HOUSTON, July 19, 2009 -- Houston, we have a problem.

One of the two bathrooms on the International Space Station is broken. Engineers at the Johnson Space Center are working around the clock to troubleshoot the problem, but it could take days to fix.

Astronaut Hal Getzelman radioed up the bad news to the crew on the space station. "When you get a second, if you could put an out-of-service note on the WHC [NASA's term for a toilet] and advise the crew members that station crew members will have to use the Russian toilet and shuttle crew members on the shuttle until further notice."

European Space Agency astronaut Frank De Winne is the guy tasked with putting his plumbing skills to work on short notice. He asked if engineers had an estimate on how long it might take to get the toilet back in operation.

"No, we don't have a good estimate," Getzelman said. "What happened, the pre-treat (chemical), we think, flooded the pump separator and we may have got some fluid where we didn't want it and it'll take us a while to work through a procedure to recover."

There are 13 people on the space station right now – a record. The crew represents the United States, Russia, Canada, Japan, and Europe. NASA has spent years getting ready for a crowd in space – adding additional sleeping quarters, learning how to recycle liquid waste into drinking water, and installing a second bathroom last year.

This mission, dubbed STS 127, is the first real test of those systems. Mission Control sent up a note to the crew on Sunday warning them to not overuse the new bathroom.

3. WHC USAGE TIME CONSTRAINTS With the high usage on WHC we would like to remind you about time constraints for WHC usage. These can be found on 2.301 WHC Cue Card under the block "WHC Time Constraints." - Recommend 6 min interval between use. - Three uses in a row (<6-min interval) requires a 30-min cool down. - Maximum continuous use is 30-min followed by a 20-min cool down.

Translation: If someone uses the bathroom the next person to use it needs to wait six minutes, and if three people in a row use it six minutes apart it needs 30 minutes to recover.

While it is certainly inconvenient for the crew to be down to one bathroom – the Russians have a working bathroom and there is a toilet on Endeavour. Mission Control wants the astronauts to use it as little as possible because they can't dump the waster overboard for fear of contaminating the new addition to the space station.

If all else fails the crew has at its disposal something the astronauts on Apollo 11 carried on their mission 40 years ago: Apollo bags used to collect fecal material.

The Apollo capsules and the lunar modules didn't have bathrooms, so while one of the toilets on the space station is broken, it shows just how far the space program has come in 40 years.

The space station's urine collection unit was out of commission in 2008 when a faulty pump had to be flown up from the Shuttle Discovery.