Bit of a strange one that maybe someone can help me out with.

I was running a bit low on on-board diluent so decided to run the dive from a side mount. Off-board came through the gas block/standard swagelock fitting from CCRB.

I dropped into water with the on-board dil open & isloation valve open, also off-board dil (same gas) plugged in and on. No complaints on surface nor on the descent but suddenly at about 47m I hear a nasty noise (some where between an alarm going off and a scream (leaking gas through a small orifice right?)). Buddy signals I have gas comining out of my back (not an out and out free flow but a constant flow of gas). Nothing wrong on my display, isolated on board gas but screaming continues so shut off external tank, screaming stops as does leak.

At 6mm I turned it back on and nothing, at the surface it was the same thing, no leaks.

Please note, when there is no plug in there are no leaks.

F