Just finished a North Florida cave diving trip with Lamar English and Ag. Had a few wet dives with water in scrubber and assumed I was just drooling at the great vis and beauty of Jackson Blue/Hole in the wall or the sight of Lamars super fast prototype scooter, etc but that wasnt the case.
I do a neg test before every dive. My unit passed the test (never held a great vacuum from new) but for some reason I double checked. Listening I could hear a very faint hiss. It was very faint and Ive done dives with bigger hisses (very small pin ***** holes in CLs can sound loud but dont let water in)
Anyway I flipped over the center section and what did I find? A two inch long openning in the welded Counter lung seam. See pic. Now the scary thing is with these plastic lungs when you pull a neg the seam closes together and holds a good vacuum!
Only the faintest hiss gave it away.
So now I do a neg AND a positive before every dive
The lungs were just prototypes for testing...guess they failed the test
Take home message for me is plastic seams may be more prone to catastrophic failure over cloth lungs seams.
Luckily I brought the original ones as back up.