Tom,
This is his rationale:
If your primary regulator has a catastrophic failure, and you have no redundant 1st stage on that tank(s), then for all intents and purposes the gas in that tank is not available to you.
You can switch to your redundant gas supply (bailout bottle) and surface, but whatever amount of backgas you still have is no longer available.
So, the H-valve (or Y-valve, or manifold, whatever) allows you to use your backgas if your primary regulator craps out. It provides you with a secondary access to your backgas.
Conversely, if your backgas fails due to <fill in the blank: tastes oily; is giving you a wicked headache, nausea, and vertigo; is unaccountably empty; or you're donating to some random OOA hoover who swam up to you out of nowhere and you're now watching your needle drop like a rock, etc.>, the bailout bottle allows you to switch to a clean, known amount of redundant gas that will allow an unhurried ascent with safety stop to be made. You can do a gas switch to your sling tank and allow the OOA hoover to suck down the rest of your backgas while you both conduct a safe ascent.
So...from the most conservative perspective, you would plan to have redundant access to your backgas, and a redundant gas supply entirely separate from your backgas.
Thats what your LDS was talking about when he made his recommendations.
Whether you agree with your LDS and choose to dive that way or not is another matter.
Regards,
Doc
This is his rationale:
If your primary regulator has a catastrophic failure, and you have no redundant 1st stage on that tank(s), then for all intents and purposes the gas in that tank is not available to you.
You can switch to your redundant gas supply (bailout bottle) and surface, but whatever amount of backgas you still have is no longer available.
So, the H-valve (or Y-valve, or manifold, whatever) allows you to use your backgas if your primary regulator craps out. It provides you with a secondary access to your backgas.
Conversely, if your backgas fails due to <fill in the blank: tastes oily; is giving you a wicked headache, nausea, and vertigo; is unaccountably empty; or you're donating to some random OOA hoover who swam up to you out of nowhere and you're now watching your needle drop like a rock, etc.>, the bailout bottle allows you to switch to a clean, known amount of redundant gas that will allow an unhurried ascent with safety stop to be made. You can do a gas switch to your sling tank and allow the OOA hoover to suck down the rest of your backgas while you both conduct a safe ascent.
So...from the most conservative perspective, you would plan to have redundant access to your backgas, and a redundant gas supply entirely separate from your backgas.
Thats what your LDS was talking about when he made his recommendations.
Whether you agree with your LDS and choose to dive that way or not is another matter.
Regards,
Doc
