Urine can be purified into drinkable water through distillation, which separates water vapor from dissolved waste. Drinking urine directly is not safe because it contains concentrated salts, urea, and metabolic waste that accelerate dehydration. But with the right method, you can recover clean water from it. The approach depends on your situation: a survival scenario with minimal supplies, or a more controlled setup with access to equipment.
Why You Can’t Just Drink It Straight
Urine typically has an osmolarity (a measure of dissolved particles) above 800 mmol/kg when you’re even mildly dehydrated. That concentration of salts and waste products forces your kidneys to use more water to process it than you gain by drinking it. The result is a net loss of hydration, similar to what happens when you drink seawater. The more dehydrated you are, the more concentrated your urine becomes, making the problem worse with each cycle.
Beyond dehydration, urine contains bacteria that multiply quickly at room temperature. Within hours, bacterial growth can make stored urine a source of infection if consumed. Purification needs to address both the dissolved solids and the microbial contamination.
Solar Still: The Survival Method
A solar still is the simplest way to distill water from urine using nothing but sunlight, a container, plastic wrap, and a collection cup. The sun heats the urine, water evaporates, condenses on the plastic, and drips into a clean vessel. The dissolved salts, urea, and bacteria stay behind in the original container.
To build one, you need a wide bowl or hole in the ground, a smaller collection container placed in the center, and clear plastic stretched tightly over the top. Place a small rock or weight on the plastic directly above the collection container so it forms a low point. Condensation will roll down the underside of the plastic and drip into the cup. Seal the edges as tightly as possible to trap moisture.
The yield is low. Research testing small-scale solar stills found that real urine produced about 10% water recovery over six hours of direct sunlight, meaning 125 mL of urine yielded roughly 12.5 mL of distillate. Urine that had been sitting longer (partially broken down by bacteria) recovered slightly more, around 15%, likely because chemical changes made the water evaporate more readily. Maximum recovery in lab conditions topped out at about 17%. That means you’d need a large surface area and a full day of strong sun to collect enough water to matter. In a true survival scenario, a solar still works best as a supplement alongside other water sources, not a primary supply.
Heat Distillation With a Fire
If you have access to fire and basic containers, heat distillation is faster and more efficient than a solar still. The principle is the same: boil the urine, capture the steam, and condense it back into liquid water.
You need two containers and some way to connect them, even a simple tube or angled surface. Pour the urine into a pot and cover it, directing the steam through a tube or along a tilted surface into a second, cooler container. The steam is pure water vapor, leaving salts and waste behind. If you don’t have tubing, you can improvise by placing a cooler lid (like a metal plate) at an angle over the boiling pot, letting condensation run off the edge into a collection cup.
Heat distillation recovers a much higher percentage of water than solar methods because you’re pushing the temperature well past what sunlight alone achieves. You can realistically recover 50% or more of the original volume, depending on how long you keep the heat going and how efficiently you capture the steam.
How NASA Purifies Urine in Space
On the International Space Station, astronauts drink recycled urine daily. The ISS urine processor uses a vacuum-assisted evaporation and condensation system that recovers 74 to 85% of the water. The low-pressure environment inside the machine lowers water’s boiling point, reducing energy needs.
Even this advanced system has problems. Mineral buildup and bacterial contamination inside the equipment require regular maintenance. For longer missions, engineers have tested a five-stage treatment process that includes crystallization to remove minerals, biological treatment to break down organic compounds, and finally nanofiltration and reverse osmosis to strip out any remaining contaminants. The result is water that meets drinking standards.
You won’t replicate this at home, but it illustrates an important point: distillation alone handles the bulk of purification. The additional stages exist to deal with trace organic compounds and to keep the equipment running over months and years.
Recovering Urea for Fertilizer
Some people searching for urine purification are interested in extracting useful compounds rather than drinking water. Urea, the nitrogen-rich compound that makes up most of urine’s solid content, is a valuable fertilizer.
The simplest extraction method involves evaporating all the water from urine to collect the dried solids. The resulting powder is about 41 to 43% urea by weight, with the rest being various salts and organic compounds. To increase purity, researchers have developed a recrystallization process: the dried solids are dissolved in ethanol, which dissolves urea much more readily than the impurities. When the ethanol evaporates, relatively pure urea crystals form. This process raised urea purity from 43% to 76% when using real human urine, with a yield of about 67% of the total urea present.
One important step: treating the urine with calcium hydroxide before drying prevents bacteria from breaking urea down into ammonia, which would otherwise cause significant nitrogen loss and a strong smell. This stabilization step is essential if you’re storing urine before processing it.
What Actually Makes the Water Safe
Distillation, whether solar or heat-based, handles the two main dangers in urine: dissolved solids and pathogens. Water vapor leaves behind salts, urea, creatinine, and other waste products. Bacteria and viruses cannot travel in steam, so properly collected condensate is microbiologically clean.
The distillate may still contain volatile organic compounds, small molecules that evaporate along with the water. These are present in trace amounts and pose minimal short-term risk, but they’re the reason NASA adds extra filtration stages for long-term use. For emergency or short-term situations, simple distillation produces water that is far safer than drinking urine directly.
If you’re using a solar still in a survival situation, make sure the collection container is clean and that the plastic wrap doesn’t sag into the urine itself. Any splash contamination defeats the purpose. Replace the urine in the still periodically, since the remaining liquid becomes increasingly concentrated and eventually stops evaporating efficiently.