DO IT YOURSELF

How to Purify Salt Water: Improving Your Drinking Sources

Purifying salt water
Daniel Carraway
Written by Daniel Carraway

Worldwide, there are a growing number of people dying each year from dehydration and 70 percent of our planet is water. However, most of that water is in our oceans and contains saline or salt water. This is considered non-potable salt water.

A growing concern in the minds of many across the world is the search for new and more effective fresh water solutions. In this article, we are going to show you how to purify salt water on a personal consumption scale.

With varying degrees of severity, countries all over the world are running out of fresh water and have been for decades. Even some countries are completely surrounded by water and are still dying of thirst.

There are now inventions that are capable of converting dirty water into potable water, such as certain filter straws. Although these are great products, they are not capable of removing saline or other heavy metals.

Research and experimentation by varying ingenious minds have been working on new ways to convert salt water into potable water on a larger scale. One way to get clean drinking water from ocean water is a process is called desalination. This is the removal of salt and other solids from ocean water; the process will be discussed in further detail later.

Do not Drink the Water

Drinking saltwater is counterproductive, as the salt actually accelerates perspiration and dehydration. Our oceans have a very high salinity level. On average, our oceans have a concentration of at least 35,000 PPM. The ideal salinity for human consumption is suggested to be 50 PPM, so you can see why drinking it is a bad idea.

Drinking saltwater

You may find yourself located near the coastline or stuck out at sea and realize that you have no access to fresh drinking water. You could be left with no choice other than to try to purify the ocean water one way or another.

Once that time comes, you will need to know how to make ocean water drinkable in the most time efficient and energy saving way, plausible for your circumstance. Like in any survival situation, your careful decisions will define your outcome.

If you have had time to research the area beforehand and were smart enough to bring a “bug-out bag”, you can always have the necessary materials to make ocean water drinkable. This can save time and effort that it would normally take to collect the necessary items.

In this article, we approach water purification from the perspective of being stranded. We suggest two primary methods for desalination by distillation. They are solar thermal and thermal distillation. Solar thermal distillation, as the name suggests, relies on the energy from the sun to heat the saltwater over time to a point of evaporation.

Salt water

Thermal distillation by fire relies on boiling the saltwater in order to initiate evaporation. If you can find the materials to set it up, boiling the saltwater with fire is much quicker and can produce more fresh water than solar distillation. However, the process requires more materials and effort to keep the fire going.

Whether you choose to use solar energy or the energy of an open fire, the design, assembly, and placement of your distiller can mean the difference between life or death.

Solar Desalination by Distillation

Solar distillation is one of the more common ways to produce fresh water from heavily salinized water. One of the benefits of solar thermal distillation is the mobility that it allows. If you have a “bug-out bag”, you’ll already have the items that you need to employ this method. First, we will go over how to create a solar still, as it is one of the most effective ways to go about purifying ocean water in an emergency.

Although the wait time required to distill the saltwater via solar still is longer, this method requires no heat source other than the sun itself, and it requires only minimal effort to build. There are numerous combinations of ways to build a solar still. We’ve broken them down into two very basic designs.

Plastic bottle design

This method utilizes the sun’s energy to initiate evaporation in a passive manner. This is considered a low-temperature distillation process.

Solar Desalination by Distillation plastic bottle design

The clear plastic aids in accelerating evaporation because the sun is not actually boiling the water, this design requires a longer wait period. If you can find enough materials, we recommend that you make as many of these as you can, because having only one may not produce enough drinking water for a human to survive.

The items required are as follows:

  • One large plastic container like a one-gallon milk jug or a 2-liter soda bottle with a lid. This will serve as your surface area for the condensation to collect.
  • One smaller plastic container like a water bottle or a 20oz soda bottle that will fit inside the larger plastic vessel and will serve as your holding vessel for the contaminated saltwater.
  • A cutting tool like a knife, sharp stone, or a soda can be torn in half to cut the plastic.

