Watercone – An Ingenious Way To Turn Salt Water Into Fresh Water


The Watercone is an ingenious device that can take salty water and turn it into fresh water using only the power of the sun. The nice thing about this device is it is bone simple, uses the sun instead of fossil fuel, and is cheap to make and easy to use.

water cone

The Watercone is surprisingly a cone, that you place over a pan of salty water (or over a marsh, or any damp ground) leave it out in the sun, water evaporates, the condensation trickles down the side of the cone, at the end of the day you flip it over, remove the cap at the top and drink the water.


This device has the potential to really do a lot of good for a lot of people. So many people live in areas where the ground water has been polluted by salt incursion due to over pumping, or in areas that simply don’t have large fresh water sources (south pacific islands, sub-Saharan Africa, south-east Asia). The Watercone is made from UV resistant plastic and they claim that it will last up to five years, after which it can be used to collect rainwater and funnel it into bottles.


They claim that on average one Watercone can produce one liter of water per-day. I could image a whole fleet of these things for a village. They float, so you could place them over a small pool of salt water and just collect fresh water all day. At about 20 Euros it would pay for itself in a couple of months and provide potable water for the next 4-5 years. It is also recyclable and non-flammable.

The Watercone website has some really interesting information and I highly recommend checking it out.

1. Much cheaper than bottled water.
Watercone life expectancy: 3 to 5 years. Price: planned below € 20.- Average Price of 1 liter of bottled water in developing countries: $US 0,50. Presuming a daily usage of the Watercone and a daily average yield of 1 liter, the Watercone has paid for itself in about 2 mounth and will work for free the next 5-7 years!

2. Absolutely, low concept and low tech.
As opposed to other types of solar stills which feature electronics, photo-voltaic cells, tubes, filters, many parts, etc. the Watercone concept is understood within seconds with absolutely no need for academic background. Additionally it (cone & pan) is made from Bayer Makrolon, a high-tech ultra-rugged and highly recyclable polycarbonate, virtually insensitive to UV exposure or breakage, an all too common result of rough transport.

3. Perfect for coastal dwellers.
There are at least 50 sunny, developing countries worldwide with a significant amount of sea- or coastline. Many from their populations, hundreds of millions, live in nearest proximity to water but cannot drink it or use it for agriculture, because it is saltwater. Large families, hamlets, villages could all experience dramatically improved quality of life starting from as little as a dozen Watercones set up close by the sea.

4. Perfect for medical purposes.
There are thousands of hospitals in developing countries, field and mobile hospitals, first aid and emergency medical units around the world that are located in sunny climates and lack condensed water. Outfitted with just a dozen Watercones, a little field hospital could harvest 15 liters of condensed water per day. More than enough to make a difference for life or death.

5. Creates jobs.
For centuries water vendors have walked the markets of hamlets, villages and cities around the world, mostly in Africa, the Mid East and Asia. Based in the vicinity of salt or brackish water and outfitted with a minor credit line, these vendors could invest in a dozen Watercones and sell 15 liters of water a day and have their investment returned in no more than half a year.

126 thoughts on “Watercone – An Ingenious Way To Turn Salt Water Into Fresh Water”

  1. You actually don’t want the water to get too hot. You need to have a temperature difference that is large enough to get the water to condense on the cone, if the cone is too hot you will not get any condensation until the sun goes down.

  2. problem being the water gotten this way has no minerals and salts whatsoever. it is like distilled water. drinking this actually sucks salts and minerals from you body, leaving you in very unhealthy condition.

  3. Hal: if you do make this DIY be sure to let me know I will highlight it

    Tim: I would say that you should worry more about not having any water at all, if the only water available to drink is ocean water, you are in big trouble. So long as people eat food with minerals and salt in it they will be fine.

  4. this was on survivor man, he used urine though, not salt water.

    He just dug a hole, pissed in it, placed a cup in the center of the hole, then covered the hole in plastic with a bit of sand to weigh down the center and allow the condensation to trickle above the cup.

