July 20 (Bloomberg) -- Astronauts aboard the International Space Station were forced to make an unscheduled repair of one the three toilets servicing the 13 crew members orbiting Earth, the biggest contingent ever in space at one time.

Space Station Commander Gennady Padalka and Flight Engineer Frank De Winne today replaced components of the Waste Hygiene Compartment, which pumps chemicals to separate liquids from solid waste, NASA said on its Web site. After the toilet broke yesterday, astronauts had to use another one on the station or one aboard the visiting space shuttle Endeavour.

Endeavour docked with the ISS July 17 as part of a 16-day mission to deliver parts and install components to the orbiting outpost. The seven members of the Endeavour joined the six astronauts already aboard.

The Waste Hygiene Compartment system was added to the space station’s Destiny Laboratory in November during Endeavour’s previous mission. It worked for about 15 minutes yesterday before failing, said Kylie Clem, a spokeswoman for the National Aeronautics and Space Administration at Johnson Space Center in Houston.

“When they ran that part, there was some sort of failure that allowed that liquid to flood into the system,” she said in a telephone interview today.

The crew was given the go-ahead to use the toilet again at 12:40 p.m. New York time today, NASA said in a statement.

Spacewalk Ends

Separately, astronauts Dave Wolf and Tom Marshburn conducted a nearly seven-hour spacewalk today on the 40th anniversary of the Apollo moonwalk. It was the second of five scheduled during Endeavour’s mission. The pair stowed spare parts on a platform outside the station and installed a television camera, NASA said.

The crew is scheduled to finish assembling the Japanese Kibo research complex by installing a 9,000-pound (4,082- kilogram) “porch” to be used for experiments needing exposure to space. The facility -- its name means “hope” in Japanese -- is the largest space station laboratory.

The astronauts are also delivering spare parts, setting up two systems for attaching cargo and replacing batteries for one of the solar arrays that help power the station.

Endeavour, built to replace Challenger after it exploded following liftoff in 1986, is the newest of NASA’s space shuttles and first flew in 1992. It is named after a ship commanded by British explorer James Cook. The spacecraft is to return to Kennedy on July 27.

To contact the reporter on this story: Ryan Flinn in San Francisco at rflinn@bloomberg.net

Last Updated: July 20, 2009 19:06 EDT