Several things are likely. First off, my bet is the oring is still where it should be. There is an oring groove on part 23. The oring sets fairly deeply in that groove, odds are the oring stayed in place, as it should, so the reason you did not have an air leak is everything is back in place. If it was missing, like the rest have said, you would have known it, no way it would have sealed against HP. The 100psi drop could be anything, including tanks moved from the sun to a shady spot or if you mean they dropped shortly after entering the water, I would expect that much drop and more, the river water is going to be cool. If you SAC rated did increase as much as you say, it had to be nerves, a leak that big would be obvious.
The o-ring is confirmed missing. There was no audible leak, no bubbles visible. The pressue drop was not from moving the tank from the sun to the shade - that did not happen. Nor was it from entering the water. The tanks were not moved.
The leak was not obvious to me or my buddy - who were specifically looking for one - nor to either of the other 3 people we entered the water with.
These are the facts.
Where did a second stage leak enter the conversation?? An IP gauge is not used to test second stages other than verifying they are getting the proper IP.
In post #7, AWAP suggested a 2nd stage leak. An IP guage can be used to determine pressure drop (ie leak) with the regs pressurized and the tank shut off.
---------- Post added August 23rd, 2013 at 04:50 PM ----------
I suspect that the o-ring stayed put inside the reg body or the yoke retainer, and that's why you never saw it. Pull the yoke retainer off again and look for it; you'll find it. Interesting how it says that the yoke retainer is only held in finger tight in your excerpt from the manual. There's got to be another step where it says to torque it to a given spec, isn't there? A yoke retainer should really be tighter than hand tight. That's a classic spot for being manhandled (i.e carrying the tank around by the 1st stage on a boat) and there's a huge pressure gradient on that o-ring.
The o-ring is not in place. I confirmed that before my original posting.
My quick scan of the manual did not give a torque spec forr the retainer, but I have not yet read it closely.
---------- Post added August 24th, 2013 at 03:00 PM ----------
The 1st has had the o-ring replaced, and is tight. I had put it in for service before it occurred to me to leak test it here at home to see where it was escaping.
I just tested the 2nds, and they are tight. I left them pressurized for 30 minutes with the tank valve off, and there was zero pressure drop.
---------- Post added August 24th, 2013 at 04:50 PM ----------
From this thread
http://www.scubaboard.com/forums/regulators/346813-regulator-inspection-checklist-rev-7-a.html
"6.
Check for air leaks by putting regulator on a tank and with the pressure on, first listen to any leaks, then turn the tank valve off but do not purge the reg. Note the SPG pressure and leaving it undisturbed come back in 5 or 10 minutes. The SPG pressure should be close to the original value.
A drop of 200-400 psi is no big deal, but a large drop in pressure indicates something is leaking beyond the normal limits. If the leak is so fast you can see the needle drop just looking at it, the leak is probably large enough to warrant fixing before you dive."
Based on that, it would appear that the pressue drop I experienced was not in fact such a big deal.
At this point I can only surmise that when I snugged the retainer with a wrench, the machined surfaces were sufficient to seal without the o-ring.