  5. Just wondering if this could be scaled up. Imagine a cone the size of a football field suspended over the ocean between two pillars, and every so often it flips over on its axle and dumps out its water through a pipe to a tank on the shore.

  6. It’s unlikely this could scaled up economically. Once you start trying to build an enormous version of this watercone, you’d be sinking in millions of dollars. I would bet that you very quickly end up in a positino where it’s cheaper to build a wind/solar powered osmosis pump that produces WAY more fresh watter at similar cost and maintanance costs.

  7. It could be even easier, attach a siphon hose at the base of the cone and simply allow the force of gravity to push the desalinated water into a cistern/tank below the cone level.

  8. Rob and Dave, just think for a minute about the design of this unit: it will not be feasible to “adapt it to larger needs” or “scale it up”. For effective condensation, you need shallow water. This will always take up heaps of space. Also, the output is poor – 1 litre a day, sheesh. No wonder you want to believe it can be made to work better, but I just don’t think its the case.

    For effective use, you need heaps of these. Then someone has to collect them, using uncontaminated vessels (otherwise, what’s the point of distillation?) And they take up a whole lot of space, and can’t be disturbed (knocking them would splash distilled water out of the cone’s reservoir). Oh, and you need sunlight for it to work. 4 counts against.

    On the plus side, these things are cheap and portable. 2 non-trivial advantages.

    The thing is, plenty of higher capacity filtration systems exist. The ‘rabbit’ filter is quite common throughout SE Asia. Its by no means portable, but it can provide up to 20 Litres of clean drinking water overnight. It costs about USD20. Its the size of a large waste paper basket – not as portable as this device, but still portable. Best of all, local companies make these things in the region, not foreign businesses.

    To finish the essay, don’t just read up on this cone. Look at all the other options available. Be informed!

    oh and btw, it costs THB1 (about USD$0.03) to purchase 1 litre of filtered water from a government water station. Admittedly this is probably subsidised, but its a far cry from 50 cents.

  9. 1: How about a straw?

    2: Could I float this in an actual pool of salty water? Say I’m living on the coast, have a dozen of these floating in the water near my house, anchored so they don’t float away.

    3: If floating would work, how about a hexagonal-modular system with connecting collection-tubes? Float a raft of them.

  10. What about the interface between the cone and water it touches? If the water is bad (brackish) I would worry about that bad water running on the outside surface to the collection bottle….

  11. This may or may not work in practice. I’ve tried this design before on boats. In a salty environment with any sort of wind, you end up with salt deposits on the inside of the funnel, which takes more water to remove each day than you gain from the process. So water is less salty, but brackish due to salt residue.

    With this particular design, I have to wonder how long the plastics will last in the direct sun and remain clear, and whether there will be any carcinogens introduced into the water, which is what normally happens when you run hot water against a plastic surface.

  12. re: safety of distilled water

    I suggest you read the following article concerning the myths about distilled water. I have been drinking distilled water for almost two years now with no ill effects. It tastes better and is better for my coffee / cappuccino machine, and my macaroni. I really think you should stop perpetuating these myths and do some research first. http://www.durastill.com/myths.html

  13. This was on Voyage of the Mimi, a educational show that aired on PBS in the 80s. As a child of the 80s this was one of the few things I remember .

  14. at steve: can you provide some links to that ‘rabbit’ water system, and other water systems? Thanks a lot

  15. This is a great product. Unfortunately, the people who could really use this simple technology are the ones who will be the least able to afford it.

    In areas of the world where potable water is in short supply, there is also a shortage of cash. Think any third-world spot.

  16. Only 1 litre per day? In most hot dry places you need 2-4 times that to replace what you’re losing in sweat and urine.

    Methinks you’d need 5-6 of these to be fairly sure of your water supply.

  17. This is only good for emergency water. The collection ring will eventually become a breeding ground for bacteria unless it it regularly washed with soap and …. umm…. clean water.

