The great independents versus isolation manifold debate

[MaxBottomtime]

Im looking for opinions concerning rigging a back plate with independant doubles vs. isolation manifolds; the way I understand it there is a ressurgance of divers perfering independant cylinders citing problems with manifolds such as roll off, entanglment, more points of failure, if any of ya'll have opinions I would appriciate them,

Ther is little chance for a rolloff. If you manage to drag your valve knobs along a surface long enough to close them, you would likely be dragging the back od your head as well. The risk of entanglement is the same with a manifold as with two valves/regs from independants. As the last poster noted, an isolator failure is extremely remote. Most manufacturers now use the double barrel o-ring design. With independants, if one reg fails or freeflows, you've lost all gas from that tank. With an isolated manifold, you simply close the valve on that side and you still have access to all of the gas from both tanks.

 

[fgray1]

What I would like to see is all you guys do a valve drill and shut the the valves off in and Emergancy. I've seen some people do it with out the stress and I have to say it's time consuming. A free flowing tanks takes about 30 seconds to empty add the stress factor and I dought most of you could shut the valves off before the gas is gone. At least if I have indepants and they are side mounts I can see the problem and deal with it fast and decissive. Even to the point that if need be switch the regs out. And you won't need a wrench to do it. Of course we are talking a catostofic failure here.
If it's a slow leak then it's no big deal either way.
For my money I'll stick to indepandent systems. it allows for complete redundancy. I can even hand you a bottle if need be when your system takes a crap.
Just one mans opinion
Fred

 

[fgray1]

Ther is little chance for a rolloff. If you manage to drag your valve knobs along a surface long enough to close them, you would likely be dragging the back od your head as well. The risk of entanglement is the same with a manifold as with two valves/regs from independants. As the last poster noted, an isolator failure is extremely remote. Most manufacturers now use the double barrel o-ring design. With independants, if one reg fails or freeflows, you've lost all gas from that tank. With an isolated manifold, you simply close the valve on that side and you still have access to all of the gas from both tanks.

Gee that roll off I had 2 weeks ago must have been my Imagination then. Not to mention the guy I saw with the busted Knob on the manifold.
Fred

 

[wedivebc]

Im looking for opinions concerning rigging a back plate with independant doubles vs. isolation manifolds; the way I understand it there is a ressurgance of divers perfering independant cylinders citing problems with manifolds such as roll off, entanglment, more points of failure, if any of ya'll have opinions I would appriciate them,

I have been diving with either independent tanks or more recently manifold isolator closed for several years now. I have a long hose on the right post and begin my dive breathing the long hose then switching to left post regulator which by the way is converted to left hand hose position after breathing 1/3 of the gas. I then remain on the left regulator turning the dive at 1/3 from left side but continuing on the left untill 2/3s are used. I then switch back to right side. I don't find this a great task loading and I do it every dive.
The worst failure I have seen under water was a LP hose snag and rupture. The diver was a trained and experienced trimix diver and it took him a numer of seconds to sort himself out (maybe 20) In that time he had lost about 500psi from his double 98s and luckily it was a no overhead dive because he was well into his last 1/3rd. I firmly believe in this system and if in doubt try removing a second stage and then opening the valve to se how much gas you lose.
Very interesting thread....

 

[DEEPLOU]

What I would like to see is all you guys do a valve drill and shut the the valves off in and Emergancy. I've seen some people do it with out the stress and I have to say it's time consuming. A free flowing tanks takes about 30 seconds to empty add the stress factor and I dought most of you could shut the valves off before the gas is gone. At least if I have indepants and they are side mounts I can see the problem and deal with it fast and decissive. Even to the point that if need be switch the regs out. And you won't need a wrench to do it. Of course we are talking a catostofic failure here.
If it's a slow leak then it's no big deal either way.
For my money I'll stick to indepandent systems. it allows for complete redundancy. I can even hand you a bottle if need be when your system takes a crap.
Just one mans opinion
Fred

Judging by your location and side mounts, I will take a wild guess that you mostly do cave diving.
I am sure it is a lot easier to get to those valves under your armpits than on your back. But don't see too many people doing sidemounts on Ocean wreck dives (unless close quarters penetration is planned).

I use manifolded doubles, and practiced getting to those valves for about 20 mins this morning in the quary.
You have a point about time it takes to get valves closed.

There are numerous arguments on both sides of this issue. Although I use manifolded doubles, I don't have a problem with using independents. (have done and do do both)
With the type of diving I do, I don't see problem w/roll offs. It is clear that w/the type of diving u do, there is a consideration for such a problem.

just my $0.02