"Complete Wreck Diving" (manifold vs independent)

[Soggy]

My contention is independant doubles are safer than manifolded doubles with or without a buddy. I am not talking about isloated manifolds or any contraptions here just a pair of good old tanks, back or side mounted doesn't matter.

My contention is that having a single regulator failure and needing access to the gas in both tanks is far more likely than having a catastrophic failure of the isolation valve (has it actually ever happened in the water?) which would require you to go onto your buddy's gas. I think that the problems added when you consider gas donation to your buddy on independents far outweighs the perceived advantage of having two completely separate systems. I don't trust that someone on a set of independent doubles would be able to get me gas from their long hose when I needed it. I also don't trust that someone jumping into the water with the mentality that they don't need to be able to donate is a qualified teammate.

I think independents could be considered a decent choice for solo diving because you *don't* have a buddy around and it is at least conceivably possible that the isolation valve could fail and there would be absolutely no one around to assist. If I were to solo dive, I would still dive with a manifold, however because I believe that chance to be much much smaller than the chance that I need access to the extra gas.

 

[wedivebc]

My contention is that having a single regulator failure and needing access to the gas in both tanks is far more likely than having a catastrophic failure of the isolation valve (has it actually ever happened in the water?) which would require you to go onto your buddy's gas. I think that the problems added when you consider gas donation to your buddy on independents far outweighs the perceived advantage of having two completely separate systems. I don't trust that someone on a set of independent doubles would be able to get me gas from their long hose when I needed it. I also don't trust that someone jumping into the water with the mentality that they don't need to be able to donate is a qualified teammate.

I think independents could be considered a decent choice for solo diving because you *don't* have a buddy around and it is at least conceivably possible that the isolation valve could fail and there would be absolutely no one around to assist. If I were to solo dive, I would still dive with a manifold, however because I believe that chance to be much much smaller than the chance that I need access to the extra gas.

The entire point of my argument is if you have all members of the team in independant doubles can you think of a situation where gas donation is even required? Not that it is even difficult in independats but we'll leave that alone for now.

 

[Soggy]

The entire point of my argument is if you have all members of the team in independant doubles can you think of a situation where gas donation is even required? Not that it is even difficult in independats but we'll leave that alone for now.

Problem with post, shutdown, switch to other reg and it's got gunk in it or has a torn diaphragm. There are a number of scenarios that aren't particularly unrealistic that would require gas donation.

It's no different a question than with an isolation manifold. I can only think of one gas loss related problem that requires donation in a set of manifolded doubles -- failure of the isolator itself, but I've never even read about that ever happening...but I still practice gas donation.

What scenario can you think of where independents solve a problem?

 

[wedivebc]

Problem with post, shutdown, switch to other reg and it's got gunk in it or has a torn diaphragm. There are a number of scenarios that aren't particularly unrealistic that would require gas donation.

Every practice, drill and contingency is based on a single failure on a tech dive. Primary light failure-switch to backup, thumb dive. Problem with post switch to backup thumb dive.
If you are suggesting multiple failure modes you are still better off independant because it is far easier to secure a backup reg bungied arount your neck than to locate buddy, get attention, secure his reg.
There are infinite possibilities and combinations of failure and we coul;d argue all day about this and that.
Lets not obfuscate this by adding multiple failures. I asked you how a person on independants could be less able to deal with a failure than a person with an isolator and you keep dodging the question.
You may be surprised to know I carry a long hose on my independants and practice s-drills all the time, but anyway...

 

[Soggy]

If you are suggesting multiple failure modes you are still better off independant because it is far easier to secure a backup reg bungied arount your neck than to locate buddy, get attention, secure his reg.

I am referring to a temporary loss of access to gas. These are problems that actually occur. You can call it a multiple failure if you want. I'm talking about reality....you shut your post down, grab your bungeed reg, and realize it's got a problem because you either rolled it off earlier without noticing or it got gunk in it when you were digging for that artifact earlier.

Gas donation is an essential skill for any diver. We can argue in circles about the likelyhood of it needing to happen, and I'll counter it with crap happens and that it's just as unlikely with an isolator manifold, yet it is still practiced religiously. There was a recent accident where someone had multiple freeflowing regulators under the ice and needed to get gas from his buddy. That could have easily been on independents, too. I wouldn't have wanted to wait while you fumble around unclipping a long hose (or however you store it when it's not in use). Unfortunately, that person died, but not because his buddy was unable to provide him with gas.

Fact is, isolators don't really have a high failure rate, and if they fail it's pretty much always on the surface. I dive with a buddy so I'll take the risk on that 1 in a billion chance that the isolation valve itself fails and I need to get gas from my buddy.

You may be surprised to know I carry a long hose on my independants and practice s-drills all the time, but anyway...

No, I assumed that you carry a long hose on your independents. My point is that you will not always be breathing off your long hose, so if I need gas from you, you will have to figure out which hose to give me rather than just donating what's in your mouth. That's yet another delay added in when I need gas now.

