The International Space Station's robot arm moves the Japanese Pressurized Module from the space shuttle Discovery's payload bay to its new home on the station. (NASA TV)

Cosmonaut Oleg Kononenko was a plumber for a day, replacing a pump on the International Space Station's sole toilet on Wednesday, with apparent success.

Kononenko, a member of the three-person crew on the station, replaced the gas-liquid separator pump in the portion of the station's toilet that collects urine, and after a series of three tests, the replacement pump appears to be working, NASA said.

Moscow has given the station crew a "go" to resume normal operation of the toilet system, NASA said.

The broken pump was a small but highly publicized issue on the station for more than a week, one that forced the crew to use the toilet on the Soyuz return capsule, as well as a backup bag collection system.

The pump was a late addition to the cargo hold of the space shuttle Discovery, which arrived on Monday, delivering the main section of the $1 billion US Japanese space lab Kibo.

The newly installed Japanese Pressurized Module will open its doors to the rest of the International Space Station later on Wednesday, allowing astronauts their first opportunity to step inside what is now the station's largest room.

Astronauts from the station and space shuttle Discovery installed the module on Tuesday evening using the station's Canadarm 2 robotic arm.

The Japanese Pressurized Module is a tour-bus sized laboratory 11.3 metres long and weighing more than 14,515 kilograms. It's the second of three parts of Japan's Kibo laboratory to be installed at the station. The first component, essentially a storage closet, was installed in March. The third component, an "outdoor" platform for experiments needing exposure to the environment, is scheduled to arrive in 2009.

Astronauts Mike Fossum and Ron Garan, who performed the first spacewalk of the mission on Tuesday to help install Kibo, will sleep in the station's Quest airlock Wednesday night in advance of their second spacewalk, scheduled for Thursday.