A whopping 70% of Earth’s surface is covered by water, but most of this is saline ocean water, which is non-potable and thus unsuitable for human consumption.
Yet, this doesn’t mean we can’t tap into this resource; quite the contrary! And this is what we’re going to talk about today: all the methods on hand for purifying salty water and turning it from something harmful into something we can drink.
So let’s jump right into it and see how to an water into refreshing, life-saving drinkable water.
You should never drink saline water
Before I dive into the nitty-gritty of desalination, let’s put things into perspective on why you should prepare and learn this not so common skill.
Nations worldwide are facing critical fresh water shortages. Ironically, some countries are surrounded by ocean waters, yet their citizens have no water.
Although technological advancements have enabled us to convert dirty water into drinkable water, these techniques often fall short when it comes to removing salt from the said water.
Hence, inventive minds have been hard at work, devising ways to convert ocean water into potable water on a large scale. One such method is desalination.
However, just as a quick heads up, guzzling saltwater straight from the ocean is never a good idea. With an average salinity of 35,000 PPM, it’s drastically above the suggested 50 PPM for human consumption. Drinking saltwater would only accelerate dehydration.
Now, imagine you find yourself stranded near the coastline or out in the open sea, with no fresh drinking water within reach. The only viable option would be to purify the ocean water yourself. Let’s learn how to do it.
Survivalist Toolkit: Making Salty Water Drinkable
I will highlight two primary methods for desalination: solar thermal and thermal distillation by fire.
Both techniques hinge on evaporating the water, leaving behind the salt and impurities, and then collecting the clean vapor, which is then turned into safe to drink, regular water.
If you’re interested to know more around this topic, you can check out may previous article answering an important question: Does boiling water purify it?
Solar Desalination by Distillation
A common method to generate fresh water from salty seawater is solar distillation. It’s a mobile and sustainable approach requiring nothing more than the sun’s heat to distill the water.
It might take a bit longer than other methods, but the simplicity and minimal effort needed to set it up make it a perfect option when you are in need.
You do need some minor equipment to pull it through, but as you can see below, the requirements are not massive.
Solar Still: Plastic Bottle Design
This method doesn’t boil the water but slowly evaporates it using the sun’s heat. It will take longer than boiling, but setting up multiple stills can secure enough drinkable water to keep you alive.
This works specifically well in hot climates – for example, if you’re stranded on a deserted island with the tropical sun blazing overhead. Let’s see what you need to make drinking water using the solar still method.
What You’ll Need:
- One large plastic container (like a 1-gallon milk jug or a 2-liter soda bottle with a lid)
- A smaller plastic container that fits inside the larger one (like a water bottle or a 20oz soda bottle)
- A cutting tool (a knife, a sharp stone, or even a torn soda can)
Steps to Build the Solar Still for Purifying Water
- Cut the bottom off the larger plastic bottle, then fold it under and inwards to create a trough to catch condensation.
- Cut the top off the smaller plastic bottle to serve as the holding vessel for the saltwater.
- Place the filled holding vessel in a spot with direct sunlight.
- Cover the holding vessel with the larger catch vessel, ensuring a tight seal.
- Place the still in the sunlight and wait for several hours.
Water will evaporate from the small bottle, it will hit the walls of the larger container and then, through condensation, it will turn back into safe to drink water.
After setting up the stills, find shade and rest. After a few hours of sun exposure, you should have fresh drinking water in your catch vessels.
Remember, in survival scenarios, any hydration is a lifeline, but don’t expect this method to produce tons of water – unless you have plenty of stills set up or very large containers.
Ideally, you’ll complement this method with other passive collection methods like wrapping a plastic bag over foliage to collect condensation.
The ‘Hole in the Ground’ Solar Distillation Technique
This method requires fewer materials than above, although it’s not an ideal situation. But we’re talking about survival here and anything can help.
