(This reply was in response to Rob_E. For some reason, the part that I quoted did not carry over.)

I'm fairly sure that you can. I'm no expert, but from what I've read, Nikwax restores waterproofness to fabrics. I got a bottle of the pre-wash & a bottle of the spray on cleaner for about $25 total. There's enough in there for probably two rain jackets.

The prewash may not be completely necessary, but for as inexpensive as it was, I figured it would be worth it. One other note, if you do buy the Nikwax waterproofer (I forget the actual name) they sell two application styles, one that you put in the washer & wash into your clothes & another that you spray on. I was going to buy the washer one (as it's simpler) but I read online that it's better to get the spray, as the wash-in style will coat your entire garment, and you really only want the spray on the outside.

I don't have any financial (or other) interest in the company, but I have been pleased with the results I've seen from their products.