WASHINGTON (AFP) - Two US astronauts Monday finished the fourth and last spacewalk of the shuttle Endeavour's mission at the International Space Station, completing all the tasks and repairs required of them, NASA said. The "home improvement" mission at the orbiting station will be extended by one day with the Endeavour's return to Florida set for Sunday, a National Aeronautics and Space Administration spokesman at Johnson Space Center in Houston, Texas. The spacewalkers, Steve Bowen and Shane Kimbrough, closed the hatch of the ISS decompression chamber at 0031 GMT, ending their spacewalk, a commentator said on NASA television. Their EVA " extra vehicular activity, NASA talk for spacewalk " lasted six hours, seven minutes, 23 minutes longer than programmed. The two astronauts finished cleaning, lubricating and replacing eleven of twelve ball bearings of a rotation device on one of the ISS's three double solar antenna arrays, or Solar Alpha Rotary Joint, which was stuck. The space repair began during the first spacewalk a week ago, and on Tuesday the joint will be tested to see if it works properly. The astronauts also installed a camera on one of the ISS's truss segments and a Global Positioning System on the Japanese Kibo laboratory module. The four spacewalks brings to 118 the total EVAs " 745 hours, 29 minutes " used in building the ISS since it was first placed in orbit on Nov 20, 1998. The orbiting structure is scheduled to be completed by mid-2010. NASA decided to extend the Endeavour mission by 24 hours to 16 days, to give the astronauts time to fix a faulty urine processor unit they delivered that is designed to process urine, perspiration and bath water into drinkable water. The problem a centrifuge motor inside the distillation unit that was running too slow and drawing too much electrical current has apparently been found and the 250 million dollar machine should produce samples to be analyzed back on earth, NASA said. The device is essential for doubling the accommodation capacity, as it would be able to recycle the station's 6.8 tonnes of waste water produced each year. Once in place, the unit would make it no longer necessary to regularly ferry vast quantities of water to the space station. Endeavour is set to undock from the ISS Friday morning, with landing at the Kennedy Space Center in Cape Canaveral, Florida, at around 1:18pm (1818 GMT) Sunday. Endeavour has delivered 14.5 tons of equipment to double the ISS' crew capacity from three to six. Besides the urine-recycling unit, the astronauts installed a freezer and an oven for scientific experiments by NASA's Destiny Laboratory Module, two new sleeping quarters, exercise equipment, a second toilet, and two new ovens and a refrigerator for food preparation.