How to Desalinate Seawater





Introduction: How to Desalinate Seawater

About: Still sort of a beginner.

I can't believe there's a whole ocean full of water but we can't use it.So here's a way to desalinate seawater.It is best to try it on a sunny day early at sunrise;it will be done more or less in the afternoon.

Step 1: Prepare the Container

Use the big container and put the round black lid inside it.This is to atract sunlight.

Step 2: Add Recepticle

Place the small cup in the middle of the container on the black lid.

Step 3: Add Saltwater.

Add some seawater that you want to desalinate in your container but don't spill it in your cup.

Step 4: Cover With Plastic

Put the plastic over the container and fasten it with your elastic band.

Step 5: Small But Very Important Modification.

Add a small weight on the plastic right above the cup so that the plastic points down to your cup.

Step 6: Wait.

Wait for the water to evaporate, condensate on the plastic and trickle down and into the cup for you to drink.



    • Oil Contest

      Oil Contest
    • Creative Misuse Contest

      Creative Misuse Contest
    • Game Life Contest

      Game Life Contest

    102 Discussions

    i will try this if right well this can be a very money saveing for me

    Definitely a useful tool in a survival situation, but a solar still isn't something I would recommend solely relying on for water in a survival situation. They take a long time to purify a comparatively small amount of water and you're more likely to end up with far less water to drink than you expend over the course of waiting for it.

    A relatively simple way to expedite the process is to use a double boiler over a fire made of two metal containers ( you can substitute soaked birch bark cups or leather hides in an outdoor emergency, or really any container that won't burn or melt. ) and any sort of cone ( again, whatever yo can come up with. ) that you seal to the container with whatever you can find to keep the steam from leaking. By putting the whole deal over a fire, you will lose some evaporation through the seams in your makeshift still, but the increased efficiency of the whole thing will more than make up for it, with the added bonus of giving you a warming/signal/cooking fire to work with through whatever disaster you find yourself in.

    9 replies

    Awesome. Do you think you could do an instructable showing this process. And i have a simple question. Can you drink rain water collected or would it be wise to filter that as well. Thank you for your response

    Drinking rain water should usually be safe, but if you have the ability to distill or purify it, you should still do so. While it will generally be "clean" of pathogens, it does collect some level of dirt and other impurities like heavy metals as it falls to your collection vessel and in a survival situation, you're not going to be sure that your collection tools are clean. So while you can drink rainwater without a big risk, the number of things it contacts between falling out of the sky and going into you can result in potential sickness. Part of the point of purification that's often overlooked in discussion and survival guides is that you're not only purifying your drinking water, but also purifying the container you're drinking out of.


    I don't understand. Do you mean that the enemy might find you?

    I believe he's referring to situations like being stranded at sea, or similar where fire would be either too difficult or dangerous to make, but those sorts of situations are VERY far and few between. As a rule, a fire is one of the best things you can have under survival conditions for a variety of reasons.

    Yes i completely agree. But. And this of course is a big but. If you were in end of times say and it was all out anarchy. She makes a valid point. What would be a trick for a fire to do the water desalination and keep the fire hidden. IE no smoke no signals that i dont want people to see that im there and have supplies for you to kill me for. Far fetched but valid.

    Here is something that I was taught in the survival course when I was in flight school: 1.) In beach situations find the high tide mark, 2.) Pace off 100 "yards" inland from that point, 3.) Dig down into the soil until you hit "water", 4.) Collect that "water" [it should only be a ~.5% to 1% saline solution (normal salinity is 3.5%)], 5.) Filter that collected water through any piece of wadded up cloth, 6.) Then if possible construct a solar still using that "water", 7.) Your solar still will be much more efficient & the untreated water can be used for cooking and personal hygiene.

    Awesome response. Taking notes my friend

    ewbray, that's absolutely a good addition wherever possible. Anything that helps with reducing the amount of energy and time expended in purifying your water is a technique worth adding to your mental tool kit.


    11 months ago

    I saw a documenrary from Australia when I was a kid, Henry Butler's In the Wild, where he showed this in the outback. Not that I could use it here in Europe, but it impressed me non the less. And recently R Redford did it in the movie All is lost (great movie for sailors btw).

    I found an article that confirms this can be done. Thanks for the instructable.

    Once the water has been condensed and captured in a jar, put a lid tightly on the jar, and let that sit in the sun to cook it, to kill pathogens/parasites. Of course, this requires planning ahead, and having multiple jars to cycle through the process.

    Could make a tray with glass over it, and have the condensate run downhill into a catch-trough inside the tray, which runs out a drain into a container, to make more clean water per batch. If you use glass containers to store the water, it can be heat-purified by tightly lidding the jars and putting those in the sun to heat up. OR, use emergency small-branch filters from trees and shrubs that have longitudinal fibers, and are non-toxic....use the stick to plug the bottle of water, turn that upside down over another container to let gravity filter the water through the stick, to remove parasites and germs. One-time use per stick.

    6 replies

    I don't see why we should do that. The condesated water it's a clean one.

    It would be nice if we still had clean rain.
    But we don't...almost anywhere in the world now, it's contaminated by various heavy metal particles, as well as chemicals, one way or another.
    During distilling, be it solar or boiler method, much of the particles, germs, and chemicals remain in the cooker.
    BUT...there are still some hazardous chemical residues of certain kinds, that are small enough, light enough, and bond with water well enough, that they travel along with the steam or condensate, into the collection bottles.
    Therefore, it's important to, at the very least, use an activated charcoal filter on the distilled water, to make it fit for potable use.

    That would only be necessary if those chemicals had a close ebulition temperature at the same pression as water. I don't know, maybe there is.
    The chemicals that are dragged by the rain, as you mentioned, were already in the atmosphere. I don't have knowledge of a chemical bounding to water, in which would mean a chemical reaction, but it would be no longer water, nor sharing its propertys.

    I do understand your point of view, there could lots of contamination sources, including the cup itself. But you should understand that evaporization means that the molecoles of water are free, not bounding to other chemicals. If some of those chemicals also evaporate, it would be minimal in comparassion with the salinated water.

    Chimonger, letting it 'sit in sun, to 'cook' will NOT kill the pathogens / parasites. On the contrary: like with most pathogens / parasites, the warmth will only make them flourish. (Basic logic: If they weren't 'cooked to death' under the sun, while in the sea - why would it be any different while being under the same sun, in your garden)? If you want the water to be sterilised and parasite free - it needs to be boiled.

    Closed container in the sun, can result in water that can cause a blister. That's hot enough to kill pathogens. Caveat: Allow contents to solar-cook long enough, to kill the pathogens. I'd give an educated guess, that once the contents are too hot to touch the jar, leave it for at least 1 hour.
    The sea is a huge open volume of water. By your 'logic', solar cooking would never work....except solar cooking is real, and has been real for a very very long time. If one can heat liquid in a closed jar, hot enough to blister skin or flat-out boil it, it can kill pathogens.

    Really,logic.....The sea is an enormous body of water which takes a lotttt of heat and time to warm up, it's not the same logic as a small container in a garden at all. Same sun, different volume. I would tend to agree that evaporation should be fine, water molecules are separate more or less in a gaseous state and would not act as a medium to transport bacteria etc. Although perhaps cross contamination from the surface it is condensing on could occur.