The Russian-built toilet has been acting up for the past week. A NASA employee is en route to Florida from Russia with a pump and related hardware.
Discovery blasts off Saturday, and forecasters put the odds of good launch weather at 80 percent. The flight is scheduled to last 14 days.
To make room for the pump inside Discovery's crammed cabin, NASA is pulling out several other items. An official says "clearly, having a working toilet is a priority," so some things that aren't needed for the next six months or so can wait.
Discovery's cargo bay is loaded with Japan's Kibo lab that's as big as a school bus.
