The great independents versus isolation manifold debate
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Aviatrr
Contributor
It all depends on the type of diving you do. I started out on manifolded doubles(with isolator), and still dive those on occasion. Most of the time, however, I dive independents in the form of sidemount. I have considered removing the manifold from my banded doubles.
With a manifold, you do not have total redundancy. The manifold could fail in such a manner that you lose gas from both cylinders.
With independents, no single failure could potentially cost you all your gas. You MUST properly manage the tanks by switching often. Some people use 1/3 from one cylinder, then 2/3 from the other, then back to the first for the remaining 1/3 - and leaving 1/3 in each for reserve.....but I prefer to switch every few minutes, 300psi at the most. That gives me a better reserve should I have a regulator failure.....since I will notice it sooner.
How many people actually check their backup reg more than once during a dive? Most people check their regs just before descending, with their face in the water, or within the first 10-15 feet. What if that reg works fine at 15', but doesn't work at all for some reason at 100'? Next thing you know, you must donate your primary reg to an OOA diver at 200', and you end up with a reg that doesn't work. Not likely for both things to happen on one dive, some say....but maybe some people are diving with regs that have not worked at any significant depth for a long time. I check each of my regs every few minutes via my tank switching.
The main reason I prefer true redundancy, and take the additional risk of losing half my gas due to a reg failure, is that I often dive solo, or in places that I may as well be solo due to close quarters and inability to turn around to grab a reg from my buddy. Do I dive solo with manifolded doubles? Sure....but I carry a stage bottle, with the proper bottom mix, to use as bailout should my manifold fail. Total equipment redundancy.
Mike
Wreck/Tec
Contributor
Listen, you can say there are reasons for, or not, useing either. If you are good about serviceing your equipment you can pretty much eliminate burst disc and o ring failures. If you want the chance to salvage gas in the event of some kind of failure, or don't want to monkey around switching regs to ballance gas supplys use a manifold.
If your not bothered by the prospect of some kind of failure which would half your gas supply and switching regs frequently is not annoying, an independant system will be your ticket.
I personally want the chance to save gas and maybe my life! I service my equipment religously and feel o ring and other failures are remote, but not impossible. There is a difference between the two, they have been explained. Make an educated decision and live with it!
Wreck/Tec
If your not bothered by the prospect of some kind of failure which would half your gas supply and switching regs frequently is not annoying, an independant system will be your ticket.
I personally want the chance to save gas and maybe my life! I service my equipment religously and feel o ring and other failures are remote, but not impossible. There is a difference between the two, they have been explained. Make an educated decision and live with it!
Wreck/Tec
Self explanatory question really.
I am new to this and was taught to be independent. Since then I have had a number of friends say to go manifold (funnily enough they were taught this way).
Don't care if this discussion turns to religion or politics - just keen on the points of view.
My teaching - 2 independent regs with right and left delivery - one on longer hose. Must watch gas switching but removes need for too much valve futzing ? - Switch every 50 bar.
Personal practice adapted to breathe one on descent and immediately switch to second on bottom then switch every 50.
I am new to this and was taught to be independent. Since then I have had a number of friends say to go manifold (funnily enough they were taught this way).
Don't care if this discussion turns to religion or politics - just keen on the points of view.
My teaching - 2 independent regs with right and left delivery - one on longer hose. Must watch gas switching but removes need for too much valve futzing ? - Switch every 50 bar.
Personal practice adapted to breathe one on descent and immediately switch to second on bottom then switch every 50.
It's a trade off. The manifold makes things easier but you're more vulnerable to air loss if a reg starts to free flow. On the other hand without an isolator you're covered for air loss but you've got a problem when sharing air and if one of your regs bites it.
Personally I think you need a manifold with an isolator on it. When the isolator is closed you have independent doubles. with all of the advantages this gives you. When/if you get in a sitatution that you need to share air or one of your regs craps out you can open the isolator and have the advantage of the manifold.
R..
andibk
Contributor
Big Blue One,
I was taught independents also but a slightly different way. I have one regulator coming over the right shoulder and one coming over the left shoulder. On the left post I have a 3rd reg on a long hose and I stuff it in the side with bungy and sticks out right under my left arm pit where I can reach it quickly. As far as reg switching I breath one third of the right tank then switch to the left and and breath one third. At this point I have breathed a total of one third of my gas supply then I start to turn back to the ascent line. Now that I am back on the right regulator I still have two thirds of my left tank available if there is any problem and this is the tank I leave for emergencies.
Bruce
I was taught independents also but a slightly different way. I have one regulator coming over the right shoulder and one coming over the left shoulder. On the left post I have a 3rd reg on a long hose and I stuff it in the side with bungy and sticks out right under my left arm pit where I can reach it quickly. As far as reg switching I breath one third of the right tank then switch to the left and and breath one third. At this point I have breathed a total of one third of my gas supply then I start to turn back to the ascent line. Now that I am back on the right regulator I still have two thirds of my left tank available if there is any problem and this is the tank I leave for emergencies.
Bruce
I like the idea of the manifold turned off and only turned on when needed - but I thought manifolds were taught the other way around !!
This obviously means you still need two guages - is two guages generally a good idea - I was told with manifold you only need one but if the side with the guage craps out you are breathing on an unknown quantity ?
Also think the third hose on the left post and the 2/3 remaining on the left for any problem is good idea.
Bruce - how do you do the hose stuffing and bungy - new to this so not clear on how to "stuff"
This obviously means you still need two guages - is two guages generally a good idea - I was told with manifold you only need one but if the side with the guage craps out you are breathing on an unknown quantity ?
Also think the third hose on the left post and the 2/3 remaining on the left for any problem is good idea.
Bruce - how do you do the hose stuffing and bungy - new to this so not clear on how to "stuff"
detroit diver
Contributor
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A manifolded rig has all of the advantages, and none of the disadvantages of independent doubles.
When you breath down a set of manifolded doubles, the gas is reduced evenly in each tank. No weight imbalance, no having to remember to switch regs at a certain time, only one guage to look at. Simplicity. As mentioned, if a reg craps out, just shut down the valve and you STILL have use of both tank's gasses. You can't do that with independants. If the valve craps out, just close the isolator and you're back to a single tank.
3 hoses? Stuffed? For what? You've just added more potential failure points to your rig.
If a reg starts to free flow, just reach back and turn off the valve. You're not going to loose any more gas with a manifolded rig than an independant rig. And as said before, you still have that gas available to you thru the manifold.
Independants don't make any sense to me.
When you breath down a set of manifolded doubles, the gas is reduced evenly in each tank. No weight imbalance, no having to remember to switch regs at a certain time, only one guage to look at. Simplicity. As mentioned, if a reg craps out, just shut down the valve and you STILL have use of both tank's gasses. You can't do that with independants. If the valve craps out, just close the isolator and you're back to a single tank.
3 hoses? Stuffed? For what? You've just added more potential failure points to your rig.
If a reg starts to free flow, just reach back and turn off the valve. You're not going to loose any more gas with a manifolded rig than an independant rig. And as said before, you still have that gas available to you thru the manifold.
Independants don't make any sense to me.
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