Hose routing on independent twin setup?

[sunkarm]

where can i read more to understand the basic knowledge of twin tank diving on the internet?

 

[Nemrod]

Long ago before there were off the shelf isolation manifolds we dove the caves with independent doubles and even triples. With the advent of isolation double manifolds there is no need for independents anymore (some travel situations may warrant). If your Artic dive guide insists just turn the isolation center knob to OFF. That just makes no sense other than perhaps he is behind the times and does not understand isolation manifolds.

I still have a set of independent doubles. They are on custom bands that are more narrow than most modern rigs and also allow a smaller third tank or battery pack (for our main light) to nestle between. There is no point in going into how we rigged them, I reassembled them more for nostaligia than any real need. N

 

[wedivebc]

If you and your buddy are diving independants what do you need a long hose for? There is no failure that can render you OOA.

On the other hand, if you are looking at these to be a substitute for manifolded doubles I urge you to do some more checking

I have done plenty of checking and I have not found any reason not to dive independants in any environment. Do you have any personal experience to the contrary?

 

[Nemrod]

If you and your buddy are diving independants what do you need a long hose for? There is no failure that can render you OOA.



I have done plenty of checking and I have not found any reason not to dive independants in any environment. Do you have any personal experience to the contrary?

If you have a problem on either side you loose that air supply. With an isolation manifold you may be able to isolate the problem and still retain access to that gas. N

 

[ianr33]

I can see the value of independants rather than manifolded doubles for diving in the Arctic.

I would imagine that your fingers might get a little chilly which could make operating an isolator valve kind of difficult?

In the event of a freeflow,change regs.Close the valve on the freeflowing reg if possible. if your hands are a block of ice forget the reg and just head to the surface.everything will be fine.

With manifolded doubles if you fail to close the valve you are in a world of hurt.

Sidemount MIGHT be the best option but needs a lot of extra gear. (My Nomad should arrive this week )

 

[wedivebc]

If you have a problem on either side you loose that air supply. With an isolation manifold you may be able to isolate the problem and still retain access to that gas. N

Yes but if you apply rule of thirds to your diving you should not need any more gas than what you have kept for reserve in each tank. At the furthest point in the dive there will still be 2/3rds in each tank. You turn the dive and the gas needed to ascend gets less as you get closer to the exit point of the dive. People who claim independants are less safe than manifolds have never thought it through, at least no one has come up with a compelling argument for it.
Manifolds are certainly easier to dive and convenient to fill.

 

[wedivebc]

I can see the value of independants rather than manifolded doubles for diving in the Arctic.

I would imagine that your fingers might get a little chilly which could make operating an isolator valve kind of difficult?

In the event of a freeflow,change regs.Close the valve on the freeflowing reg if possible. if your hands are a block of ice forget the reg and just head to the surface.everything will be fine.

With manifolded doubles if you fail to close the valve you are in a world of hurt.

Sidemount MIGHT be the best option but needs a lot of extra gear. (My Nomad should arrive this week )

How about this scenario. You are passing through a tight restriction on a wreck, your buddy is behind you. An LP hose snags on a jagged piece of metal and tears and huge stream of bubbles ensues. Your only avenue to shut down is to wiggle backwards far enough that you can get your arm up to shut the isolator but this may take quite a few precious seconds provided the hose hasn't now caught In the mean time the precolation from the bubbles has reduced vis to zero and your buddy has no idea what is going on.
Far fetched? No it happened to the guy who taught me tech diving and he was a big believer in indies.
Try removing a LP hose from a reg on a full tank and opening the valve for 30 seconds. You will be amazed at how much gas you lose.
Independand doubles will never render you with insufficient gas to exit, even with an overhead.

 

[*Floater*]

I have done plenty of checking and I have not found any reason not to dive independants in any environment. Do you have any personal experience to the contrary?

Sometimes when traveling, manifolded doubles aren't available, so you either have to dive single tanks, or independent doubles. And if renting, two single tanks are often cheaper than a twinset. Those are my only reasons for using back-mounted indies instead of doubles with a manifold.

 

[*Floater*]

I have the same SPG's, but I can tell them apart because the one for the left tank is clipped to the left hip D-ring and the one for the right tank is clipped to my right hip D-ring (Bryden buckle).

For gas planning, I start with the right tank (shorthose) and breathe a third of it, then switch to the left (longhose) and breathe 2/3 of it, and then back to the right tank. This way the tanks are never more than 1/3 apart in remaining gas, and I generally only need to make 1, or at most 2 switches. I usually have at least a third left in each tank at all times so in OOG situation both tanks would have enough for one person to make it out.

EDIT TO ABOVE: I meant short hose on left tank, long hose on right tank.

And yes, the short hose can be a problem. A buddy gave me an OOA sign (test) while I was diving indies and breathing the short hose. I immediately tried to donate the reg from my mouth (short hose at the time) with predictable results. That said, I havenn't bothered to change the setup since I use it rarely. If I were to switch the short hose to a second 7ft hose, I'd get one of Miflex hoses and I roll up and stow away 5' of it, and try to use the rest as a short hose, except it would have to be rigged so that the extra would come loose if I pulled on the short hose to donate it.

 

[ianr33]

Independand doubles will never render you with insufficient gas to exit, even with an overhead.

Hence my upcoming conversion to sidemount!

Seems to me that when things get "interesting" as in your wreck example you are effectively soloing. Same would be true for tight passages in caves or complete siltouts.Even the best buddy in the world is not much help if he can not see you.