Don't know who told you the manifold nuts are left loose by cave divers, but that's 'crap'.....In the past I've had hydro/viz shops; x-thread band hardware nuts/bolts, crack manifolds, x-thread modular valves etc. then insult me w/some pathetic excuse........Now I disassemble doubles, remove the valves on them and single tanks myself......And I make a point of watching them do the hydro/viz.....Then do the reassembly myself....That way I know for sure there's a new 'ring'/burst disc.......You might want to take a close look (w/a magnifying glass) at your manifold and valves.....If they split the nuts, they probably didn't CAREFULLY align the tanks as they were screwing in the manifold and this can cause micro cracks/fractures in the manifold and valves...........The nuts are there for a reason, leaving them loose is NOT one of them !!!!.........