Boiling saltwater is a common thought in survival scenarios, a natural impulse to use heat to purify an abundant water source like the ocean. While boiling is highly effective for neutralizing biological threats such as bacteria, viruses, and protozoa in fresh water, it does nothing to remove dissolved minerals. The high stakes of seeking drinkable water in an emergency make it vital to understand the fundamental difference between sanitizing water and desalting it. The short answer is that simply boiling salt water will not make it safe to drink, and consuming it can lead to severe health consequences.
Why Boiling Fails to Desalinate
Boiling works as a purification method because water molecules turn into steam, or water vapor, at a temperature of 100 degrees Celsius (212 degrees Fahrenheit) at sea level, leaving behind any non-volatile contaminants. Bacteria, viruses, and protozoa are non-volatile, meaning they do not easily vaporize, and are therefore left behind in the boiling vessel. This is the mechanism that makes boiling a reliable way to make contaminated fresh water biologically safe.
However, salt, which is primarily sodium chloride, is also a non-volatile compound with an extremely high boiling point of 1,413 degrees Celsius (2,575 degrees Fahrenheit). The heat required to boil water is nowhere near the temperature needed to vaporize the salt. Consequently, as the pure water turns to steam and escapes, the salt remains behind in the pot.
This process actually increases the concentration of salt in the remaining liquid. For instance, while seawater generally has a salt concentration of about 3.5%, boiling off half the water would double the salinity of the rest. Even a slight increase in salt concentration raises the boiling point of the water, a phenomenon called boiling point elevation. This means the remaining liquid becomes hotter and saltier the longer it boils, ultimately becoming more dangerous to drink than the original seawater.
Health Risks of Consuming Saline Water
Drinking water with a high salt concentration creates a serious physiological problem for the human body. The kidneys are responsible for regulating the body’s balance of water and sodium, but they can only excrete urine that is less salty than seawater. The salt level in the ocean is significantly higher than what the kidneys can process without drawing on the body’s internal water reserves.
When highly saline water is consumed, the body attempts to dilute the excess sodium in the bloodstream, a condition known as hypernatremia. To achieve this dilution, the body pulls water from its own cells and tissues. This results in paradoxical dehydration, where the act of drinking water paradoxically makes the person more dehydrated.
Symptoms of severe hypernatremia include excessive thirst, confusion, muscle twitching, and even seizures. In a survival situation where dehydration is already a concern, consuming saltwater accelerates fluid loss and places an immense strain on the kidneys. This stress can lead to kidney failure and, in extreme cases, be fatal, as the body cannot maintain the delicate fluid balance required for organ function.
The Proper Method for Purification: Distillation
The only method that uses heat to successfully remove salt and other non-volatile minerals from water is distillation. The core principle of distillation is identical to that of boiling: heating the water until it evaporates into pure steam. The difference is that distillation involves a mechanism to capture and condense that pure steam back into a liquid form in a separate container.
The process involves heating the saltwater in one container, forcing the water to change phase into a gaseous state, leaving all the dissolved solids behind. This water vapor, which is pure H₂O, is then directed into a cooling area where it condenses back into fresh, drinkable water. This condensed water is free from salt, heavy metals, and biological contaminants.
In an emergency, a simple distillation setup can be improvised using common materials. One low-tech method involves placing a pot of saltwater on a heat source, covering it with a lid that is angled to allow the steam to collect and drip, or using a tube to direct the steam into a separate, cool container. Another common technique is the solar still, which uses the sun’s energy, a sheet of plastic, and a collection cup to create a closed, passive distillation system. While these emergency methods may yield only small amounts, they produce water that is safe for consumption, unlike the highly concentrated, dangerous liquid left behind from simple boiling.
Health Risks of Consuming Saline Water
Drinking water with a high salt concentration creates a serious physiological problem for the human body. The kidneys are responsible for regulating the body’s balance of water and sodium, but they can only excrete urine that is less salty than seawater. The salt level in the ocean is significantly higher than what the kidneys can process without drawing on the body’s internal water reserves.
When highly saline water is consumed, the body attempts to dilute the excess sodium in the bloodstream, a condition known as hypernatremia. To achieve this dilution, the body pulls water from its own cells and tissues. This results in paradoxical dehydration, where the act of drinking water paradoxically makes the person more dehydrated.
Symptoms of severe hypernatremia include excessive thirst, confusion, muscle twitching, and even seizures. In a survival situation where dehydration is already a concern, consuming saltwater accelerates fluid loss and places an immense strain on the kidneys. This stress can lead to kidney failure and, in extreme cases, be fatal, as the body cannot maintain the delicate fluid balance required for organ function.
The Proper Method for Purification: Distillation
The only method that uses heat to successfully remove salt and other non-volatile minerals from water is distillation. The core principle of distillation is identical to that of boiling: heating the water until it evaporates into pure steam. The difference is that distillation involves a mechanism to capture and condense that pure steam back into a liquid form in a separate container.
The process involves heating the saltwater in one container, forcing the water to change phase into a gaseous state, leaving all the dissolved solids behind. This water vapor, which is pure H₂O, is then directed into a cooling area where it condenses back into fresh, drinkable water. This condensed water is free from salt, heavy metals, and biological contaminants.
In an emergency, a simple distillation setup can be improvised using common materials. One low-tech method involves placing a pot of saltwater on a heat source, covering it with a lid that is angled to allow the steam to collect and drip, or using a tube to direct the steam into a separate, cool container. Another common technique is the solar still, which uses the sun’s energy, a sheet of plastic, and a collection cup to create a closed, passive distillation system. While these emergency methods may yield only small amounts, they produce water that is safe for consumption, unlike the highly concentrated, dangerous liquid left behind from simple boiling.