Double Tank Manifolds, Bad Idea!

[AfterDark]

So in your first post, you outlined the number one reason for the manifold: if a reg fails (by far the most common failure in the gas system), you still have access to both tanks. Plain and simple. You went on to say 'if you planned your dive right, you should have enough gas to get home'. Something to that affect. The truth of the matter is that failures of generally any type are often accompanied with reduced vis and/or delays. You need that extra gas, and the manifold provides access to that gas.

Ain't that part of the planning for you?

 

[tskovan]

tskovan;

first let me say that I am certified to both side mount and back mount and i really like the maneuverability i get with side-mount but I am in the process of undergoing intense overhead environment training and would not even think of diving side-mount at this time..

I know in you post you said that overhead environments are of no interest to you, but that is where manifolded doubles becomes a requirement. Under IANTD manifolded doubles are required for overhead environment training if not training in a CCR.

the reason for manifolded doubles is easy, gas management simplicity. with manifolded doubles I have 2 shut off valves 1 for each of my second stages and a shut off valve on the crossover in the event that I loose an O ring on one of the tanks ( highly unlikely on a 300bar valve). the cross over is always left open period unless you loose an O ring, so fills are a none issue.

the big difference between side mount doubles and manifolded doubles is gas management. on the side mount configuration I have to gas match my tanks within 500PSI of each other to account for a complete failure of one of my tanks so that I can safely make it out of a cave. At depth dealing with narcosis and the heavy task loading ( running a reel or navigation) this becomes more difficult to remember to do and it is possible to find your self over 1000PSI off on your tank balance. A tank failure can then quickly become a serious issue and you might have become a statistic.

I know many people are switching to side mount in over head environments because its easier to get in and out of the water,but until they can handle a high level of task loading I think they are asking for complications on their dive.


Sent from my iPad using Tapatalk HD

Thanks for the thoughful responce, you made many valid points, some that I hadn't fully conciderd. I still think for non-cave diving that IDs are a better choice, for all the reasons I made in my OP, but you have given more to think about, Thanks.

---------- Post added September 18th, 2013 at 06:54 AM ----------

Message to the OP. You are invited to sit in on any class I teach... perhaps Intro to Tech would be a good one... to learn the basics of gas management and gear configuration.

I think you might learn something that would further your understanding and influence your analysis.




By the way, I no longer dive manifolded doubles.

Why not?

 

[DaleC]

I also dive ID's (though I am moving to SM in that regard for convenience sake) and have often argued some of the same points the OP has, though not in the same us vs them way.

Every configuration has its +'s and -'s. To argue which is better is like debating 4door vs coupe vs pickup vs motorcycle. We choose based on familiarity, purpose, a sense of belonging and personal preference.

For myself, I have always come from a solo diving perspective in gear configuration in which completely dependable redundancy outweighs usable gas. I will also trade actions needed in a non stressed environment for actions needed in a stressed one to achieve that. For those reasons, ID's make more sense.

Others may choose differently. I don't think that makes their decision any more or less valid than mine. A good debate is always healthy (IMO) as it causes one to think about their choices and perhaps some assumptions they may be making. But if you are diving safely, and having fun, who cares what the other guy does (or doesn't) do.

And I have L/R valves. I actually have an isolation manifold I (very) occasionally use and take the valves from there.

 

[Doppler]

Why not?

After 20 plus years of abuse lugging doubles around, my T3/T4 vertebra are damaged and I have been advised not too. This conveniently coincided with a decision to dive sidemount when the task at hand called for an open-circuit solution.

 

[tskovan]

I also dive ID's (though I am moving to SM in that regard for convenience sake) and have often argued some of the same points the OP has, though not in the same us vs them way.

Every configuration has its +'s and -'s. To argue which is better is like debating 4door vs coupe vs pickup vs motorcycle. We choose based on familiarity, purpose, a sense of belonging and personal preference.

