Sea Water

[Lodian]

Was down the beach camping the other week with a couple of friends and our 3 2l bottles of water ran out. Luckily one of our friends houses was only a full 10 minute walk away so we refilled. But if we wernt that close, what is the best way to deal with sea water? Does a millbank have any effect?
Ive heard of reverse osmosius pumps but at £100 i dont think so.

Thanks for the help
Ryan

 

[BOD]

The only thing to do is distill the water if you are not using a pump or give each other a salt water enema

 

[Ahjno]

Was down the beach camping the other week with a couple of friends and our 3 2l bottles of water ran out. Luckily one of our friends houses was only a full 10 minute walk away so we refilled. But if we wernt that close, what is the best way to deal with sea water? Does a millbank have any effect?
Ive heard of reverse osmosius pumps but at £100 i dont think so.

Thanks for the help
Ryan

A millbank bag will not work at all: it's intended to filter small / fine debris out of the water. Sea water contains salt, but it's a solution on molecule level - hence these will pass through the extreme fine weave of the mill bank bag, as these are bigger than molecules.

Another option would be, as you mentioned, the reverse osmosis pump. But these are pants: the energy - clean water ratio is just to high to justify in my book (you keep on pumping ... and pumping for a minimal amount of water).
Only good in a lifeboat as a last result (pump at night to prevent unnecessarily loss of sweat (water)).

You could dig a hole (25m?) above the high water line, there you should be able to find some fresh water (sweet water 'floats' on salt water). Check some survival guides for more info (don't think it's in bushcraft books).
I tried it several times without any result ...

Distillation:
- You could dig a whole, saturate the soil with sea water, place an empty container in it, cover with clear plastic, place weight just above container.
Current concensus is that this method isn't working (good enough). (There's an episode with RM in the desert: he only got one mouth full of water over a period of 24hrs from this method - though he didn't saturated the ground with sea water, but placed some cacti in the hole).

- Start a fire, place container with sea water and lid on fire, surgical tubing from this container to a second one - nicely covered in sand (to get it as cool as possible - so the vapourised water condensates).
(You can improvise this method with 2 lemonade bottles (1.5 - 2ltr) and using the sun).

Life boats carry sea distillation kits: plastic made, round piramid-ish in shape, need to inflate them, fill base with sea water, sun will do the rest - they are pants at rough sea though. But I reckon they work on land.

Catch dew with your tarp ...

HTH

 

[kb31]

i had a idea a bit ago but never tryd it out-
make a solar still and soke in sea water
then dig a deeper hole next to it
2feet away or something and light a fire in it to speed things up
it might work but would take up alot of time
just a mad idea

 

[Jackdaw]

You could boil the sea water. Then use a capture device to divert the steam into another pot. You should be left with salt in the bottom of the original pan and plain water in the capture pan. We did this at school yonks ago. It might require more than one boil though, not sure.

 

[Boatswain]

Dr Alain Bombard crossed the Atlantic in a rubber dinghy living on plankton and weeds and stuff, he supplemented his drinking water with sea water and rain water.

certainly in hot climates the body needs salt any body know how much?

Cheers Roy

 

[BOD]

Yes but Bombard started drinking sea water immediately when already fully hydrated.

If you wait till you are dehydrated it may kill you

 

[Martyn]

A variant of the solar still...

Take two large containers or bottles, fill one with sea water and connect to the other with a couple of feet of hose pipe, seal the join where the hose goes into the bottles with gaffer tape. Bury the empty container just beneath the surface in the side of a sand dune and leave the one full of sea water exposed. Leave it alone. One day later, the sea water will evaporate out of the exposed bottle, travel through the hose pipe and condense as pure water in the cool, burried bottle. Decant the fresh water and re-bry the empty bottle, wash out the saltwater bottle (which will now contain a strong salt solution) and refill with sea water. Be carefull not to contaminate your fresh water bottle with sea water. How much fresh water you get will depend on a number of things like how hot it is etc. You may have to make several of these to get enough water on a daily basis to live off.

 

[match]

I've done the following on the beach before as an experiment and it was quite effective so I thought I'd share.

Build a big fire, fill it with rocks (be careful here, as some rocks like sandstone can be explosive when heated!) and let them get nice and hot. Rake the fire away and leave a pile of hot rocks sat on the sand. Rake these rocks under your tarp which you've set up at an angle pointing a corner down to a collection container. Get a bucket of seawater and gently pour onto the rocks - the steam should rise off in big clouds, condense on the tarp and then run down to the collecting vessel.