Steps to build and assemble the still are as follows:

  1. Cut the bottom off the larger plastic vessel and then bend the bottom under and in, to create a catch trough for the condensation to gather. This container will be the catch vessel. You can increase production by increasing the size of the vessels. The more water you will be able to catch and process, the greater yield you’ll have.
  2. Cut the top off the smaller plastic bottle. This will be the holding vessel.
  3. Find an area that is in direct sunlight and place the smaller holding vessel down with the cut end facing up.
  4. Fill the holding vessel with saltwater.
  5. Place the larger catch vessel over the holding vessel. Make sure the larger vessel is snug against the ground or the bottom of your boat, in order to make a tight seal.
  6. Place the still in the sunlight.
  7. Find shade and wait several hours.
  8. A variation of this method would be to place the cut plastic bottles directly against the ground or saturated cloth. This would do away with the use of energy it takes to dig a hole in the ground. Inside the plastic container, the water from the saturated surface will evaporate and collect on the sides as condensation.
  9. After you have set up and placed your stills, we recommend finding shade and remaining as inactive as possible so as not to expend more water than you are getting for your efforts. After several hours of sunlight, your catch vessels should have fresh drinking water in them. The yielded amounts will vary, but in a case of survival, any hydration is good hydration.

Ideally, you will combine various other passive collection methods with your still setup such as wrapping a plastic bag over foliage to collect the condensation.

Hole in the ground design

The hole in the ground design is a very simple and scalable way to collect condensation via solar energy.

This is considered a low temperature distillation process.

Items Required are as follows:

  • One digging tool like a spoon, stick, piece of glass, aluminum can, etc.
  • One clear plastic, tarp, tent material, waterproof cloth, sheet of metal, sheet of plywood, pane of glass, etc., and this will be the surface area that will accumulate the condensation. Ideally, you should use materials that are non-absorbent, but that will still collect the condensation and hold it long enough to re-route it into your catch vessel.
  • One aluminum, plastic, wood, or stone container and this will be your fresh water catch vessel.
  • One small rock for weighting the condensation catch surface.

Steps to Setup

  1. Carefully choose a spot to dig your hole. Make sure the area has as much sunlight exposure as possible.
  2. Dig a hole using a spoon, stick, piece of glass, aluminum can, etc.
  3. Fill the hole one fourth with saltwater, then place your catch vessel in the very center of the hole. It might be necessary to put a small rock inside the catch vessel to weight it down and keep it standing.
  4. Wrap a piece of plastic wrap, a clear tarp, or even some clear trash bags fashioned together over the hole.
  5. Secure it level to the ground by covering around the edges with dirt or mud. If necessary, you can place heavy objects like rocks or wood around the edges to hold it down.
  6. Put a small weighted object like a rock or hardened clay ball in the very center of the plastic, the idea being that the weight of the object in the center will make the plastic droop towards the mouth of your collection container. Once the condensation begins to accumulate, gravity will automatically pull the droplets towards the lowest point, and it will eventually begin to drip into your catch vessel.

Thermal Desalination by Distillation

Boiling Method

Boiling water is a very basic but highly effective way to make ocean water drinkable. If the weather is permitting a fire and you can find the materials necessary to build it and keep it going, this method can yield more fresh water per hour than solar desalination.

Boiling Method

The idea is that the heat from the fire will cause the saltwater in the metal vessel to boil. Once the water begins to boil, it releases steam, which collects on the inside surface of the catch vessel. The condensation then runs to the lowest point, which in this case, is the lid handle, where it drips into a freshwater catch vessel.

Items required are as follows:

  • One heat source to ignite the fire, like a cigarette lighter, match, grill starter, or flint stone.
  • Fire Fuels (wood, brush, trash, etc.)
  • One Large non-flammable metal or tin salt-water holding vessel.
  • One metal, tin, steel, or plastic fresh water holding vessel.

Steps to set up are as follows:

  1. Carefully choose a spot for your fire.
  2. Stack your fire fuel into a shape that you can set your saltwater holding vessel on top of.
  3. Using your heat source, light your fire.
  4. Let it burn down to solid glowing embers.
  5. Place your catch surface at a diagonal over your boiling water. Make sure to angle the surface so that one corner is lower than the other three. This will be where your fresh water will drip.
  6. Place your fresh water catch vessel directly under the lowest corner of your catch surface, so that gravity will route the accumulated condensation directly into your catch.
  7. Carefully place your aluminum or metal saltwater vessel onto the hot coals.
  8. Once the saltwater begins to boil, you will see steam rising and eventually accumulating in your fresh water catch vessel.
  9. It may be necessary to adjust the placement of your catch vessel to align with the fresh water drip.

Boiling stones

Another way to produce condensation is to use heated stones to bring the saltwater to a boil. The idea is to heat a number of small stones in an open fire and then place them into a container of water. The heated stones cause steam. The steam catches on a surface, where it cools causing condensation droplets. The droplets accumulate and re-routed via gravity, to a freshwater catch vessel.

