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Can You Drink Boiled Sea Water? 3 Methods for Desalination

Can You Drink Boiled Sea Water? 3 Methods for Desalination

Per the well-known poem by Coleridge, there may be plenty of water available, but if proper precautions are not taken, it cannot be safely consumed.

Some assume that simply boiling seawater will make it safe for human consumption, but is there any truth to this?

Can you drink ocean water if you boil it? No. Boiling seawater leaves behind a higher concentration of salt, making it even less potable. Boiled ocean water is somewhat decontaminated due to removing bacteria and pathogens, but it can only be drinkable when the salt is removed via distillation or reverse osmosis.

With increased global pressure to provide fresh water to those in dire need, the removal of salt or “desalination” of seawater is becoming a highly sought-after process.

There are three main methods of this, which we’ll discuss below alongside common queries surrounding the safety of boiled ocean water.

Why Boiling Sea Water Doesn’t Make It Safe To Drink

Boiling seawater removes some harmful substances, but it does not remove the salt from the water, which is the key to making ocean water potable.

Let’s look at the health impact of drinking seawater, its salt levels, and what boiling it actually achieves.

What Happens if You Drink Sea Water?

Sea water is four times saltier than our blood, containing a concentration of 35 grams per liter compared with our blood’s salinity of just 9 grams per liter.

According to assistant clinical professor Dr. Christanne Coffey from the University of California, “this huge increase takes the water needed inside our cells to our bloodstream, affecting brain functioning and hastening death.”

Our kidneys also work overtime to make us urinate more, making us dangerously dehydrated.

Another danger, according to Manisha Juthani, MD, a specialist in infectious disease, is that “certain germs can survive in ocean water and cause infection when pathogens are swallowed, such as E.coli.”

Salinity of Ocean Water

Seawater salinity lies in the range of 33 to 37 grams of salt per liter, averaging out at 35 grams of the dissolved salts (sodium and chloride).

Factors Affecting Salinity of Ocean Water

Sea water becomes salty in two main ways. The first is due to slightly acidic rain eroding rocks that then break down, carrying salts and minerals into streams and rivers, which eventually end up in ocean water.

The second factor in seawater salinity is the vents in the seafloor that send up hydrothermal fluids.

As the magma from the Earth’s core heats the surrounding water, iron, copper, and zinc are carried with it, according to the National Ocean Service.

Salinity then varies across the world’s ocean basins due to levels of rainfall and water evaporation.

Ocean water in the tropics, for example, receives consistent rain that brings freshwater to the ocean, helping to decrease the salinity. 

Comparatively, the water in the Red Sea and the Persian Gulf region has extremely high salinity (around 40%) due to little freshwater inflow and high evaporation, caused when freshwater travels as water vapor from the ocean surface to the atmosphere.

What Does Boiling Water Remove?

Boiling seawater removes bacteria and pathogens but not chlorine (salt) or lead.

When heated to 158°F, 99.999% of bacteria, protozoa, pathogens, and viruses will be removed from water in under a minute, according to the World Health Organization.

However, even when fully boiled (at 212°F), seawater will not be drinkable.

Does Boiling Water Remove Salt?

No. Boiling water won’t remove salt from ocean water. In fact, the process will actually increase the sodium content!

When salty water is boiled, the water in the vessel begins to evaporate, reducing the volume of water and leaving the salt behind. Unless this water vapor is collected and removed, boiled seawater remains salty.

Does Boiling Water Purify It?

No, boiling water does not purify it. Boiling water simply removes bacteria and cannot remove other contaminants such as lead and other trace metals.

A water purification system is required to fully purify water.

Does Boiling Water Remove Chemicals?

Only distillation systems can remove chemicals from drinking water. Boiling alone will not rid the water of chlorine and other chemical contaminants.

According to Kwaku Amin, pharmacist and curator behind the blog Air & Water Expert, boiling water can remove “free chlorine” but not chlorine that has been combined with other chemicals. 

Free chlorine is essentially the amount available to eliminate microbes and neutralize contaminants in water but has not yet bound itself to other chemicals in the water.

So, this free-floating chlorine will be removed during boiling but not the total amount of chlorine in the water itself.

Desalination of Ocean Water

Desalination processes such as reverse osmosis make it possible for the salt to be removed from seawater by separating the vapor from the solid solvent.

Unlike boiling water, this type of high-pressure system can actually remove chemical contaminants such as:

  • Sodium
  • Chloride
  • Lead
  • Chromium
  • Copper
  • Metal ions
  • Aqueous salts

This is in addition to reducing traces of fluoride, radium, arsenic, and many more nutrient contaminants.

Small waves rolling to shore against a pretty blue sky.

How To Make Ocean Water Drinkable

The only way to achieve safe drinking water from the ocean is to pull the salt from the water via desalination, which is unfortunately not yet sustainable on a mass scale due to expense and energy use.

Method #1 – Thermal Distillation

This process converts saline water into vapor. A specific amount of heat is provided to get the water boiling, and because salts have a higher boiling point than water, these remain in the desalination chamber.

Meanwhile, the resulting evaporated water is collected and condensed, forming high-purity distilled water.

Because this ultra-pure water contains none of the natural electrolytes that are vital to health, small amounts of chlorine and pH treatments are then added to the water to make it potable.

Method #2 – Solar Distillation

Solar water distillation uses the sun’s energy to separate salt from freshwater. This is typically done by filling black-bottomed vessels with seawater and leaving the top of the glass or plastic vessel clear.

As the untreated seawater absorbs the sun’s heat in the blacked-out portion, it reaches a high enough temperature to evaporate, which becomes trapped by the clear top where it can be funneled away as a vapor to cool and condense back into potable water.

DIY Solar Distillation

Because solar distillation or “solar stills” are low in cost and low maintenance, they can even be set up in your backyard quite easily by digging a 3 x 3 foot pit, filling a plastic bottle with seawater, and burying the bottle halfway into the center of the hole before covering the pit in black sheeting. 

You can get an idea of how it’s made below.

Method #3 – Reverse Osmosis

Simply put, osmosis is when solvent molecules pass through a semi-permeable membrane from a low-concentration solution to a higher-concentration solution.

So reverse osmosis works by applying roughly 50-60 bars of pressure upon salt molecules, forcing them to pass from the high-concentrate solution (via a membrane) to the low-concentrate side – so filtered water remains on one side and salt on the other!

Reverse osmosis is currently used in the world’s largest power plants and much smaller operations (like these portable water filters used on camping trips).

Related Questions:

How Long Can You Survive Drinking Sea Water?

You will only survive less than a week if living on seawater alone, though the biologist Alain Bombard survived 65 days on a careful supplementary regimen.

Because seawater increases the salinity of your blood, the kidneys must work harder to expel the excess salt, using more water and leaving you thirstier and even more dehydrated.

Does Boiling Water Kill Everything?

No, boiling water does not kill everything. At the most, boiling water will kill or inactivate bacteria, viruses, and other pathogens by disrupting their essential proteins and structures, but it won’t remove chlorine or lead traces.

According to the NY State Dept. of Health, boiling is more akin to “pasteurization than sterilization.”


To sum up, boiling ocean water will remove some impurities, but it simply isn’t enough to make it drinkable.

Removing the salt from saltwater is the key takeaway here as it’s this element that poses the greatest danger to our health.

Certain methods make it possible to remove salt from ocean water and make it drinkable, but we’ve still a long way to go before desalination becomes an affordable and sustainable widespread practice.