Distribution block question.....

[amascuba]

amascuba ... That's a pretty convoluted solution ... and one that may not be practical or achievable in a tight hole.

... Bob (Grateful Diver)

Of course, and I've been agreeing all along that I don't think that the z system is the best solution for being in a tiny hole.

 

[amascuba]

So here's where we disagree:
-I don't consider either "onboard" redundancy or self-rescue to be optional in any technical environment.

So, in a gas loss situation (with backmount doubles, deco/stage, or an inflation system) you don't do ANYTHING except let your team mates fix the problem for you?

In a maskless situation, you don't attempt to deploy a backup or attempt to signal team mates?

In a run away inflator scenario, you just let your wing or drysuit inflate to the point to where it rockets you to the surface?


Of course you're going to respond to those situations(I hope!) with some sort of self rescue! Yes we dive in a team environment and our team mates are our ultimate backup, but we have to do a lot of the rescue ourselves and then get our team mates involved when it's necessary - such as literally being the eyes behind our head in gas loss situations involving backmount doubles.

-There's little point in messing with a time tested configuration (backmount doubles) unless the new configuration offers clear benefits. For sidemount, it does in specific environments (sidemount caves, and to save weight on the back in environments where tanks can be staged). Why design a sidemount system that has two major flaws for its primary use? Should we now have to learn four systems (backmount, z-system, sidemount, CCR) for their appropriate environments? Viewed that way, the range of environments where the Z-system is ideal looks pretty slim.

That's really for you and your team to decide. Right now, I'd primarily use it for tropical trips, deeper open water recreational stuff, and potentially in some overhead environments while traveling. I don't think I'd use it in tight overhead environments that getting team mates to respond to emergencies would be slow at best.

 

[SuPrBuGmAn]

Bubbling doesn't automatically mean a failed regulator.

You're correct, however, the answer isn't to default to your buddies gas at the first sign of trouble. You seem to agree with that below.

Y

ou don't automatically swap second stages on manifolded doubles. In manifolded doubles, if you hear bubbling behind your head, your first quick move is to determine which side is bubbling and shut down that side. If you are unable to determine quickly, default to the right side, breath down the second stage, swap to the necklace, and listen for bubbles. If they haven't stopped, then isolate and call a buddy to look at the problem. At this point it could mean a few different situations - left bubbling mistaken for right, left/right isolator, protruded neck o-ring, or something like needing to reseat a DIN o-ring.

In typical sidemount configuration(non convoluted Zsystem), there is no mistaking which side will be bubbling. You shut down the valve to the tank which has a problem, breath off the good regulator, call your dive and move along with life.

Basically, all you're doing is treating the z systems manifold like manifolded doubles, with two exceptions; (1)Instead of using an isolator knob to isolate the tanks in a gas loss situation, you disconnect the tanks from the manifold and (2)One tank turned on at a time and using sidemount gas strategies to evenly consume gases from the tanks. At the point where you need to isolate the tanks, you will require a stage rigged second stage or a QC6 rigged second stage to continue breathing from the tanks. Of course, traditional sidemount rigging is simpler, as are manifolded doubles in a situation where you're dealing with a gas loss situation. However, with practice, I believe that a competent diver can handle easily handle the situation.

All the downsides of a manifold, without any (true)benefit, along with a lengthier process to get working gas to yourself if there's a problem.

EDIT: You still have the option of swapping to your necklace if your primary stops delivering gas. You also have the option of using a different second stage by turning one tank on and the other off. Most everybody that I know uses downstream second stages, so instead of not working, they typically fail open and bubble, so with that in mind, if your primary stops working it's usually because you're out of gas and would need a donation regardless (with manifolded doubles and z system sidemount - unless you had a roll off while breathing your necklace on backmount doubles)

You're still introducing additional steps to get yourself gas in either option(deploy stowed 2nd stage, or hook in QD 2nd stage) and cranking the valve open; or cranking one valve open and shutting the other off(assuming its not a gas block problem thats the cause of concern).

 

[amascuba]

You're still introducing additional steps to get yourself gas in either option(deploy stowed 2nd stage, or hook in QD 2nd stage) and cranking the valve open; or cranking one valve open and shutting the other off(assuming its not a gas block problem thats the cause of concern).