I won't even get into the advantages of, in a donation scenario, having both divers breathing from a single large gas source rather than two small sources.

And let's not forget that you've added another hose and SPG into the mix on independents which are far more likely to fail than an isolation valve.

 

[wedivebc]

I am referring to a temporary loss of access to gas. These are problems that actually occur. You can call it a multiple failure if you want. I'm talking about reality....you shut your post down, grab your bungeed reg, and realize it's got a problem because you either rolled it off earlier without noticing or it got gunk in it when you were digging for that artifact earlier.

Gas donation is an essential skill for any diver. We can argue in circles about the likelyhood of it needing to happen, and I'll counter it with crap happens and that it's just as unlikely with an isolator manifold, yet it is still practiced religiously. There was a recent accident where someone had multiple freeflowing regulators under the ice and needed to get gas from his buddy. That could have easily been on independents, too. I wouldn't have wanted to wait while you fumble around unclipping a long hose (or however you store it when it's not in use). Unfortunately, that person died, but not because his buddy was unable to provide him with gas.

Fact is, isolators don't really have a high failure rate, and if they fail it's pretty much always on the surface. I dive with a buddy so I'll take the risk on that 1 in a billion chance that the isolation valve itself fails and I need to get gas from my buddy.



No, I assumed that you carry a long hose on your independents. My point is that you will not always be breathing off your long hose, so if I need gas from you, you will have to figure out which hose to give me rather than just donating what's in your mouth. That's yet another delay added in when I need gas now.

I won't even get into the advantages of, in a donation scenario, having both divers breathing from a single large gas source rather than two small sources.

And let's not forget that you've added another hose and SPG into the mix on independents which are far more likely to fail than an isolation valve.

So you are saying in your training in the event of a failure you would go directly to your buddy as an alternate air source prior to switching to your own?
What makes your buddy's secondary reg any less likely to have a simultanious failure as your own.

Oh and try removing a spg and turning on the tank valve fully sometime. A blown HP hose will take about 10-15 minutes to empty a tank. Not a high risk failure point in my books.

 

[Soggy]

So you are saying in your training in the event of a failure you would go directly to your buddy as an alternate air source prior to switching to your own?

No, I didn't say that.

Oh and try removing a spg and turning on the tank valve fully sometime. A blown HP hose will take about 10-15 minutes to empty a tank. Not a high risk failure point in my books.

I'm aware of that. Joel Silverstein did a whole experiment. The risk is about the same as blowing your isolation valve. It is an additional failure point, though.

 

[Thalassamania]

My contention is that having a single regulator failure and needing access to the gas in both tanks is far more likely than having a catastrophic failure of the isolation valve (has it actually ever happened in the water?) which would require you to go onto your buddy's gas. I think that the problems added when you consider gas donation to your buddy on independents far outweighs the perceived advantage of having two completely separate systems. I don't trust that someone on a set of independent doubles would be able to get me gas from their long hose when I needed it. I also don't trust that someone jumping into the water with the mentality that they don't need to be able to donate is a qualified teammate.

I think independents could be considered a decent choice for solo diving because you *don't* have a buddy around and it is at least conceivably possible that the isolation valve could fail and there would be absolutely no one around to assist. If I were to solo dive, I would still dive with a manifold, however because I believe that chance to be much much smaller than the chance that I need access to the extra gas.

I don’t dive solo. I prefer independents. If I do not have a failure and you need gas … you get the long hose that’s in my mouth. If I do have a failure and you need gas … you still get the long hose that’s in my mouth. Both regulators have 5 ft. hoses, so it would make no difference to you. I am responsible for proper deployment and use of my backup, that’s not your problem except to assure yourself that I have a plan and can execute it.

The entire point of my argument is if you have all members of the team in independent doubles can you think of a situation where gas donation is even required? Not that it is even difficult in independents but we'll leave that alone for now.

This is true, it just them strokes with the isolation manifolds that have this sort of problem because they are not FULLY REDUNDANT! You’re ‘gonna die!

Isolation valves introduce the possibility of three new problems:

1. The isolation valve being closed prior to the dive.
2. The isolation valve being closed during filling of the cylinders.
3. Roll off of the left manifold valve.

 

[wedivebc]

I am referring to a temporary loss of access to gas. These are problems that actually occur. You can call it a multiple failure if you want. I'm talking about reality....you shut your post down, grab your bungeed reg, and realize it's got a problem because you either rolled it off earlier without noticing or it got gunk in it when you were digging for that artifact earlier.

I am not trying to defend the position that manifold is less safe you claim independants are less safe and I am challenging you to come up with a compelling (and factual) argument to support that. Give me some facts. I have a very open mind about this issue I just have yet to hear anything from the DIR crowd that supports their strong position on it. It is the same mentality that prevents them from using sidemount in a cave when clearly it is a superior setup in many situations.

 

[Soggy]

Both regulators have 5 ft. hoses, so it would make no difference to you. I am responsible for proper deployment and use of my backup, that’s not your problem except to assure yourself that I have a plan and can execute it.

How do you route the hoses?