So I've had my original (large) Neoair for about a year and a half now and have started to notice some air loss during the night - more than what would be expected due to a change in temperature. I've read in more than a few places that people are returning their pads to Cascade Designs because they have a leak, but can't locate it. This is my experience to share in locating the leak, in hopes that others can benefit from it in the name of resource conservation...
While my pad would not be considered "flat" in the morning (after blowing it up fairly tight at bedtime the night before), when I sat up in the morning and put all of my weight right on my rump, I could definitely feel the ground poking back. If I were to top off the pad at that point, I would say that 2 or 3 big breaths would have filled it back up to tight again. So, I wasn't dealing with a bad leak, but it was enough that it concerned me, so when I found time, I decided to go looking for the leak.
I filled the bathtub with about 3-4 inches of water, and blew the pad up as tight as I could get it with my lungs, and pressed the pad down into the tub, folding it like a taco, the unsubmerged ends running perpendicular to the length of the tub. I started with the grey/silver bottom side up, figuring the puncture was likely on the bottom due to a sticker or rock that got through the ground cloth and tent floor bottom. Well, I went through the whole underside of the pad and didn't find any little streams of bubble emanating from the pad. Uh, oh. This could be more difficult than I thought. I flipped the pad over and started working my way over the top yellow/lime side. I went through it quickly and found no obvious bad leaks (to be expected), so I started going over it more slowly.
I dunked the pad about a foot at at time, and while I didn't see anything, I heard a small pinhole leak squealing after I pulled a section out of the water. I went back a foot and held the section underwater longer, kneading and massaging the pad to try and get the leak to open up more, and finally found a small stream up bubbles when I pulled the top fabric away from the hole in opposite directions. If I just held the pad under water, the leak was much slower and less obvious. Found it! I pulled the pad out of the water, dried off the leaky spot and marked it with a pen.
I had one of the $10 Fast & Light patch kits that are intended for these pads (got it as a freebie throw-in with a Moontrail order) and cut a 3/4" square out of one of the 3 large patches provided in the kit. I cleaned the area around the hole with an alcohol cotton ball, and applied the patch. Our NeoAirs came with some small Tear-Aid patches that I haven't yet used, but the material that comes with the Fast & Light patch kit is lighter weight than the Tear-Aid patches. I would think that the recommendations of using the pre-glued Park or Skab brand bicycle tube patches would be a successful one as well, after seeing and using these recommended patches. They are all very similar, just different thicknesses. Stretchiness of the patch is important. You put it on when the pad is deflated, and then it stretches and conforms to the bumps in the exterior when you inflate.
Feeling confident that I had fixed the problem, I blew the pad back up and left it to sit. After about a day and a half, I found that I can get another breath into it... Another slow leak? Not as bad as the first, but I went through the above process again. This one was harder to find, but again I could hear the leak once it was wet, before I could see it. Submerging it helped, but I also tried a squirt bottle with dish soap and water in it, and that really worked well to pinpoint the leak once I knew it was in a certain area, with soap bubbles slowly growing right over the leak. This second one was again on the top of the pad rather than the bottom. Is the bottom material more durable? Makes sense. I wonder a little about if these holes could be caused by pointy feather quills from my down sleeping bag...
So that second leak is now patched and I'll give it another couple of days again to see how the pad does. My advice is to try these above methods before giving up on a pad due to a slow leak. It really wasn't that bad to locate and repair these holes, as long as you have a little patience and quiet to listen carefully.