For myself, I have always come from a solo diving perspective in gear configuration in which completely dependable redundancy outweighs usable gas. I will also trade actions needed in a non stressed environment for actions needed in a stressed one to achieve that. For those reasons, ID's make more sense.

Others may choose differently. I don't think that makes their decision any more or less valid than mine. A good debate is always healthy (IMO) as it causes one to think about their choices and perhaps some assumptions they may be making. But if you are diving safely, and having fun, who cares what the other guy does (or doesn't) do.

And I have L/R valves. I actually have an isolation manifold I (very) occasionally use and take the valves from there.

well put and I completely agree with you, the point of my OP was to see if I was missing something, (manifold doubles being so popular), so far I don't think I am. Maybe I should have put a question mark after the title instead of an exclamation point, some people are pretty thin skined.

 

[Teller]

I also dive ID's (though I am moving to SM in that regard for convenience sake) and have often argued some of the same points the OP has, though not in the same us vs them way.

Every configuration has its +'s and -'s. To argue which is better is like debating 4door vs coupe vs pickup vs motorcycle. We choose based on familiarity, purpose, a sense of belonging and personal preference.

For myself, I have always come from a solo diving perspective in gear configuration in which completely dependable redundancy outweighs usable gas. I will also trade actions needed in a non stressed environment for actions needed in a stressed one to achieve that. For those reasons, ID's make more sense.

Others may choose differently. I don't think that makes their decision any more or less valid than mine. A good debate is always healthy (IMO) as it causes one to think about their choices and perhaps some assumptions they may be making. But if you are diving safely, and having fun, who cares what the other guy does (or doesn't) do.

And I have L/R valves. I actually have an isolation manifold I (very) occasionally use and take the valves from there.

well put and I completely agree with you, the point of my OP was to see if I was missing something, (manifold doubles being so popular), so far I don't think I am. Maybe I should have put a question mark after the title instead of an exclamation point, some people are pretty thin skined.

I think you answered your own question. Access to all your gas in the event of a failure. Thats the benefit of manifolded doubles. With independent backmounted doubles if you have a failure you just lost half your gas. Sidemount is a different story.

 

[Slamfire]

the point of my OP was to see if I was missing something, (manifold doubles being so popular), so far I don't think I am.

My impression from your comments is that you are indeed missing a couple of points, particularly on gas management. You seem to think that the turn around point for a dive should be at half of the of the service pressure of your tank(s). I would suggest that you get familiarized with the concepts of rock bottom and rule of thirds. Either will be better than than turning around at half. And yes, it still applies even if you are soloing.

One of your points for ID superiority is that you can take 1.5 tank fulls of gas and still have a great dive. Why is it that I wouldn't be able to do the same thing with my manifolded doubles? We think of our available gas in terms of cu ft, not tank fulls. If I have enough cu ft for my gas plan I go diving irrespective of whether the tanks are half full or a third full.

 

[PfcAJ]

Ain't that part of the planning for you?

Naturally. But I also don't want to make the situation worse by losing HALF of my remaining gas just because something breaks. That's...less than ideal...

 

[flots am]

Why not?

I switched to side-mount after I thought I had blown out a couple of disks in my back.

It turned out I had only pulled a muscle, but took it as a free "wakeup call" that I was probably too old to be climbing a moving ladder with 120 pounds of steel on my back.

Now I just clip off the tanks, get back on the boat, and haul them out of the water, one at a time.

flots

 

[Jim Lapenta]

I am so close to breaking down my double lp85's and selling the bands and manifold. Since getting my sidemount cert with Doppler I am seeing less and less reason to.have anything but my lp72's doubled up. And those only for an Intro to Tech student who might want to try doubles. If I do that it'll also free up some cash as I'll have a 58lb wing and extra plate and harness to go as well. At 53 SM makes so much more sense for the dives I am likely to keep doing as well as have extra singles for those times when that's all that's needed.

Sent from my DROID X2 using Tapatalk 2