Redundant Octos & 2nd Stages Unable to Deliver Air?

[Nemrod]

Disclaimer: This is an advanced thread, I do not advocate beginner-to-intermediate divers ditching their octo.

In a thread about pony-bottles, the topic of whether or not to ditch your octo came up. Specifically, someone mentioned being unable to access your larger air supply, if you use a pony and ditch your octo. That brings up 2 interesting questions:

1. Has anyone heard about or experienced an incident where a 2nd stage is able to deliver air?
2. When does an octo become "ditchable?"

An "octopus" is not for self redundancy but strictly for air sharing, a pony provides full redundancy and of course can support a buddy in distress as well. I think perhps the thread you refer was in the solo forum? Wherein, third paragraph for the SDI solo diver courser manual:



I began diving long before the "octopus" second stage was in use and buddy breathing was the default air sharing method. If buddy diving is practiced in lip service only then I can see an "octopus" providing a partial redundancy but full redundancy is at minimum a pony or if truly practicing buddy diving, then your buddy. Solo diving is a different animal than buddy diving.

 

[rx7diver]

... How do you figure that you can inspect the diaphragm without disassembling the 2nd stage? ...

I think the procedure is to (when depressurized) blow out, and then breathe in through the regulator, and then you get no air if there is no leak. I keep forgetting about that procedure myself.

Yes, @SlugLife describes the procedure I was taught (in 1986 during my open water course) and still use: Mount your 1st stage on your cylinder, and connect all hoses. During your regulator check, at some point turn your cylinder valve off, depressurize your reg completely (using your purge button or your power inflator), and then place the second stage in your mouth, forcibly exhale through it a couple of times (to clear out any brown recluse spiders, scorpions, etc., that might have crawled in) without inhaling through it, and then gently attempt to inhale through it. You should NOT be able to inhale; no air should be able to enter this closed system.

Inhale gently, lest for some 2nd stages (e.g., Scubapro BA) you dislodge (suck in) a corner of the exhaust valve (which absolutely will cause the reg to breathe wet).

Do this for each 2nd stage or Air 2-like combination inflator attached to any first stage you're about to dive.

Don't forget to continue checking everything associated with your regulator.

This procedure should also alert you to a tear in your mouthpiece that your earlier visual inspection might have missed.

rx7diver