This method essentially mimics the natural water cycle but on a much smaller scale. Sunlight warms the saltwater in a hole, creating vapor, which then condenses on a plastic sheet above and drips down into your catch vessel as pure water.
Gear You’ll Need:
- Digging tool (spoon, stick, piece of glass, aluminum can)
- Non-absorbent cover material (clear plastic, tarp, waterproof cloth, sheet of metal, plywood, pane of glass)
- Freshwater catch vessel (aluminum, plastic, wood, or stone container)
- Small rock to weight down your condensation catch surface
Steps to Follow:
- Choose a spot that gets maximum sunlight.
- Dig a hole using your selected digging tool.
- Pour saltwater into the hole until it’s one-fourth full, and place your catch vessel in the center. You might need to weight it down with a small rock.
- Cover the hole with your non-absorbent material, securing the edges with dirt or heavy objects like rocks.
- Place a small weight, like a rock, at the center of your cover material to create a low point over the mouth of your catch vessel – this is where the evaporated water, through condensation, will start dripping into your catch vessel.
Here is a video showing you this method in action:
Fire-Based Thermal Distillation
If you’re lucky enough to have fire-friendly weather and abundant fuel, boiling saltwater is a foolproof way to get freshwater. It’s also a lot faster than the methods recommended above.
Once you bring the water to a boil, it produces steam. As this steam cools and condenses, it transforms into droplets of water that you can collect. Here is how to do it.
- Fire ignition source (lighter, match, grill starter, flint stone)
- Fire fuels (wood, brush, trash)
- Non-flammable saltwater holding vessel (large metal or tin)
- Freshwater holding vessel (metal, tin, steel, or plastic)
- Prepare a fire in a suitable spot.
- Position your saltwater vessel above the flames using stacked fuel.
- Once the fire burns down to solid glowing embers, place the catch surface diagonally above the boiling water, ensuring one corner is lower than the rest to facilitate drip collection.
- Position your freshwater vessel under the lowest corner of the catch surface, so that water drips into it.
This method brings back a nostalgic memory of my early survivalist days when all I had was a fire, some stones, and a thirst for fresh water.
Of course, I wasn’t in a real emergency – just preparing. But you never know when this could come in handy.
This method of making safe drinking water out of saline water involves heating stones in a fire and then transferring them into a water-filled vessel. The heat from the stones creates steam that you can collect and condense into freshwater.
Important Precautions to Take
Some stones can explode when heated due to trapped moisture within, causing a potential hazard. Stay clear of stones like shale, slate, and quartz.
- Non-flammable container for holding saltwater.
- Freshwater catch container.
- Fire fuels.
- Metal pot with a lid (ideal but not mandatory).
- Freshwater collecting vessel (metal, stone, or plastic).
- Fire ignition source.
- Suitable stones for water boiling.
- Non-flammable surface (sheet of metal, wet plywood wood).
- T-shirt, cloth, or thick foliage (for handling hot stones).
- Ignite your fire.
- Let the fire burn down to solid glowing embers, with the rocks of choice in the fire
- When the stones are hot, move them into the prepared container with salty water.
- Put your catch surface at a diagonal over the boiling water, angling one corner lower than the rest.
- Place your catch container under the lowest corner of your catch surface.
- Adjust the placement of your catch container as per the condensation drip.
Summing It Up
Freshwater is as essential to an outdoor adventurer as a compass or a Swiss Army knife. Whether you find yourself on a sunny beach with a plastic sheet or in the woods with a fire and some stones, these methods can help you transform ocean water into lifesaving freshwater.
The amount of freshwater you collect, and the wait time, depends on your situation and adaptability. And if you’re curious, you can read about how long it takes to digest water.
It might seem like a daunting task to gather a gallon of water a day, but with a solid understanding of desalination and enough materials, you can maximize your freshwater collection and survive, which is the most important.
And if you’re not dealing with saline water, you can read my previous article on how to DIY a water filter for survival.
Feel free to share your own desalination stories. Every drop counts, every story matters.
Daniel 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.