  18. The principle behind this device has been around for years. I remember as a child, maybe 20 or 30 years ago, reading instructions for purifying water in a desert (eg if car breaks down): 1) Dig a hole.
    2) Put a can or something to collect water in the centre.
    3) Pour dirty water or urine into the hole (making sure it doesn’t get into the can in the centre).
    4) Cover the hole with a plastic sheet, a rain coat or other impermeable material.
    5) Hold down the edges of the sheet with rocks. Put a rock in the centre of the sheet to weigh it down.

    The sun will evaporate the dirty water. It will condense on the inside of the sheet and dribble down to the lowest point (where the rock in the centre is). It will then drip into the can in the centre of the hole.

    Also, survival life rafts for aircraft and ships have come equipped for years with solar stills for purifying salt water.

    Not to say that this isn’t a good idea, just that it’s been around a long time.

  19. You forgot one problem: Since it’s condensed water it has no minerals, so maybe you also want to extract some of that salt from the seawater to get at least partial replacement for all the salt you sweated out.

  20. I have worked at a solar power plant for over 20 years now here in the Mojave Desert. We create enough heat in the summer to make over 40MWe at just one plant of five at my site. There are 9 plants in exsistance for the last 17 years, ranging from 13MWe to 80MWe rating..we do more in summer usually.

    Long ago it was rumored that they were going to build one near the Salton Sea in Southern California to desalinate the water….never happened…YET. Never know.

    For the first time in 17 years a new solar thermal power plants( solar trough) came on line in Boulder, NV. Many more are in the final designing stages in California and other USA southwest states along with Spain.

    But this is nice too for the individual. All you have to do is just install a drain line/valve around the rim. ( sorry if someone pointed this out earlier and I missed it)

    I have a solar hot dog cooker that is based on a Parabolic Trough like my solar power plants. Works well too.

    Solar Homer Simpson

  21. Raf, thanks for the voyage of the mimi reference. I haven’t known the name of this show that I had a foggy memory of in my mind for the longest time. All I can remember is learning about reading a map at some point along their journey.

  22. bitje: This is the company I know that developed the “rabbit” filter:


    The product description (pdf) can be found here:


    I’m currently working in Cambodia, which is how I know about them. One of the great selling points of this organisation is they use the market to reduce poverty. The benefit on people living below the poverty line is huge: seeing people fighting their way out of poverty instead of relying on donors / charity is one of the greatest experiences of my life so far.

  23. this is not a scalable system. the area to water yielded ratio is nowhere near enough to support a population that living off of subsistence-levels of water intake. if this were halfway practical on a large scale, it’d have been implemented a long time ago.

  24. Nice idea/design but it’s probably worth having another look at the demographic you’d be selling these to. You’re looking at the poorest of the poor, say for example refugees in Dafur, various areas of sub-sahara africa … I can assure you they don’t have a spare 20 bucks sitting around to buy one let alone enough to provide water for their families.

    If you sold these to aid agencies they might make it down to the people who need them but thats about it.

    As for providing jobs … again it’s a pretty big investment for a very small return, I highly doubt you’d ever even come close to paying these off over their lifetime.

  25. Yeah, this is hardly a new concept. You can do the same thing with a single plastic sheet (which would be even more portable.

    I like what they are trying to accomplish, but hardly new.

  26. There are cheaper ways to accomplish this, such as the method Nick describes (comment #7), which is referred to as a “solar still” in the SAS Survival Handbook. It is presumably a long-known technique that was probably effective even before the advent of plastics.

  27. Regarding bacteria accumulating in the water collection area. I don’t think so. The collected water is highly pure. The inner surface of the cone is constantly protected and constantly cleaned up by the distilled water. Bacteria would have no nutrients to feed on.

  28. Nice, simple design, and portable – but it’s just an upside-down solar still. If you run the device this (above) way up it works the same, but it coats the bottle surface with impurities as the evaporation occurs. The distillate flows down over this and collects a small amount of the impurity as it pools and again as the liquid is poured off.

    If you dig a small pit, then put a collecting dish at the bottom, then cover the hole with clingfilm (or any waterproof sheet) and put a small pebble in the middle to focus the drips, the purity is better – and that design is decades old. But it’s not portable without dismantling the device, so this version has that big advantage.

