Independent back-mounted cylinders

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Originally Posted by Serota

I am curious if anyone dives with non-manifold connected, back-mounted cylinders and, if so, how the rig is configured and used. Obviously, 2 spgs would be required, but are 2 long hoses used? What is the protocol for breathing down the gas; eg, switch regs. every so many psi used or other? Lastly, are non-manifold connceted tanks, regardless of where mounted, safer than manifold connected doubles?

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I dive non-manifolded, backmounts from time to time. The cylinders are inverted so that I can do shut downs really easy. The hoses have to be longer to fit.

Protocol is just like diving sidemounts (which I do mostly). A lot of my friends will dive independent backmounts in places that are big enough for them (usually not in the UK).

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Originally Posted by Duncan Price

I dive non-manifolded, backmounts from time to time. The cylinders are inverted so that I can do shut downs really easy. The hoses have to be longer to fit.

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There realy isn't much to do for a shutdown with independent tanks anyway. :)

If you have your regs and guages marked so that you know without having to think which one goes with which tank you just shut that one down and (if necessary) switch to the operating reg. (Assuming it's a freeflowing reg or visable hose that's effected). There is no center isolator valve to mess with and you are always isolated already.

If it turns out to be unisolable (HP relief tank o-ring or whatever) then open that valve and breathe that air down while the tank is still draining - saving the uneffected tank for later.

Sometimes just shutting a reg down and giving it a minute will fix a freeflow - and/or knocking sand/grit out of the thing.

Great topic!
With lots of real world experience.

I dive a mix of all 3 rigs (side mounted, independant back, manifolded back).

I caves I much prefer independants (either side or back mounted dependant on the size of passageway or kit of others I am diving with), if I end up in overhead environment or solo on a manifolded rig I tend to close the manifold - which means that one cylinder's gas is nearly as protected as if you were on independants.

I always swop regs every 20bar which keeps the cylinders no more than 10bar apart. As any failure is most likley to affect the cylinder with the most gas in it (murfy's law) this meens you have the maximum amount of gas possibe for your return journey.

However to add another idea into the pot, if you dive manifolded twins as idependants (ie with the manifold shut) this gives you most of the advantages of both systems.

I too dive non-manifolded back mounted doubles, and have been doing so for the past 15 years in both cave and OW enviroments. They make me feel safer when diving solo, plus you can assemble two individual tanks into a double set anywhere in the world, just using cam-bands, and you're ready to go.
I switch reg every 3/400psi, but lately I also use stages so leave the back-mounted tanks untouched most of the dive.
I would love trying the sidemounted configuration, but after so many years I am afraid to change a configuration I find myself so comfortable with; plus, my favourite cave has a restriction which is better passed with backmounts (I know I know that sides can be temporarily detached).
I also wouldn'r know how to handle stage and deco bottles with sidemounts, but I guess it's probably just as easy.
Every tank has three hoses: reg, spg and inflator (one for suit, one for BC), they exit parallel from my Poseidon firsts and cross behind my neck (rights go left and lefts go right).
I am sure there's a lot of space for improvement but again having used it so long, I just fear I'd have a hard time changing.