Its not the most effective way of doing it, and you don't get much return from your investment, but you don't need much in the way of resources (you could replace the tarp with a waterproof coat or a rocky overhang for example, and the collecting container with you

 

[Kane]

Read a book a while ago where a guy walked around the Baja peninsular using a still to provide all his drinking water (from seawater) nothing high tech IIRC I'll try and find the title ....

May have been this'un :-
Into a Desert Place: A 3000 Mile Walk Around the Coast of Baja California by Graham Mackintosh

It'd be interesting to see if someone could come up with an adapter kit for a Kelly Kettle to allow distilation where sea water is available so that you don't need to use your fresh water supply during your trip.

 

[RobertRogers]

Wow, I really like the two-bottles-attached-to-a-hose-sitting-in-the-sun method! Gonna have to try it on the next sunny day. If we ever have one that is...

 

[kb31]

i've seen it on a sas survival show the 2 pop bottles thing
but they did it with urine
did't think of trying sea water

 

[Martyn]

i've seen it on a sas survival show the 2 pop bottles thing
but they did it with urine
did't think of trying sea water

I think that's where I got it from. Worked well for them, I seem to remember. They got good volumes of potable water from urine, ...same principle with sea water. I've never actually tried it meself though.

You'll be able to see roughly how much fresh water you have distilled without digging the bottle up, by keeping an eye on how far the seawater level drops in the other bottle.

 

[SMARTY]

Lodian there is a product on the market called the XPack. it uses osmosis to make sea water safe to drink. There is also a fresh water version. The XPack produces 1 litre of safe water in 8 hours. I will remove 100% of the salt, as opposed to 98% for reverse osmosis pumps. it is now in use by the RAF Typhoon squadrons. I demonstrated it at the Cornwall RV (fresh water version). It comes from the States. If you are on the coast start the XPack or a number of XPacks working before you run out of drinking water.

 

[Ahjno]

If you don't have a hose, you can also connect the bottles with duct-tape at their neck / open end. Be careful though when you place them horizontally not to spill sea water / urine in the clean bottle.

 

[w00dsmoke]

Lodian there is a product on the market called the XPack. it uses osmosis to make sea water safe to drink. There is also a fresh water version. The XPack produces 1 litre of safe water in 8 hours. I will remove 100% of the salt, as opposed to 98% for reverse osmosis pumps. it is now in use by the RAF Typhoon squadrons. I demonstrated it at the Cornwall RV (fresh water version). It comes from the States. If you are on the coast start the XPack or a number of XPacks working before you run out of drinking water.

I've done a search on the internet but can't find it anywhere...do u know a supplier?

 

[Glen]

I think that's where I got it from. Worked well for them, I seem to remember. They got good volumes of potable water from urine, ...same principle with sea water. I've never actually tried it meself though.

You'll be able to see roughly how much fresh water you have distilled without digging the bottle up, by keeping an eye on how far the seawater level drops in the other bottle.

I've not tried it but I've had an idea that ( if my theory is correct ) should improve distillation yeild in a given time frame.

Fix a condom ( even better if it's a black one ) onto the tube, gaffa tape and paracord would probably both be needed. Feed condom into first bottle and fill via tube. Seal other end of tube to second bottle and put in cool shaded place or bury underground.

The idea being that having the sea water/urine in the condom should isolate it from the walls of the bottle that are being cooled by the outside air and any breeze. A secondary effect would be that the unpurified water would have very little air space above it in which the distilled water could form droplets and run back into, therefore a larger portion should travel along the tube and collect in the second bottle.

I've also thought that a similar setup, black condom in clear bottle, might be useful to melt ice/snow for water in colder conditions without wasting fuel.

As I say, at the moment it's theory in my head, so don't rely on me being right in a survival situation, but definitely something worth trying if your experimenting with the normal method anyway.

 

[Ahjno]

I've done a search on the internet but can't find it anywhere...do u know a supplier?

Try searching on "Xpack" and "desalination"
http://www.sea-pack.com/seapack.html

 

[Ben_Hillwalker]

In a true survival situation (ie survive or die) you can stretch out your fresh water supply by mixing with seawater at the ratio two parts fresh to one part salt.

Prolonged usage will not do your kidneys much good which is why this is more a survival strategy rather than a bushcraft strategy.

 

[Tengu]

If you were in a hot climate and sweating a lot, the salt might be a neccesity