Gas Switching Methodology

[Blackwood]

The friendly "Has this been asked before?" button says I'm not being redundant, so here goes.


In another thread, a discussion about deco bottle methodology came up. I was personally trained that all the bottles go on the left (or on a leash to be brought forward when needed), and to use visual queues (specifically permanent MOD labels and once-off analysis tape) to determine which bottle is appropriate for each switch level.

I know there are other strategies, the most prominent probably being "Left Lean, Right Rich," i.e. if you have 50% and Oxygen, the 50% is on your left and the Oxygen is on your right.

The question came up: how does LLRR handle dives with more than two gas switches?

I speculated a couple of options (leftist leanest, rightest richest; use the Left then the Right and then send them both back to a leash, replacing them with the next set, placing them LLRR), but neither seem particularly likely to me.

Can any LLRR divers shine some light on this?

 

[JDostal]

When diving with two I like to have one on either side of me. And, just because I like consistency, I do tend to put the lean bottle on my left. But I do not in any way shape or form rely on the placement of my bottles to determine what is in them. I verify. Look at the tank, check the markings. Grab the reg, signal a switch. Turn it on, watch the SPG pressurize and then breathe.

I'm not a "true" user of the system as I don't depend on the placement...ever. I just like having a tank on either side.

 

[mania]

One of the divers I was doing trimix with used LLRR style. Till the moment there was OOA drill. And his long hose got completly stucked by the 100%O2 tank on his right. After this dives he changed the set up and moved all tanks to his left.

We tried OOA several tiems - each time he was not able to deploy the full lenght of the long hose - which in caves is sometimes crucial.

 

[JDostal]

I don't carry my deco tanks a whole lot when I'm cave diving. And if I'm cave diving I'm in sidemount so air sharing is a non issue

I've tested the hose deploy with this setup and have been able to do it. Who knows - could be a difference in the way the gear is placed on the right side.

 

[Blackwood]

One of the divers I was doing trimix with used LLRR style.

Two bottles or more?

 

[JDostal]

I should actually try some more dives with all the bottles on one side. When I did my first dives with multiple bottles I initially hooked them up on one side but everyone I was diving with said I should put one on each as it was a PITA dealing w/ them all on one. I've just kind of stuck with that method ever since. On big stage dives though I guess I'm stacking up a few bottles on the left already anyway...hrmm...maybe I just need to change my ways.

 

[Colliam7]

The question came up: how does LLRR handle dives with more than two gas switches?

With 3 bottles, the two leanest on the left, and the richest on the right. With 4, the same, 2 leanest on the left, 2 richest on the right. In either case where there are 2 bottles on one side, the options are to a) 'chest / hip' clip both bottles, with the leanest mixture on top, or b) 'chest / hip' clip the leaner mixture and hip clip (or leash clip) the richer mixture. Whether you transfer bottles from the chest clip to hip clip after use, bringing the richer bottle up, is to me a matter of personal preference.

Three additional comments: 1. I have not yet been deep enough / long enough to be in a situation requiring 4 bottles, outside of trimix training, so I can't offer first person comment on the challenges. Where I have used three, it has been the two leanest (including one bottle of bottom gas at times) on the left, and a 100% bottle on the right. I personally favor moving a used bottle to the hip clip position, but I don't know that it is somehow 'best'. 2. Agree with all the comments about clearly marking bottles, and rigorously using a set NOTOX switching procedure, and not relying only on bottle position, or hose / second stage color, etc. Having said that I use colored hose wraps on my 50% and 100% bottle regs, plus tie-wrap placements (as tactile cues in the case of silt out), in addition to the appropriate markings. 3. Trapping the long hose under a right side bottle is certainly a potential problem. But, it should not occur at depth during a gas switch because, ideally, the diver would have done a 'goofy check' at the surface to confirm that the hose was not trapped and the initial descent check should also include a test deployment of the long hose for the same purpose. Of course 'ideally' and reality may not always be the same.

 

[TSandM]

Thank you, Colliam! I'm glad somebody finally answered the question, because I was curious, too.

 

[Blackwood]

What she said. I've seen it suggested many times that RRLL can't handle dive with more than two bottles. I knew there must be some strategy.

Thanks Colliam.

 

[rjack321]

Colliam, it sounds like any full bottle is up front on your chest (up to 3 or 4)? But you sometimes put empties/used ones back on your hip? So you don't use (or need) a leash for a full bottle on the hip and "bring it forward" a bit before you want to breath it. Do you use a leash to stow empties or just use the nose boltsnap?
Just curious how the details of your system works for you. Thanks