Double Tank Manifolds, Bad Idea!

[AfterDark]

Ill breath the fart out of a donkeys ass if it means not drowning. My point is that those last ditch plans aren't really practical and can't be relied on.

Which brings me back to an earlier post where I posted that reg, valves, O-rings (if changed regularly) hoses and such; malfunctions are so rare that configuration doesn't really mean much. When was the last time a diver's choice of configuration killed him/her?

 

[Doppler]

Even if you had a full tank (you probably wont), feathering it only buys you a handful of breaths.

Sounds like you have no experience to back that statement up. I have and can assure you that done correctly (as taught in a decent decompression procedures, helitrox or SM class), very little gas is wasted. In addition to running this drill in caves, and for real with deco bottles from as deep as 40 metres, I have intentionally breathed a simulated free-flow (purge depressed) from a small cylinder on a platform at 6-7 metres and compared the gas consumption feathering the valve with normal consumption. The numbers may have been a little off but 22 litres per minute compared to 16 litres per minute. Frankly, I think I could do better but have never gathered more data because frankly, with proper gas management, the whole scenario falls firmly in the laps of the Chance Brothers: Slim, Fat and Noe.

 

[Peter69_56]

I make that criticism as a matter of course in these discussions.

A lot of the talk of 'feathering valves' and 'swapping regs underwater' is great for the pool, but it really loses its appeal when its game day (deep, dark, silty, on the line, with a primary light, etc etc). A REAL freeflow on a reg drains your tank in a matter of like a minute. Even if you had a full tank (you probably wont), feathering it only buys you a handful of breaths. And a breath-hold while swapping regs is pretty outrageous. Putting a lot off eggs into one basket with that little maneuver.

Having managed a real life free flowing deco regulator I can state categorically that it doesn't just buy you a few breaths, when in real life conditions, it buys you a life if the chips are down. And this is not just some theoretical pool talk. Safe diving is about managing your diving no matter the circumstance.

 

[PfcAJ]

So Doppler says it doesn't significantly impact (significantly) on a platform (pretty pool like) and then Peter gives some info about a real life situation. Steve, drills and sterile environments aren't what I'm talking about. I'm talking about real deal stuff.

Peter, I'd love to hear more details, really. That's the kind of stuff I'm interested in. You said deco reg, shallow, deep, how much reserve, nature of failure, etc etc. All important details.

 

[_Slacker_]

I'm talking about real deal stuff.

I've feathered valves several times on SM and stage bottles for various reasons. Usually it is a short duration to sort through the issue, turn the dive, and/or not NEED the gas anymore. The longest I've feathered a valve was a dive with a free flowing reg. 2nd stage failed open, so I feathered the valve on/off to use gas out of the tank I needed to complete the dive without altering the dive plan. I did this for approx. 30 minutes and would say I lost minimal gas 10-20% over my normal breathing rate. You can get really good at doing it by charging the line just as you start to take a breathe and turning it off before you finish to drain as much as possible out of the line. Not a life or death situation because nothing else went wrong and I had plenty of other gas, but I was a scooter dive and 4000 ft back from the entrance.

 

[PfcAJ]

Curious as to the specifics of how you managed the light, scooter, and valve at the same time. Helmet light?

 

[AfterDark]

I've feathered valves several times on SM and stage bottles for various reasons. Usually it is a short duration to sort through the issue, turn the dive, and/or not NEED the gas anymore. The longest I've feathered a valve was a dive with a free flowing reg. 2nd stage failed open, so I feathered the valve on/off to use gas out of the tank I needed to complete the dive without altering the dive plan. I did this for approx. 30 minutes and would say I lost minimal gas 10-20% over my normal breathing rate. You can get really good at doing it by charging the line just as you start to take a breathe and turning it off before you finish to drain as much as possible out of the line. Not a life or death situation because nothing else went wrong and I had plenty of other gas, but I was a scooter dive and 4000 ft back from the entrance.

Sounds like it sucked, but as we say that's diving. It ain't all blue water and cocktails.

Job well done.

 

[_Slacker_]

No, I don't wear helmets when diving. Scooter and light in right hand, valve in left. Had the failure been on the other side, scooter and light would have gone to the other side, didn't change the pace of the dive for transit. The parts I had to take slow were inflating wing/suit, dumping gas, and picking up reels while using the same hand that was providing gas.

 

[TSandM]

I did some valve feathering in my recent class. I would imagine you could get good at it, but at my level of facility, I sure wouldn't want to depend on it for much gas that I really needed.

That said, it's got to beat having the same failure in independent doubles with the valve behind me, where feathering it would not be an option at all.

 

[DaleC]

But does it?

I've said before that I believe risk mitigation for solo diving has more to do with risk avoidance and maintaining contact with the surface than with staying at depth and dealing with a problem. So, what would be better: Staying at depth and attempting to breath from a feathered valve, or surfacing promptly with the reserves you know you have in your second cylinder. As a solo diver I know my pathway to the surface and what I need to get there. I keep that in each cylinder. Done. Those other skills, like feathering valves and manipulating isolators and posts are nice, but for me they only serve to delay getting to the surface. They get in the way of problem resolution.
When you have a system that works.. stop - don't add layers of unnecessary details, unless those details become necessary.