#explainer
The ISS combines supplies delivered from Earth with recycling. Water is also recovered by treating condensed humidity and processing urine. Oxygen generators use electrolysis: electrical energy splits water into oxygen and hydrogen.
Wastewater does not go straight into a drinking pouch
Water passes through multiple treatment stages and quality checks. Urine processing is only part of the chain; more water comes from moisture exhaled by the crew. The system reduces dependence on cargo deliveries but does not eliminate every loss.
Oxygen is not enough
A habitable atmosphere also requires carbon-dioxide removal, suitable pressure and air circulation. Stored supplies and backup methods provide oxygen as well. Recycling is therefore part of a broader life-support system, not one device that closes the entire cycle without additional supplies.
Is recycled water different from water on Earth?
The resulting quality matters, not where the molecules came from. Water on Earth also repeatedly passes through natural and engineered cycles. On the station, treatment is part of a closely monitored system with limited supplies and spares. Unacceptable water is reprocessed; the phrase drinking urine omits this essential purification step.
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Key points
- Water passes through multiple treatment stages and quality checks.
- A habitable atmosphere also requires carbon-dioxide removal, suitable pressure and air circulation.
- The resulting quality matters, not where the molecules came from.
Sources & further reading
- Oxygen generation, water treatment and ISS atmosphere control.
- Station operations, logistics and crew exercise.
- Daily life, hygiene and work aboard the station.
- Sleeping bags and sleeping conditions in microgravity.
- Hygiene systems, ventilation and spacecraft habitability.
Spaceflightpedia. (n.d.). Where do ISS astronauts get oxygen and water?. Retrieved 17 October 2026, from https://spaceflightpedia.com/article/iss-oxygen-water
article text — CC-BY-SA · ◉ NASA photography — public domain · ✦ AI illustration — marked, generated from sources
More questions on this topic
- How does the ISS work?
- How do astronauts use the toilet in space?
- How do astronauts sleep in space?
- What happens if the ISS loses pressure?
