The 13 people aboard the crowded International Space Station can breathe a bit easier now that some astronaut plumbers have fixed a broken zero gravity toilet.

The toilet is one of two orbital commodes on the space station for the outpost's permanent six-person crew and seven visiting astronauts from the docked shuttle Endeavour.

It flooded on Sunday, forcing Mission Control to ask the shuttle and station crew to hang an "out of service" sign on the door until further notice.

Space station crewmembers repaired the Russian-built space commode by replacing a separator pump and control panel.

The fix took them much of Monday morning to perform, but in the end Mission Control declared the revived space bathroom — known as the Waste Hygiene Compartment, or WHC — fit for astronaut use.

"Copy, the WHC is go for nominal ops," Canadian astronaut Robert Thirsk replied.

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The call was good news for the space station, which is currently hosting its largest crowd ever. It means astronauts won't have to resort to Apollo-era bags to stow their waste once the commode aboard Endeavour was full.

By coincidence, Thirsk repaired the space toilet on the 40th anniversary of the Apollo 11 moon landing on July 20, 1969. Two astronauts were also working outside the station to deliver spare parts in the second of five spacewalks by Endeavour's crew.

Space toilet breaks

At the start of Endeavour's mission, NASA wanted astronauts to refrain from using the shuttle's toilet while docked at the station because the vent valve used to dispose waste water overboard is located too close to a new experiment porch, which spacewalkers installed on Saturday.

When the toilet broke, Mission Control gave the okay to use Endeavour's bathroom temporarily, while drawing plans for a repair.

NASA spokesperson Brandi Dean said the bathroom was fixed before the wastewater tank aboard Endeavour was full, so no overboard dump will be required.

"Thanks for the help," Mission Control told Thirsk.

The $19 million space toilet is the newer of two bathrooms aboard the International Space Station and is installed in NASA's Destiny laboratory.

It was delivered last fall and joined an older space toilet, also a Russian design, which is located in the station's Russian-built Zvezda service module.

Since astronauts are weightless in space, the space toilets use airflow and vacuums to draw waste away from the body in place of gravity.

The newer toilet is part of a larger wastewater system that recycles astronaut urine, sweat and wastewater back into drinkable water.

The older toilet has failed in the past as well, but was successfully repaired last summer. NASA officials have said that two functioning toilets are a vital requirement for supporting permanent six-person crews that can temporarily peak at 13 people during shuttle missions.

The space station doubled its crew from three to six people for the first time in May.

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