    Thanks for showing it :)


  30. ingenious…invention, uhh no

    Solar stills have been in use for hundreds of years (even cone ones).

    Plastics release toxins, hormones, and cancerous compounds (among other “nice” things). Under heat these are all released much faster.

    So good luck if plan to drink hot plastic residue (you’ll need it).

  31. Dave and Rob you are wrong. The depth of the water has nothing to do with it. The heat inside the cone creates humidity. Which causes condensation to form. If it were black it might work better. Water in the ocean is constantly evaporating or condensing. It could be made huge and it would work. The height of the cone I’m sure has to be just so close to the water to work most efficiently. But it isn’t practical for trying to make water for a city. Hydro, wind turbines, or solar electric power can be used to clean up water much faster. In large quantities and be cheaper in the long run. But for it’s intended use it is great!

  32. It will take a loooong time for condensation to fill a glass of water like that. Hope your not to thirsty

  33. dudes – can’t we all just get along – i mean who of us makes our own drinking water ? one experiment is worth a thousand opinions – someone here who thinks they are a genius should buy some and take them to Africa and try it. otherwise quit knocking peoples ideas who are just trying to help. get over yourself already, i mean gosh man your giving me an advil moment

  34. Didn’t they do something just like this in Voyage of the Mimi?

    Oh, 5th grade… how I miss thee…

    [Not knocking the idea, btw, just reminiscing.]

  35. The filter described on the IDE Cambodia website appears to be a ceramic water filter. A small scale ceramic filter designed to be produced locally in third world countries with essentially no modern technology was developed in Australia. Here is the website information:


    This looks interesting. I would be interested in the testing done to show removal efficiencies. Also, it is unlikely that this would remove other organic or inorganic compounds. The website does link to a pdf file that explains how to make your own. Presumably one could use a charcoal grill to cook the filter rather than cow dung if the latter is not available (or you’d rather not burn cow dung).

  36. I think it is great people are considering trying to find help for others . This is always to be admired and commended. It might not be THE ANSWER to problems,but its a good start and gets the old noggin thinking on it again.
    I have been in search of a salt water or fresh water,drinkable water maker that is travel worthy in case of emergencies. Portable .
    This is a consideration,but I was hoping for the one the military uses by taking air and making water out of it in the desert with no water available. Why is that not out to be had for all?
    Maybe we should look at the ones who keep these people in the situations they are in.
    The govts act like they are helping,but they only are reassuring their needed by that country for aid and help and can exploit them for resources as pay back,etc.
    A constant needy one in guise of helping them with organizations they set up to launder goods and money thru in guise of aid to poor nations,get the donations of generous countrymen to donate funds and pocket most .Minute amounts really ever get to the needy ones.
    This pretend help while raping them is actually keeping them down.

    If you truly are helping a country or person,you get them to where they can be self reliant with out you and not dependent on your kindness for ever.OR fake attempt at providing it anyway. Looks good on paper and in media as they tell the m edia what to cover and scinetists dont get funding on anything unless they say so,we really are stupid to let them have so much control over the world. YOur schools,scinece,technology,info sources,all controlled by the same ones who are undoubtably ensuring your incapabilty to get them out of thier nice comfy throwns. They sure wont be giving you the keys to the Flying disks,but rather teaching you false so you might not ever stumble upon it and controlling them who are wiser than most by funding and reputation control thru organizations and fellowships all aimed to keep you dumb and down. Just not as down as some are.
    We all are down and will stay down or downer if they have anything to do with it. Why we let it go on,is beyond me.
    Harping on elections as if they have ever or will ever change a damn thing with empty promises never kept and corrupt systems ensuring their people are all in place with them.
    Why has not anyone ever got the damn advisers who stay in office for decades out of there first? That might be a good place to start and then learning that Democracy is not what the USA was founded on.
    It is what you do NOT want.
    AS uaual we go thru life existing on what they who mean to keep us down tell us and never question anything. DUH ENOUGH ALREADY.
    Are we men ,humans, or ducks ,quacking our way thru a meager existence without ever using our noggin.
    I am ready to LIVE, NOT EXIST to have a roof over my head and never think about anythign other than thier news fed to me,the gossip talked about by fed coworkers by them,10-12 hours a day thinking of little but shit and then so exhausted from earning from them at piddly wages,for roof and food over our heads ,we are incapable of mustering any of our own thoughts or ideas.
    SLowly we are discouraged to have free thoughts. Bombarded constantly by media and hype of nonsense. The damn media should all be hung for their participation in this gross mind mushing of the world.
    PEople. ALl shoudl have food and water,not only some.
    We must not look the other way anymore . It is this planets shame,and if other worlds are looking in,why would they ever help a planet that lets thier own die and suffer needlessly while some have so much they could never use it all. Then majority of time is spent doing little good for planet and only in stupor of uselless jobs that better noone but few and keep this haywire chain in motion.
    Then all helpless eventually and the few do at will with them and they only live for them. Never for eachother or the betterment of mankind. What is this planets good? They have only showed beasts,cruelty and lack of common sense or abilty to rationalize what is being done to themselves. Land of the free,ha, They are more a slave now than ever. Yet they do not see.

