NASA astronauts drinking pouches of recycled water, which often includes the urine of their Russian companions. (NASA)

The International Space Station is a stunning triumph of collaboration between the United States and Russia. But physically, the ISS is divided -- there's a U.S. side and a Russian one. And the divide extends to more than just their living quarters and labs: When it comes to recycling water, the two space programs strongly disagree.

Which is why American astronauts drink recycled urine and Russian cosmonauts refrain.

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Both sides of the space station collect water out of the air -- called condensate -- which comes from the breath and sweat of those on board. But they use different processes to treat that water before drinking it, and NASA is a lot less squeamish about throwing urine into the mix -- including any that the Russians have to spare. 

"We collect it in bags, and then the crew hauls it over to the U.S. side,” Layne Carter, who manages the ISS water system for NASA, told Bloomberg. “We don’t do 100 percent of the Russian urine. It depends on our time availability.”

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“It tastes like bottled water,” Carter said "as long as you can psychologically get past the point that it’s recycled urine and condensate that comes out of the air.”

In the future, the U.S. and Russian water treatment systems may become slightly more similar: The U.S. side currently uses iodine to purify water -- which works well, but isn't very efficient, since the iodine has to be filtered out before the water is consumed. The Russian side uses ionized silver (with salts added to improve the taste) which doesn't need to be filtered.

But drinking recycled pee is likely to remain an American tradition. There's even talk of improving the system to make a long-term mission to Mars more viable -- and to provide clean drinking water for those in need of it on Earth.

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