Can I fix my leaking bag?

The answer is "maybe"...

Be sure the bag is tied on properly.  If you have leaks between the stocks and the bag, fix that aspect first.  If you have failures in other places, read on...

For hide bags:

• Serious leakage out the "welt" on the bottom of the bag MAY respond favorably to simple seasoning it.
• Leakage through a "thin" spot in the walls (i.e. in a crease or a "rub" point) may be repaired with some sort of adhesive (see below).
• Holes - I've seen repairs made using two rubber washers - one inside the bag and one outside held in place with a very short bolt.  The jist of the repair was  (from the inside of the bag...) nut, metal washer, rubber washer, bag, rubber washer, metal washer and bolt (head out) through it all.

For synthetic bags:

• Leaks at the "welt"/seam below the blowstick stock are usually due to enzymatic action.  Slathering some sort of adhesive on the area can can work - at least for a while.
• Leaks at the grommets are often due to physical failure in the grommet/material seals.  The adhesive below can repair them.  Use a toothpick to open up anything that is loose, then coat the adhesive on a Q-tip (ear wiper) and get it where it needs to be.  I've had grommets OUT of a Canmore bag and a really messed up Shepherd that now play just fine with this approach. 
• Sometimes the grommets "split" where the collar meets the mounting surface.  I've never had any luck there.
• Pinholes can be "slathered" with adhesive.
• If you've abraded the inside of the bag by mounting a dessicant system, I'd try a little slather of adhesive.

If you need an adhesive:

• My favorite stuff to fix pipe bags is "Clear LIQUID NAILS Adhesive: Small Projects and Repairs." This is a clear water-proof product that can be used as a glue for many applications.  It dries pretty stiff, but it really seals.  Be sure the surface is "dry".
• I've also heard of people using Shoe Goo, but have no experience with it.
• Don't use epoxy as it peels off.