    MANKIND is SOVERIEGN, not WASH DC AND THE VATICAN as they claim are the only ones on earth sovereign.
    (if that is not a flag most wont see )(They put themselves above you and God)
    Whether your man enough to admit it yet or not. The rest of us are not so big headed,its too apparent we let this get out of hand.
    Once we can overcome the ego enough to admit our faults at letting this get carried away and then perhaps trying to stop it,well,it sure wont be getting any better.
    You Might want to grab a cone,might need it ,at this rate.
    Stop believng their paid or bought media ,info sources,and use some damn logic.
    If I keep doing this at this rate,what is the inevitable conclusion?
    ,Not the fairy tale one they feed you. But the obvious one if you thought about it. THINK FOLS AND BE NICE TO ALL MEN AS ALL ARE CREATED EQUAL AND ALL ARE CREATED BY A SAME HIGHER POWER and I think we should stop doubting he wants us all here as he keeps creating more people.
    Might be best to stop killing what the creator creates.
    Has not worked for thousands of years.
    Maybe a new game plan is in order? YA think?
    OH majority of all the minds in the world are not thinking,I forgot.
    Gee we get far this way,Ya think?
    Watch this entirely through will ya ,then think some on it. Please

  37. Spanich:
    Este invento está en el manual “Scultimo para Muchachos” de
    Lord Baden Powell of Gilbert, Claro que con lo rudimentario de los
    años 1880 al 1920. En nuestro desierto de Atacama, se usa este sistema.
    He dicho

  38. Watercone is not enough to drink but I would bet it would help irrigate some vegetation somewhere possibly like drip irrigation? I would guess that it might make a decent hyroponic facility where initially food and water resources are challenging but in the end with planning and creativity why not? I can imagine a collection rig with a series of these cone/ cells that could be buried underground where the temperature might extend the life of the collected distillate. Consider too, the use of borosilicate glass that is a lot tougher than most people know. The water collected should be collected frequently and in doing so prevent cumulated bacteria to contaminate the product. I wouldn’t doubt a more practical application will be devised to employ this cone. I just don’t think it has been thought all the way out yet. Too many negative comments shoot it down.
    Oh and the United States isn’t a Democracy but, a Republic. We’re being fleeced by a bunch of rhetoric and as long as we buy into it complacently well, this is as good as it gets. I kind of wonder if Uncle Sam died on us?

  39. I think the jury is still out on plasctic leeching and the effects heating has on the chemical makeup of certain plastic materials. This water may be ok for emergency, or irrigation and hygeine, but not for long term human consumption.

  40. WOW!!! That has got to be the coolest thing I have ever seen in my entire life!!

    P.S. re: Am I Alone Here. What the hell’s in your water?

  41. ^^^ salt. you can do this without that, same thing with urine because it only evaporates the PURE WATER out of a substance, but when theres a clear object in the way of evaporation the water condenses on the clear object. you dont really need a funnel, but atleast needs to have a dripping point if its inverted. i saw it once on survivorman/man vs wild.