Boiling stones

Precautions – The steam can build pressure in the stone and cause it to explode. Try to avoid types of stones like shale, slate, quartz, and other layered stones. If you are not sure what type of stones you have available, you can test them one at a time by placing them into the fire. Back away and wait approximately 15 or 20 minutes to be safe. If the stones are going to explode, they typically do within that 15-20 minute period. After testing the stone, approach your fire with caution.

Items Required are as follows:

  • One non-flammable container for holding the saltwater.
  • One container to transfer the fresh water into.
  • Fire fuels (wood, brush, trash, etc.)
  • If you can find it, a metal pot with a lid because you can simply turn the lid over, and you already have a low point for the condensation to drip from.
  • One aluminum, metal, or stone vessel to collect the freshwater from the condensation. You can use a plastic bottle if necessary.
  • One source of fire ignition.
  • Stones for water boiling. Make sure that they are dry, as wet stones are more likely to explode. Try to find stones sized appropriately to your fire and your saltwater-holding vessel. Be careful when putting stones in the saltwater vessel, as the stones will cause water displacement and could cause the water to overflow.
  • One sheet of metal, wet plywood wood, or other non-flammable surface, to put over the steam, in order to collect and re-route condensation quickly.
  • One T-shirt, cloth, or thick foliage to use as something to grab the hot stones out of the fire.

Steps to set up are as follows:

  1. Using your heat source, start your fire.
  2. Let your fire burn down to solid glowing embers.
  3. Place your catch surface at a diagonal over your boiling water. Make sure to angle the surface so that one corner is lower than the other three. This will be where your fresh water will drip.
  4. Place your fresh water catch vessel directly under the lowest corner of your catch surface, so that gravity will route the accumulated condensation directly into your catch.
  5. Collect as much saltwater as you can fit in a non-flammable or at least fire retardant holding vessel.
  6. Place your saltwater holding vessel onto the hot coals.
  7. Once the saltwater begins to boil, you will see condensation gathering on your catch surface and the re-routing to the lowest corner and into your fresh water catch vessel.
  8. You might need to adjust the placement of your fresh water catch vessel according to where the condensation drip occurs.

Wrap Up

As mentioned above, water is essential to every human on the face of the each. For people that live near saltwater, it is important to know the necessary procedures to obtain freshwater from saltwater. In this article, we discussed a few methods of desalinating saltwater.

Whether it is low temperature solar distillation or high temperature thermal distillation, any combination of the methods and designs in this article will provide fresh drinking water.

Make clean water

How much fresh water you collect and how long you have to wait for it will depend on your decisions and mentality, as well as the conditions you find yourself in. Typically, in warmer climates the average person requires upwards of 1 gallon of fresh water per day.

Although it may seem that collecting a gallon of water per day is far-fetched, with a solid understanding of distillation by desalination, having enough materials to build multiple stills, and assembling them correctly, you have a better chance of obtaining enough water to survive.

Have you ever turned your own ocean water into drinkable water? If so, we would like to hear your stories.

ABOUT THE AUTHOR
Daniel Carraway
Daniel Carraway

Daniel Carraway joined our team last year. He is a gear freak when it comes to hiking, climbing and camping. He went to REI Outdoor School to meet new people and learn best practices. Don’t even try to argue with him about the latest backpack or ice axe, he tried most of them. Daniel’s dream is to climb Mount Everest.

  • Chynna Lambert

    I remember doing this for our 7th-grade science fair project. If you have electricity, a water distiller works great. Doing this is so fun! Most microorganisms that make you sick can be killed with distilling the saltwater (not just boiling) because they can’t survive in higher temperatures. To make the condensation occur faster, cool down the cover while the water boils.

  • Daniel Carraway

    Thanks for the added tip Chynna! This article is really geared to inform and equip outdoor enthusiasts. I hope all the tips and tricks were useful to you – share them with your friends!

  • Patrick Calhoun

    We actually tried this long ago just for the experience and we were surprised the first time we did it because it worked well. The instructions here are clearer to me and I now understand the explanation of the whole process especially with the help of the video. It reminds me that one has to be ready to use survival skills when camping a lot. Also, that bringing enough water that will last for the whole trip is important.

  • Daniel Carraway

    How was the experience? I used to remember when I was a teen, me and my buddies practice for hours “perfecting” the heat method. It was a good exercise for us since the more we improved our skills on purifying salt water, the more confident we became that we can do anything! 🙂
    Thanks for passing by Patrick and for taking the time to comment.

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