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Octo or not?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Omni

New Member
Jul 21, 2004
5
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With double tanks do you run a octopus or not? You already have two regs and the ability to shut off the manifold if problems occor. So do you run a octopus, and if so why?
Also do you run two SPG's or just one? I have been told that since you turn the dive if you need to shutdown one side of your tanks you dont need to worry about double SPG's. But others have argued for a spg on each regulator. What is your opinion?

Omni
 

Mako25

New Member
Jul 14, 2004
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I only have a very limited experience with doubles, but, we (the shop I worked for) would not use an octo, but had an spg on each reg. no deapth/compass just the spg. although I have seen guys with a 3 in 1 console on one side and a 2 in 1 on the other.

I think a couple guys had an octo on a longer hose, like 7feet. But, they said they did that only when they were caving.
 

jeannette

Tech Editor
Feb 28, 2003
10
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Hi Omni,

It's generally regarded as not necessary to run an octopus when using doubles. There are lot's of arguments for this; I decided that it wasn't necessary because I have a spare on the other side. If I am having a bad day and I am on my secondary when my buddy also needs assistance, then I assume I will be run over by a bus upon surfacing :D
Seriously, I tend to also make a small assumption that unless my buddy is in dire need, he is as self-sufficient as I am and probably won't need if - if he does we will air share.

I tend to use one or two long hoses. Always one to get your buddy out of tight spots and so that you can give each other space if sharing gas.
I also use one SPG - for the reason that you mentioned, I use this on the regulator that I don't breathe from so that if I shut down my primary I have my gauge on the secondary.

It's really personal on lots of things, but I tend to carry only what I believe that I need for the dive and the emergency scenarios that may present themselves.

Regards
Jeannette
 
L

londonsean69

Guest
When I dive a twinset (what we call doubles in the UK) I have them banded together with an isolation manifold, 1 small spg, 7ft hose on right hand post, which is breather and if required donated to OOA diver, MY backup comes off the left post and is bungeed around my neck. I only use 1 SPG because if I had to do a valve shutdown, the dive is over, unless it was something like a roll off after contact with a reg. That is also why the long hose goes on the right post, it can only really be rolled 'on', therefore if it jams, the long hose is still available for an air sharing exit.
This is the DIR setup that is gaining popularity, although I wouldn't ever say I was a DIR diver.
 

Norman

New Member
Jun 25, 2004
1
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I dive one second stage on each first stage. This keeps it simple and clutter-free.
Norm
 
L

londonsean69

Guest
Norman, what about your spg, bcd inflate etc.??

I have one second stage to each first stage, but I also have all the other necessary hoses to attach.

It seems from your post that you dive independent singles, which is what I started out with, is this the case??
 

FreeFloat

Underwater Tourist
Jun 5, 2003
114
29
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There is a school of thought that all low-pressure hoses should at some point 'cross over' each other across the back of the neck.

Using that logic you would have:

Right post:
- primary on 7' hose
- wing inflator

Left post:
- backup, bungeed around neck
- SPG
- drysuit inflator

Doing it this way should also ensure a pretty clean hose routing.

Edit: This assumes you're diving manifolded doubles with an isolation manifold.
 
Last edited:

Josh

New Member
Sep 24, 2004
14
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0
Although everybody have their personal opinions (which is fine as long as they have reasons for those opinions) I personally believe each diver should try many different configurations with their setup and decide for themselves. There is nothing wrong with asking others and getting their opinion, but keep in mind it is just that, an opinion.

That being said here is how I usually dive my doubles:

I run my short hose on the left post. This is my breather. Personally, I do not want to have to take a reg out of my mouth to give to someone else. Also, I would rather be breathing of the post that could possibly roll off, so that I know when it happens, and can fix it. I do not want to give my breather to somone, and then put my backup in just to realize it has rolled off! I belive this could create more stress than just breathing off the left post, and possibly having to reach back and turn the valve back on.

I run my long hose off the right post. This is run through my "bondage" bands (which is a totally different discussion...ha ha ha) and to a surgical tubung loop around my neck.

I use a Suunto Vytec (hoseless air-integrated) on my left rist, therfore the transmitter is on my left post.

I have a dual bladder BC, but I only hook one up. I figure I have my Dry suit as a back up, and if I really need the second BC bladder I could just switch the inflator hose to that bladder.

