I've been working on my newborn CD stash for awhile now. I've bought new, on sale, used on craigslist and a few at a LLL yard sale. These AIO's came from a yard sale. I paid $3 each! I checked out the velcro before buying, because you know that is the first thing to go on a BG diaper, and they both looked in perfect condition. I never thought about the elastic till I got them home and realized that it wash SHOT!!! Now I know why I got such a good deal on them.
I found this tutorial on diaperswappers but can't seem to find the link now.
These are both size Small AIO BG's. The diaper on the right has had the elastic replaced. You can tell the difference is amazing!
Start by cutting a small slit in the end of the elastic casing. Make sure NOT to cut through the elastic or the outer shell. Do the same on the other end. Pull the elastic out of one end.
Cut the old elastic leaving around 3/4in attached to the diaper. Using 100% poly thread, stitch one end of the new elastic to the old still attached piece. Stitch the other end of the new elastic to the old piece that is still in the casing. Pull the old elastic from the other end and pull the new elastic through the casing.
Now you have your new elastic attached to one end and attached to the old elastic on the other and it is in place in the casing. Cut the old elastic off of the new elastic and cut it completely off of the diaper leaving 3/4in like before. Here is where you need to look at the length of the elastic. I had a few replacement kits from Cotton Babies so my elastic only needed to be cut a little to make it the right size for these Small diapers. If you are doing a One Size you will need to leave it a bit longer. Try comparing it to another diaper of the same size.
Once you are happy with the length of the elastic sew the end to the remaining old elastic. Use a whip stitch to close up the slits. All done!! I now have 2 like new AIO's for around $8!! Good luck on yours and if you have any questions please ask.