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The above has happened on the small number of cave dives I have done with the CDG. I must admit I found the experience very unnerving as I felt at the time I was on the point of drowning. In my estimation the amount of water was too much to be breathed past or spat out. Fortunately I was near the start of the sump on both occasions and I was able to return to the surface regain some composure and complete the dive.
I was wondering whether the fact I was using a Poseidon Jetstream at the time could have been a contributory factor in the above incident? My local dive shop recommended that I should cover the holes on the outer circular rim of the second stage with tape and also try and align the whole thing facing downwards whilst diving. I don't know whether this is good advice? However, a member of the CDG with numerous years experience has tested the Jetstream and found no problems with water flooding suddenly into it.
I was wondering whether it is something I was doing wrong? I, however, used Apex regulators on my Open Water course and had no problems what so ever. Please note it has been recommended that I use Cyclon regultors which I have now purchased secondhand. After servicing last Feb. one set needs adjusting so might have to fall back on the Jetstream!
Either grit is getting under the exhaust diaphragm or there is a hole in it.
Both will let water in.
The grit is probably unique to the cave diving which is why it seems OK when tested elsewhere.
Try looking under diaphragm immediately after a dive to see if there is grit there.
Not many people use jetstreams for UK cave diving. Try Cyclon as suggested or better still Mantas although they are obsolete now !!
Ah, the Apex Manta, truly an excellent cave-diving second stage, sadly missed. If only Apex would re-start production of that valve, with a good supply of spare parts, and perhaps tuned to match a DS4 first stage; that would be the cave-diving reg that dreams are made of. 🙂
The jetstream is a fine open water reg, however having dismantled and serviced one, there is no way I would use one where there is any risk of silt or such like. It has too many delicate parts inside.
A bit of grit under the diaphragm or a small hole is unlikely to cause the catastrophic flooding you have described. This occurred in my case when I had removed the second stage cover circlip ( on a cyclon ) and did not put anything in place to stop it becoming displaced. It can suddenly slip without warning, and then the second stage floods completely as the diaphragm is effectively not there.
Just a suggestion , but check the circlip is present ( if the Jetstream has one ) ?
Thanks for all the advice.
Tested the Jetstream on Friday in the Porth yr Ogof resurgence pool. Could not get it to flood with tape covering the holes on the outside rim of the second stage but certainly do not know whether this was preventing the problem.
On Sunday, Malcolm lent me his spare Cyclon for cave dive so no problems with kit.
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