The O-Ring would have been fantastic if the tech hand't put the bottom bushing on up-side down. It ended up chewing it up. The rebuild manual is very explicit on this point.
You can see where the O-ring extruded over the bushing and there is a quasi-imprint on it. I can see the mold marks.
What was funny is when I pressurized it after the problem first manifest itself, it took a couple seconds before the leak started. Took that long for the o-ring to creep. And the reg slightly hissed when I took it off the bottle, it was holding back a tiny bit of pressure on the HP side.
Creepy IP was a symptom of the problem. I knew it didn't look right when I was struggling with the G-500. I know good IP response when I see it. The needle on the gauge should snap to attention in a military manner. This was more inebriated.
What is ironic is if I hadn't left that bottle on all night with the leaky G-500 by mistake, it likely would have let go during a dive. I carry a 30cu/ft pony with a R-190/MK-2 as a bail-out when diving solo like today but still, this counts as my worst equipment failure.
I have the bench sheet from the shop with the date and the test results pre and post rebuild. Should I let the owner know?
Hell, I want my O-ring back!
PS THIS IS WHY YOU NEED TO PAY ATTENTION WHEN REBUILDING A MK-20/25. IF YOU HALF-ASS IT, IT WILL BITE YOU IN THE ASS!
By the way, the shop is the regional Scubapro training center. They taught my tech course in 1999.
I had this MK-20 rebuilt last year because I was rusty and wanted it bought up to current spec.
I robbed a rebuild kit and replaced the HP O-Ring. It works again, I need to check the IP tomorrow.
Summary: Tech fucked-up a simple rebuild. HP Oring got chewed-up, blew while sitting on bench just before the dive.