty or full the hopper is.



Don't have any opening to fill in beans or by mistake water, Get beans in sealed container, sealed with cardboard at the bottom, which the machine can penetrate. Another solution is to connect bean jar through a pipe to bigger source of beans similar to how water is sourced. The bean source is maintained by a dedicated person.


Sounds like a simple label near the hopper ("Does not require water" and "Beans only") could be used. It is a little unusual to have a device such as those connected to the water main. Why would a user go to a book to read that you don't put water in it.

I think this machine brings in a few assumptions:

  1. It produces coffee or a coffee like substance
    1. Thusly, it requires, beans, heat, and water
    2. It brings in existing experience of similar devices
  2. It is a common gadget (granted its an exaggerated coffee maker), why would you need the instruction manual.

A sticker of a large coffee bean could be placed on the back of the cylinder, visible through the front, or the picture of a large coffee bean embossed in the plastic on the front (Like the Philips Senseo bean cups) Philips Senseo Around the rim of the lid, the word 'BEANS' could be engraved in a lighter shade of grey. OR place a holster for the coffee bean scoop on the cylinder and then users will visually understand that whatever goes in must need to be scooped.

Coffee cup lid Scoop Holster


When I train my dog, I had to work with rather than against his instincts. Your project here works against people's instincts because they visualize water and pouring water as part of the coffee process.

My advice is to offer a place to pour water.

Even if it is unnecessary, it will immediately clear up the problem. In the overflow grate there is an opportunity, for example. Could you add a funnel (the natural "Pour Here" sign) somewhere where adding water would improve the design?

Additionally, I disagree with adding labels or words.

Don Norman's Design of Everyday Things discusses this at length, but I'll summarize. People are smart enough to know how to use a door, so if they pull when they needed to push, it means the design is bad. To compensate for bad design, they add a sign to explain to people how to use a door. If at all possible, avoid treating your users this way. If the design is good enough then you won't need a sign/label.

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