How to Make a Solar Water Purifier

Marooned with no fresh water.  But wait!  Check out the materials you have on hand!
Marooned with no fresh water. But wait! Check out the materials you have on hand! | Source

You are stranded on a dingy, your ship just having sunk. You are in the middle of the ocean with 'water, water, everywhere, but not a drop to drink'. The sun looms high on the horizon. The heat is oppressive and the salty sweat drips off your tired body. Becoming more dehydrated by the minute, you look out to sea, hoping desperately for a rescue vessel but none is in sight at the present time. You realize that you have only a day or so of survival without water before your moisture starved body succumbs to the elements. Suddenly, you remember a lesson from a high school science class. It looked at obtaining pure water from salty water. If you remember correctly, it required only a few meagre materials. Checking through the possessions you managed to salvage you find a large bucket, a small cup and the remains of a plastic tarpaulin. A piece of rope and some coins from your pocket are the remaining materials required to fashion a solar water purifier. Your survival is looking better as you have more than an adequate supply of solar energy to fuel your purifier. Your memory of the water cycle provides hope as you realize the power of the sun's heat to evaporate water from the sea. Now, how to collect that evaporated, pure drinking water to quench your thirst. Read on to discover a solar purifier, able to collect that life saving drink, that you could make in a pinch if ever shipwrecked or marooned by your crew on a tiny island in the sea!

Main Materials for the Solar Water Purifier

Large bowl, small glass, plastic wrap and salt are the main materials for the solar water purifier.  I also used cellophane tape and a small steel ball.
Large bowl, small glass, plastic wrap and salt are the main materials for the solar water purifier. I also used cellophane tape and a small steel ball. | Source

Materials to Make a Solar Water Purifier

  • water
  • sea salt or table salt
  • large bowl
  • short glass that will fit inside the bowl and be shorter than the top of the bowl.
  • plastic wrap
  • tape
  • small weight like a screw, nut or small rock

How to Assemble the Solar Water Purifier

Click thumbnail to view full-size
Adding salt to 3 cups of water.Mix until the salt dissolves in the water.Centre the small cup into the large bowl and pour the salt water carefully in the bowl around the small cup.Put the plastic wrap on the bowl and press against the rim of the bowl.  Place a weight, in this case a steel ball, in the centre over the small glass.Tightly secure the plastic wrap to the bowl with tape.Fully assembled solar water purifier.
Adding salt to 3 cups of water.
Adding salt to 3 cups of water. | Source
Mix until the salt dissolves in the water.
Mix until the salt dissolves in the water. | Source
Centre the small cup into the large bowl and pour the salt water carefully in the bowl around the small cup.
Centre the small cup into the large bowl and pour the salt water carefully in the bowl around the small cup. | Source
Put the plastic wrap on the bowl and press against the rim of the bowl.  Place a weight, in this case a steel ball, in the centre over the small glass.
Put the plastic wrap on the bowl and press against the rim of the bowl. Place a weight, in this case a steel ball, in the centre over the small glass. | Source
Tightly secure the plastic wrap to the bowl with tape.
Tightly secure the plastic wrap to the bowl with tape. | Source
Fully assembled solar water purifier.
Fully assembled solar water purifier. | Source

Making the Solar Water Purifier

  1. Add 4 tsp of salt to two or three cups of water.
  2. Stir until the salt dissolves.
  3. Pour the solution into the bowl.
  4. Put the short glass into the middle of the bowl. The glass should be above the level of the salt water while at the same time being shorter than the bowl. Adjust water level if necessary.
  5. Cover the bowl with the plastic wrap sealing the wrap to the bowl tightly with tape.
  6. Place the weight on the plastic wrap directly over top of the small glass.
  7. You may need to anchor the weight with a piece of tape so that it stays centred.
  8. Put the bowl outside in the sun.
  9. Leave it for several hours. Come back periodically to check on what you see happening.
  10. After several hours there should be a significant amount of water in the cup.

Would you have the skills to fashion a Solar Water Purifier if stranded without fresh water?

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Science Behind the Solar Water Purifier

The Solar Water Purifier uses principles from the water cycle to procure fresh water from salty water or from a source of water which may or may not be palatable due to high mineral or other chemical impurities. Note: boiling water is the only sure way to kill pathogens like bacteria and viruses.

The Solar Water Purifier works as follows:

  1. Sitting out in the sun, the water in the bowl is heated and evaporation of water occurs. The minerals and contaminants do not evaporate with the water and return to their form prior to being dissolved in the water.
  2. When the water vapour hits the plastic wrap, it condenses back into liquid water.
  3. As the plastic wrap is angled towards the small cup, the drops of condensation roll towards the centre and drop into the cup when enough drops have accumulated at that point.
  4. This process will take several hours to produce enough water to quench your thirst and stave off death by dehydration.

Use the Salt Water Circuit outlined in another of my hub's to test the purity of the water. Dissolved salts and minerals create positive and negative ions which conduct electricity. The salt water circuit will determine if there are these ions present and; thus, if your solar water purifier has worked!

In this solar water purifier, the condensation is visible and is caused when evaporated water strikes the plastic wrap and condenses back into liquid water.  It travels down along the wrap to the weight and drops into the small glass.
In this solar water purifier, the condensation is visible and is caused when evaporated water strikes the plastic wrap and condenses back into liquid water. It travels down along the wrap to the weight and drops into the small glass. | Source

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Comments 11 comments

Larry Fields profile image

Larry Fields 4 years ago from Northern California

Hi Teresa. What a cool technique! I have two stooopid questions. First, do you really need the salt?

Second, couldn't the technique be adapted for the small-scale, personal-use production of Appalachian-style 'moonshine'?

Voted up and interesting.


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Larry, you don't really need the salt but using the salt demonstrates that salt water can be purified by testing the distillate. Any water can have the salt and mineral ions removed using this process but as a science experiment adding the salt gives measurable results. As for the production of moonshine, he, he, I'm not too familiar with that process but I guess distillation is distillation! Thanks for the interesting comments Larry, you've given me something to ponder.


RedElf profile image

RedElf 4 years ago from Canada

Fascinating article! I have seen similar water collectors that will work in the desert using rocks, fire, and a tarp. Love science!


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Thanks RedElf. Science with readily found objects is fun. Thanks for stopping by to read!


thumbappoo profile image

thumbappoo 4 years ago from Kerala, India

Brilliant. Can be used as a teaching aid in schools.


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

thumbappoo, my thoughts exactly. Glad you stopped by and thanks for leaving a comment.


Nettlemere profile image

Nettlemere 4 years ago from Burnley, Lancashire, UK

I love watching Ray Mears (UK bush craft expert) so I enjoyed reading about this method or water purifying. I like to imagine I'd be prepared for anything in a lost in the wilderness situation.


KenChase profile image

KenChase 4 years ago from Southwest Florida

Good info for those that missed that lesson in school. I have one comment; what you describe is not a purifier, it is a condensation collector. If the tarp or plastic sheeting is contaminated, catching condensation on it will contaminate your water. If you are at sea, the chances of having a clean tarp that does not have a salt residue on it are slim.


Teresa Coppens profile image

Teresa Coppens 4 years ago from Ontario, Canada Author

Ken,

Although at sea the tarp may not be clean the method does "purify" the water from salt. Drinking salt water will further dehydrate cells and strain the kidneys killing the person stranded at sea. If the water is purified of salt then their chances of survival improve greatly! Thanks so much for your comment!


herp-a-derp 2 years ago

is it BPA free?


Teresa Coppens profile image

Teresa Coppens 2 years ago from Ontario, Canada Author

Depends on the plastic you use!

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