Space Bags are storage bags that are designed to fit clothing and other compressible items. A vacuum hose attached to a valve connected to a filled bag sucks out all the air, crunching down the bag's contents and sealing them once the air is removed. The bags are useful because they can dramatically save space when storing items or when packing them for a trip. However, the bags can tear, and once they do, the seal is lost and air can get back into the bag. Finding these leaks takes diligence.
Fill the bag with several towels and close it. Vacuum the air out through the seal and then close the valve once the air is out. Place your ear close to the bag and listen for the hissing sound of air reentering the bag. Pay particular attention to the area around the seal as well as the bag's seams because leaks are most likely to spring in these areas. If you can't hear anything, reopen the bag to let air in, close it again and push down, listening for the hiss of air escaping through the same leak.
Empty the bag and close it with air still inside. Squeeze the bag gently with one hand while feeling the various areas of it with another. Air that has entered the bag through a leak will come back out through the same space when the bag is compressed. Locate the leak through feel.
Empty the bag's contents and then close it with air inside. Submerge it in a bathtub full of water and squeeze the bag. Air bubbles exiting the bag identify the location of the leak.