Not necessarily. The necklace is tied into the distribution block, thus going to the necklace gives you gas from the same gas source. But again, on a downstream designed second stage, you're generally going to either be out of gas or be in a valve roll off scenario if the second stage stops delivering gas. If the second stage were to malfunction or an IP creep on the first stage were to occur, the second would free-flow gas. With a roll off, you would just turn the tank back on and if you're out of gas, then your sharing gas regardless.

In a scenario where you have a gas loss from the distribution system, the second stage will continue to work, and YES you would have to deploy a stage rigged second stage or deploy a QC6 rigged second stage and disconnect the tanks from the distribution system. It IS convoluted, but honestly, with practice, I don't think that it would be any more difficult or take any longer than dealing with a loss of gas in back mounted doubles - like a left post mistaken for right post that's unfixable.

 

[gsk3]

-I don't consider either "onboard" redundancy or self-rescue to be optional in any technical environment.​

​

So, in a gas loss situation (with backmount doubles, deco/stage, or an inflation system) you don't do ANYTHING except let your team mates fix the problem for you?

Glad we agree. Please read my sentence again.

That's really for you and your team to decide. Right now, I'd primarily use it for tropical trips, deeper open water recreational stuff, and potentially in some overhead environments while traveling. I don't think I'd use it in tight overhead environments that getting team mates to respond to emergencies would be slow at best.​

That's fine for you, but it seems like a pretty narrow range of use to me. AG seems to suggest it for narrow caves somewhere between minute 6 and 8 of this video: ​

UTD Video Equipment Blog - Z-System - Side Mount Configuration - Part 2 of 2 - YouTube

 

[amascuba]

Glad we agree. Please read my sentence again.

No matter how many times I read it, all I see is that you don't believe in self rescue in technical environments as that's what your words say.

I believe what you're really referring to was you don't believe that diving in restrictive areas where your team is slow to respond or unable to respond due to environmental variables isn't an option for you. Maybe I wasn't clear, but by onboard redundancy, I was referring to a traditional sidemount configuration. I have a lot of respect for the individuals who dive in those very tight and long passage ways and I understand very clearly that in that environment a team could be more of a hindrance than a help.

 

[rongoodman]

No matter how many times I read it, all I see is that you don't believe in self rescue in technical environments as that's what your words say.

You're reading it backwards. He's saying that onboard redundancy and self-rescue are not optional, i.e., they're required.

 

[gsk3]

You're reading it backwards. He's saying saying that onboard redundancy and self-rescue are not optional, i.e., they're required.

Precisely.

 

[DaleC]

A lot of my points have been addressed by others but I still want to know (because I am curious)...

If I have a failure with independent tanks I have two open tanks available to me to draw from and can see where the failure is occurring. I swap regs (if necessary) and shutdown, having at that point now secured a viable tank with minimum gas to exit and perhaps some in the other.

With the Z system I am diving one tank closed. If I have a failure where I can't see it, I have to disconnect one tank to add a back up reg. Can I do that on a pressurized tank (don't know with that type of disconnect)? I also have to remember which tank I am currently breathing from (because there is no visible clue to tell me) as I may either be adding a reg to a closed or live tank. How do you remember all that when the sh_t hits it (like when a distribution block O ring extrudes or the LP feed blows out right behind your ear). A Z diver would/should be prepared to do all of that blind.

I also have to decide to shut down the other tank before, or after, I take the time to disconnect/reconnect the B/U reg. If before I preserve gas but delay the retrofit; if after I swap out regs faster but lose a lot of gas. This is akin to the "which do you go to first - Isolator or post" debate.

Honest question - what's the drill?

And, are the rest of your teammates equally trained to do the same shutdown/swap drills or is the Z diver the only one with sufficient experience to do so in a stress situation. Though the equipment may be intended for universal application, the procedure is vastly different than that of a manifold drill so the team cohesion thing really doesn't jibe unless they are. Again an honest question because, as it is, I know a manifold drill well enough to help another diver but I have no clue what you do when for the Z system.

 

[billgraham]

I don't know about your cave class, but in ours, we were required to exit at the same speed or faster that we went in while sharing gas in a zero-vis scenario. If you're taking twice as long, then something is very wrong.

That's a nice concept in a class but the reality is that things always take longer, go slower and use more gas than you think when the **** hits the fan.