Here's how astronauts use toilets in zero gravity. Samantha Cristoforetti, an Italian astronaut told how astronauts urinate in zero gravity. Cristoforetti said that it is not easy to do so and it could be considered as a challenge.

Astronauts enter the rubber hose, which uses suction to collect urine in order that it doesn't spread in the surrounding space. Afterwards, everything is moved to the urine processing assembly (UPA), where it is recycled into drinkable water.

It is important to keep surroundings clean and when onboard, water supplies are not sufficient and urine is utilized by converting it into drinking water.

The urine processing makes use of a low pressure vacuum distillation process, which utilizes a centrifuge to balance for the zero gravity and therefore helps separate liquids and gases.

A load of 9 kg/day could be handled in the process. Approximately 70% of the urine's water content can be recycled to make it potable. Water is tested by the onboard sensors and unwanted water, which is not drinkable, is returned for refiltering. It is difficult to do so many things in space, so it's really great on Earth, where things are much comfortable.