I have specific reason to do, or not do certain things. I am not saying my configuration is perfect for everybody, or me for that matter. It is just where I currently am in the evolution of my diving philosophy.

Anyway, hope this gives you a different perspective. Good luck.
 

John A

Well-Known Member
Sep 15, 2004
118
13
108
Josh,

You make some valid points but I some of your reasoning has not been completely thought out. An OOA diver is instinctively going to go for your “breather” as you call it, that is the one that should be on the long hose and fully accessible. While breathing the long hose and having it across your chest, you can immediately free up 5’ of hose for the OOA diver, and a flick of the wrist gets the rest, your back-up reg (left post) is bungeed under your chin and pops right in your mouth, you are sure that the left post has not rolled because your spg is off the left and hopefully you have been monitoring it, but for argument sake, if it has rolled, you know that your power inflator is off the right, so it is just a matter of taking a breath off of it and opening the left post. Furthermore, if the OOA situation is minor (quickly solved problem), your system requires 2 divers to re-stuff the hose, breathing the long hose and taking it back is no problem to re-secure since it just tucks in your right side and makes the single loop around the neck. Stuffing also allows for the long hose being “grabbed” by objects protruding from a wreck or cave and extending out before you realize it, and again requiring 2 divers to fix the problem. Also, when gas switching for deco, your primary has now been clipped off, if there is a problem during the switch, you must fumble for one of your “parked” regs, by having the left post bungeed around the neck, it is just a matter of again chinning down and grabbing the neck reg (short hose) while solving the problem. You are also able to avoid large loops of hose hanging away from your body by diving the long hose, the neck reg can be kept on a very short hose and does not go out past your shoulder and the long hose is routed to do the same, creating less drag and chances for snag. This is my configuration for tech or rec, I dive and breath the (7’) long hose and have the short hose tight under the chin.
If you keep the “breather” and hand off the long hose that has been parked at best your are handing off a reg that is de-tuned and full of water, at worst there may be “stuff” in it that goes into the mouth of the OOA diver that creates more panic as he now forcefully grabs your working reg and now you must deal with 2 problems, or just hope that your long hose is still where you parked it when you go for it. This is just some of the many problems that can arise by not handing off your primary.
 

Josh

New Member
Sep 24, 2004
14
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John,
Yes you do make good points. And yes I have thought about those situations. I still choose to breath the short hose off of the left post. Personal preference I guess. I believe there are advantages to doing both. I am not sying one way is right, and one is wrong. I am just trying to show that there are many different ways to configure your gear :D I appreciate your comments - of course I am always willing to listen to others opinions.
 

UKDiver

Well-Known Member
Oct 3, 2004
21
1
88
48
Some good points by all here, I run a configuration similar to FreeFloats on my twins.

My reasoning for having only one SPG is that the more hoses you have attached, the more portential failure points you have. Also if you have to do a shut down, the dive's over.
 
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FreeFloat

Underwater Tourist
Jun 5, 2003
114
29
0
UKDiver said:
My reasoning for having only one SPG is that the more hoses you have attached, the more portential failure points you have. Also if you have to do a shut down, the dive's over.

My thoughts exactly. Keeping it simple is the name of the game. Besides, since your primary everything is on the right, it makes sense that should you be breathing off your backup (ie off the Left post) your SPG will still be active since that post is still on. If for whatever reason you shut off 9or rolled off) your left post you'd know it, or find out about it right quick when you checked your SPG.

Normally when diving your isolator stays open and your one SPG will thus tell the pressure for both tanks. The only place for 2 SPGs would be on sidemount or other independent doubles.
 

tom yerian

New Member
Sep 26, 2004
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Only a stroke would would think of confusing themselves with two spg's.One spg on the left post. Iwould be willing to bet that some of you tech. divers here still use 80% as a deco. gas too!Well, more on that later if interested.
yid... CAPT. TOM YERIAN
 

mic couzens

New Member
Dec 8, 2004
14
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tom yerian said:
Only a stroke would would think of confusing themselves with two spg's.One spg on the left post. Iwould be willing to bet that some of you tech. divers here still use 80% as a deco. gas too!Well, more on that later if interested.
yid... CAPT. TOM YERIAN
tell me more about the 80% :) thing
 

Jon

Dairyland diver
Supporter
Apr 7, 2001
4,080
473
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While I won't go around name calling, like Capt. Tom likes to do, this would most likely be "his" response:

A (baker's) dozen reasons why we do not use 80/20:

1) This gas was introduced in an effort to overcome the inability of unqualified student "tech" divers to control their buoyancy in open water, and is as such is yet one more concession to doing things in a convoluted fashion to offset a self- inflicted set of problems brought on by the "doing it wrong" thinking that pervades diving today.
2) A heavy sea is not a problem for a deco stop if it is not posing a lung-loading problem. Look at your depth guage in a heavy sea and "see" for yourself what the changes are - insignificant, and if they are not, you should either not have been diving or incurring a decompression liability of this magnitude in the first place. In the event of a change in conditions during the dive, see below where the 80/20 becomes a liability rather than an assett.

3) In the interest of using a standardized set of gases for which you can permanently mark your bottles , it is a poor concession to inability to sacrifice the benfits of pure O2 to accomodate a real or percived lack of skill - learn to dive before taking up techdiving.

4) In this same interest you will find that when you graduate to real diving, as in caves, you will not want to accellerate your ppo2 at lower depths while still being faced with a long decompression at shallower depths, and making bizarre mixes to do this is a dangerous mistake (just like the fantasy of holding an accellerated ppo2 on a rebreather throughout a deco). I am anticipating the thinking that the 80/20 crowd would then go to an additional oxygen in cave without accounting for total exposure, and subject themselves to the risk of tox in the final deco steps. Tox you do not get out of - bends you do.

5) The 80/20 mix is in fact totally useless and contraindicated as a deco gas. At thirty feet it is only a 1.52 ppo2 ( the real 1.6 ppo2 gas would be 84/16) and as such does not either provide the right oxygen window, nor does it does it work as well as pure oxygen without an inert gas at any depth. The gas mixing in your lungs has already lowerd the effective ppo2 enough to prevent spiking at 20 feet anyway with the use of pure oxygen - in other words, we aer dealing with a simplisitc misunderstanding here, or "old wives tale" that is typical in diving.

6) If 100% oxygen is a percieved buoyancy control risk at 20 feet, then why is the same ppo2 ( intended) not a risk at 30 feet? This shows the total lack of reasonable logic involved in the decision to use this gas, as well as a lack of understanding of the whole picture ( see the rest of this discussion).

7) Along those lines, all we hear is howling about "oxygen cleaning" above 40% mixtures, and dive shop proprietors on here complaining about scuba tanks with oxygen in them being filled in their shops. With a pure oxygen system, the tank only ever gets filled with oxygen from oxygen tanks, not from every dive shop compressor it sees. Again , this shows the total inconsistency of agency thinking, and reveals that the true reason for this gas is to pretend to lower liability for teaching incompetents to dive, which is bull, and to attempt to accrue some inventive accomplishemts to the dive agency pundits who themseleves prove that they do no real diving by making this recommendation in the first place. This is like the colored regs, the stages on either side, the quick-release buckle, and the poodle jacket: nonsense of the most obvious nature developped through one-dimesional thinking by those whose universe of understanding is not only severly limited, but blinded by the hubris of not being the "inventor" of the techniques that work.

8) Any perceived decompression benefit of using a higher ppo2 at 30 feet with 80/20 is then given back by the lowered ppo2 at 20 feet, not to mention the fact that the presence of the inert gas in the breathing mixture defeats the purpose of using oxygen in the first place ( see the Physiology and Medicine of Diving) . The ppo2 of 80/20 at 20 feet is 1.28, not much of an oxygen window, and at 10 feet it is 1.04 - useless for deco. To make matters worse, you can not get out from your 30 foot stop in an emergency ( not doing the other stops) on the 80/20 mix without really risking a type 2 hit.

9) This is a dangerous method to achieve a greater total volume of gas for the bad breathers (another obvious reason the gas is in vogue), who should not be incurring these decos, and even that benefit of having more gas is lost since it is breathed at 30 feet, and then has to last for the other stops. The fact is that gas is effecively saved by using the lower deco gas up to this point, relying on the pressure gradient to both achieve the deco and provide a break from high the previous gas's higher PPO2 prior to going to pure oxygen where the spike could be a problem on an extreme exposure without an adequate low ppo2 break ( again this shows that the 80% user is a neopyte diver with no real experience or understanding of the true risks of these dives) .