  42. I remember seeing this same idea on Mr Wizard or one of the other kids science shows back in the late 80s-early 90s. Not particularly practical over the long term because it yields such a small amount of water. Filters or a still would be best if you need to provide water for an extended time or for a population of more than one.

    As for the criticism of distilled water, that’s complete nonsense. While your body does need salts and minerals, lack of salt can kill you. However humans gain most of their salts not from water but from food. So unless the person in question is drinking distilled water and not eating in an situation where they are losing salts quickly (heat, exercise, etc) over a good length of time (or for that matter drinking water of any sort in that situation) then they aren’t going to be harmed.

  43. I want to make some points like,
    The processes of evaporation and condensation taking place at atmospheric conditions have different and conflicting requirements. Just check out how it is done in laboratory.

    The problem I see with cone design is that

    1. The path for the energy (solar rays) to reach the working point that is surface of unclean water, is through the point where condensation is supposed to be taking place.

    2. The Cone does makes evaporation and condensation in this design but the potentials are never utilized i.e. the efficiency of the design (apparatus) is Low.

    3. Cone does provide part surfaces exposed at different angles to sun in full range like at near perpendicular to near parallel. So one gets only part performance.

    4. Fast evaporation and condensation otherwise taking place naturally in open situations involeves movement of air above water surface and prevailing “humidity” conditions.

    Put all above four points together and that basically concludes the concept is not exactly suitable for any full scaled-up community application. The Cone is just OK as stop-gap cutomised solution for near desparate conditions.

    None the less it is an innovative and good design.

  44. this is really an old design, having originated with the pot still, and maybe as old as several thousands of years. the only real difference i see is it’s used for water w/ evaporation …. and that production could be increased by including an output on the lip to allow for continuous production….. as in the original potstill design…..

  45. I saw this about 40 years ago in a childrens book, it is called a solar still.
    They used a sheet of polythene over a pit filled with leaves or any damp stuff. You put a weight like a stone in the middle of the sheet to form a cone shape and collect the drips in a cup in the pit. I don’t see why it would cost 20 euros, It wouldn’t cost any more to produce than a disposable drinks bottle

  46. This is great !! Eventually, when i would crash with a plane in a desert island in the middle of the Pacific, I will remember this !! Do you know if the shipping area covers the Northern Pacific and South Pacific ?

  47. Hey…
    Just wondering if it would work in the fall and how long it takes..We have to do a science project on filtering salt water into potable water. And we have to demonstrate in class. This seems like a pretty classic answer, we have decided ot go woth it..any tips on how we could speed up the process or any other tips.thx!!!

  48. This is a pretty handy thing to have if you’re stuck on a beach. Take about half-a-dozen, and then when your water supply runs out, haul up some salt water and distill it.

  49. Some thoughts and analysis on the high cost of these, compared to what people actually pay in the developing world.


    It looks like they’re only useful where safe water is exceptionally expensive, or simply unavailable. And even then, I’d be thinking about whether there are other ways of purifying the water – or perhaps mass producing these things for more like 1 euro or less each – which looks like a more reasonable price for mass-produced pieces of plastic, albeit very cleverly designed pieces of plastic.

  50. just a stupid question, but wouldn’t it be easier to have the water slide down to a trough on the inside rim, so u wouldn’t have to flip it over?

  51. €20 = USD$31. That’s what most poverty stricken families make in over a month. If it’s designed for the world’s poorest, it will have to sell closer to $10 to even give those people a chance to afford it. For us it may be cheap, but we can’t judge other people’s buying power by our own standards.

    It will need to be mass produced in the needy country where it’s to be used in order to lower the price to affordable levels.

  52. This item should be made from a non-BPA plastic.
    BPA is responsible for many health hazards.
    I would only purchase or recommend this product if this change was made.
    However the design is fantastic.

  53. Fairly simple, I was one of these created on a survival show. The salt can also be used as a supplement or seasoning. A reflective bottom might improve the efficiency though.

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