I won't speak for DaleC but a pony bottle (bailout bottle) isn't a deco bottle and it isn't a fact that turning the bottle off is "the best way". It is in your opinion which is fine.
I leave the bottle on. It's not a deco bottle that is 100% necessary on every dive. It's a bottle that is rarely necessary but when it is necessary it may not be the best procedure for the suddenly OOA diver (broken hose or whatever) to have to remember to turn the tank back on or to have to remember to keep re pressurizing the tank throughout the dive.
I check my pony bottle gauge from time to time during the dive. I don't need to turn the bottle off. For someone who is already trained to do that for their deco gas that might be the best approach should they decide to use a pony bottle. Most who are trained in deco diving don't use pony bottles however and would just use their doubles (I guess).
That pretty well sums up my thoughts too. On or off doesn't really matter as much (I dive with buddies that do both) as that you understand the pros and cons of each system and are well versed in the system you choose. If you sling your pony (so you can monitor gas loss and manipulate the valves) one is not intrinsically better than the other.
I'm NOT wanting to be confrontational, just to explore this a bit. What you are suggesting is that such a diver is likely to be highly stressed and already to have a high workload? So any extra operations beyond those immediately essential to maintain life cannot be entertained? This to me suggests a serious deficiency in training. A diver who is "on the edge" as this suggests is not a safe diver, nor is likely to be a comfortable one.
A pony
is intentionally used under stress conditions (OOA, catastrophic gas loss) a deco or stage bottle is not. With a stage/deco bottle one plans the gas switch and does it in a controlled fashion (usually). With a pony (used as a redundant air source) something "unexpected" has happened. For example:
- A burst disk, extruded O ring or severed LP hose is dumping 80cuft of gas in my ear.
- An OOA diver swimming up and grabbing my pony reg, trying to breath and finding it dead. Then, either trapping my hand as I try to turn the valve on or undoing the yoke valve themselves by mistake.
Everybody can dive their gear their own way. That is the beauty of scuba. For me I choose to have all regs live. I weigh the risk of losing my pony gas against the risk of breathing a dead reg in an emergency. If I do lose gas somehow I will notice it and can adjust my dive accordingly. This will be done under
non stressed non lethal conditions. If I, or someone else, breathes a dead reg and needs to turn the valve on this will be done under
stressed lethal conditions. I choose to take on the non lethal risk that I will deal with under non stressed conditions rather than the lethal risk I will deal with under stressed conditions.
But that's just me. I've thought it through and understand how my decision affects me.
It is often the case here on the board that people disagree on gear configuration and denigrate the others choice by claiming a lack of skills or experience. I think there can often be more than one right answer to a question and this is one of those cases. There really is no "better choice".
I think this may be disturbing to some who think that, if they have/do all the best things they will be safe. I subscribe to that to a certain extent but also realise that there is no "one" way that will protect me from the everchanging unpredictale nature of life.