10) The 20-30% longer 30 foot time on the lower ppo2 is not only overcome on the pure oxygen at the next stops, the breaks do not come into play until the initial good dose of pure oxygen has been absorbed, since you are not spiking from a high pervious dose without a break that is effectively achieved on the previous gas. These things need to be understood and taught by the agencies, not some superficial convolution that is designed to obfuscate the problem rather than openly acknowledge and deal with it in a responsible fashion.

11) In an emergency situation, getting onto the pure O2 for 20 minutes or so (for long dives something approximating the bottom time or a any decent interval) would give you a real good shot at getting out of the water having missed the rest of your deco and living through it with pain hits only. You have to think these things all the way though, not go for the transparent superficial thinking of those who merely are trying to "make their mark" with some "great" idea they can call their own. The acid test is , as always, is the caliber of the divers who adopt these practices.

12) If there is some problem with your deco or you otherwise develop symptoms and need oxygen either on the surface or back in the water, it is silly to have not had it there all along. 80/20 is a joke for that purpose, unless you have asthma, in which case any accellerated oxygen mix would be a nightmare. This is again part of the "thinking it all the way through" phiosophy which is obviously mising from the 80/20 argument.

13) Only a card-carrying stroke would do somethng like this, and showing up with 80/20 is no different than wearing a sign on your back saying "I am a stroke, and have the papers to prove it". It announces to all the world that you have no clue, kind of like wearing clip-on suspenders or having dog dirt on your shoes.

George Irvine Director, WKPP "Do It Right"


BTW: I have used both 80% and pure 02 and prefer to use pure 02 all the time for simplicity sake.


Jon
 

Amphibious

Working Class Spearo
Mar 17, 2002
2,775
300
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if I'm diving doubles with an isolation manifold I will only have one SPG and a 2 regs, a primary on a 7ft hose and a secondary on a 22" hose on a bungie around my neck. if I'm diving independent double or sidemounting (look out the "stroke" police are comming! AKA elitest dinks :hmm ) I will still use a single reg per bottle, but 2 SPG's one per bottle. Somtimes you just can't get manifold doubles when you're traveling.

remember - anyone calls you a stroke don't even waste your time diving (or listening) to them, configure your gear as best suits your needs. good luck.

who cares if you use 80% ? sometimes you're diving in places where you don;t have a choice :hmm
 

tom yerian

New Member
Sep 26, 2004
43
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Absolutly correct Mr John, All who read your bullet proof answers to the 80% deco. gas treatis should take it to heart, especially divers in your part of the world, who dive in that frigidcold water. The colder the water the more n2 absorption, and trying to use 80% as an efficient offgas mix could find themselves in a bit of trouble. It's not even efficient in the warm tropical waters let alone in cold channel water.
As to name calling? If you are refering to the word ''stroke'' its use was intended for those divers who are, lets say, less than proficient.I made no direct comment at any single person, except to one mr. Amphibious, who singled me out to lambast me with his less than kindly remarks.I was informed that several people had a tissy over some of my remarks. Well, I hope they were as upset at his remarks as they were at my response to his.That said, all of you who have read his response to the use of 80% o2 as a deco.gas, take his advice, It is a sub standard mix. Do the math your selves.Technical diving is a serious business. If your gonna do it, do it right!

YID: Capt. Tom Yerian
 

tom yerian

New Member
Sep 26, 2004
43
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0
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Theres no excuse to use 80%. if you can get 80 you can get 100.! I hope that in the course of your diving career, you don't have a problem and really needed 100%, I would hate to be one of the thoughts on your mind when your re-thinking your position on deco. gas choice.I am a recompression chamber tech. and treated over a hundred cases of (Age,)and ( DCI) treatments. Well, have a good day!

YID: CAPT. Tom Yerian
 

Amphibious

Working Class Spearo
Mar 17, 2002
2,775
300
0
40
tom yerian said:
Theres no excuse to use 80%. if you can get 80 you can get 100.! I hope that in the course of your diving career, you don't have a problem and really needed 100%, I would hate to be one of the thoughts on your mind when your re-thinking your position on deco. gas choice.I am a recompression chamber tech. and treated over a hundred cases of (Age,)and ( DCI) treatments. Well, have a good day!

YID: CAPT. Tom Yerian

never said it was the best choice. if you wanted to go that route it would mean longer deco and greater surface intervals. very doable, but not first choice.

trust me, if I get in the shit underwater you won't have to worry about me thinking of you :wave
 
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