Separating water from salt

Bill Siegle

Bill Siegle

Knifemaker / Craftsman / Service Provider
Joined
Oct 3, 2000
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So last week I was camping and something that I thought of was can ocean water be desalinated via transpiration? I know filters exist but my theory is that if you applied the technique of using a clear plastic bag filled with leaves and left in the sun, water is evaporated out of the plant and collects on the bag. If you were to place a pot of salt water in a clear bag would evaporation seperate the water from the salt? I watch all these tv shows where people are on beaches but have no potable water. Coming up with a way to make water from what you have available could save you from those first few days of suck that most never really recover from. Now keeping with the TV premise, I would not want a clear trash bag as my "one item" but maybe having one in the kit would make a lot of sense.
 
Yes, you absolutely can. Lifeboats often have one or two solar stills that basically do that. Here's a picture.

landfallnav_2268_220000576


Lots of hoses, but still a plastic pot with salt water and a bag to catch the condensate.
 
Thanks for the info! I'd not seen anything like that before.
 
Admittedly I have never tried, usually when I am on a beach it's a bit crowded. But I was taught that if you dig down deep enough to hit water on a beach several feet back from the high tide line, then the water will be mostly free of salt.
 
there are locations where fresh water can be found if the beach is formed by dunes, you can gather the runoff from farther inland. As far as solar stills go, they are pretty tough to use, and even under ideal conditions, they don't provide much. One way to add efficiency is to use a lens to focus light onto a small area, and add very fine charcoal powder to the water. the individual grains can boil off the water much more efficiently. Worth knowing about if you needed to make one.
[video]https://youtu.be/ved0K5CtmsU[/video]
 
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You got your answer. That's actually called distillation.

As far as your filter comment. It's not that easy as the water molecules are larger than the salt molecules. So you have to another method. It exists and yields fresh water and saltier water. The large desalinization plants do this but it's very electricity dependent. Requires a lot.
 
The Destillation unit in the picture will give you a cup of water a day. Let's hope there are no waves rocking the lifeboat.

There are reverse osmosis hand pump filters which should be able to desalinate water.
Last time I read about it was in the 90s in some outdoor catalogue. No clue if still around. Luckily there is Google.
 
While definitely not an inexpensive solution the Hydrowell system can convert salt water into a drinkable sports drink using forward osmosis. There is a tactical supply near you Bill who sells them if you want to call and inquire more
 
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I've often wondered how you turn sea water in drinkable water myself . Too bad you can't just boil it and or use puro tabs
 
Drinking distilled water long term robs you of the minerals otherwise found in water. For better or worse.
 
sideways said:
Drinking distilled water long term robs you of the minerals otherwise found in water. For better or worse.
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You're correct but they can be found elsewhere. And I'm think distilled for only emergency scenario which, hopefully, wouldn't be long term.
 
If you needed salt, a half mouthful of sea-water would do, and you pick up plenty of minerals from food normally. Its not hard to find a balance, you just need to take care. The guys who live on gatorade run the opposite risk of those who only drink distilled water. At least with distilled water, you can add minerals back into your diet, if you are stuck with a electrolyte filled drink, then it would be harder to hydrate if you went over.

there are a few reverse osmosis hand pumps on the market but they are very expensive. quite effective if that's what you need. I'm sure there are other units for use on boats with dedicated power systems. and there are house systems for softening water.

For flat out ease of use, I think that distillation by boiling would be the easiest method, as long as you can build a boiler and catch the steam in some way. The main advantage is that you don't need to be terribly efficient. There is plenty of water, so its not like you have to catch it all. you can still use sea-water to cool your condensate, and you don't even need a full rolling boil (although it would help the speed).

Digging dunes for water is pretty much the same as bore water, its just shallower. you are collecting rainwater that has settled into the sand. While they are not legal for use in parks anymore because removing the water destabilizes the dunes, there is a thing in Australia called a water spike, (which is pretty much just a plastic pipe with holes drilled in it) for collecting water from dunes. From what I've heard, they work quite well.
 
mistwalker said:
Admittedly I have never tried, usually when I am on a beach it's a bit crowded. But I was taught that if you dig down deep enough to hit water on a beach several feet back from the high tide line, then the water will be mostly free of salt.
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That is a function largely of how much rain is falling. In the Summer in So Cal (even before the drought), salt water used to infiltrate well inland. Public water was distributed underground and accessed by wells. People were warned to used bottled water, especially for babies.
 
gadgetgeek said:
If you needed salt, a half mouthful of sea-water would do, and you pick up plenty of minerals from food normally. Its not hard to find a balance, you just need to take care. The guys who live on gatorade run the opposite risk of those who only drink distilled water. At least with distilled water, you can add minerals back into your diet, if you are stuck with a electrolyte filled drink, then it would be harder to hydrate if you went over.

there are a few reverse osmosis hand pumps on the market but they are very expensive. quite effective if that's what you need. I'm sure there are other units for use on boats with dedicated power systems. and there are house systems for softening water.

For flat out ease of use, I think that distillation by boiling would be the easiest method, as long as you can build a boiler and catch the steam in some way. The main advantage is that you don't need to be terribly efficient. There is plenty of water, so its not like you have to catch it all. you can still use sea-water to cool your condensate, and you don't even need a full rolling boil (although it would help the speed).

Digging dunes for water is pretty much the same as bore water, its just shallower. you are collecting rainwater that has settled into the sand. While they are not legal for use in parks anymore because removing the water destabilizes the dunes, there is a thing in Australia called a water spike, (which is pretty much just a plastic pipe with holes drilled in it) for collecting water from dunes. From what I've heard, they work quite well.
Click to expand...

Rule of thumb, I wouldn't reccomend drinking sea water ever. Instead, eat a piece of bull kelp or seaweed, they are packed with tons of vital nutrients to get you back in the game without the potential for shutting down ones kidneys.
 
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