Playing with the Z-system

To my pleasure, I got a phone call the other day from Brian Wiederspan, informing me that Jeff Seckendorff was going to come up for the Essentials class at the Aquarium, and would be bringing a couple of Z-system rigs with him. Did Peter and I, Brian asked, want to join Jeff in the pool to play with the rigs? The answer was obvious . . . So yesterday, through the graciousness of the Seattle Underwater Sports store (which allowed us to use their pool), we got to spend a half hour or so seeing in real life what this system is all about. We shot some photos and video, some of which I'll link in here, and Brian took a bunch more, so I hope he'll add.

My first impression was to be delighted with how compact the system is. The harness, wing, block and second stages all folded up into a bag about the size of a reg bag, but perhaps three times as deep. Jeff got three of these bags into a standard roller duffle.

My next impression was to be daunted by how all the straps and hoses had managed to rat's nest themselves inside the bag . . . I poked and prodded at the thing for a couple of minutes, but then Jeff came over, did a magic trick, and presto! it was all sorted out.

We then spent some time adjusting the harness for each of us. It didn't take very long for Peter, but as usual, dive gear just isn't designed for hobbits, and it took a lot more tinkering for me. In the end, it just wasn't possible to make it perfect, and I did see with interest that, having shortened the back strap as much as we did made the wing bow out away from my back in the water. Of course, as Jeff pointed out, all the components CAN be customized, if it's one's own setup.

I went and changed, and came back and shrugged into the harness. It was quite a bit tighter than I run my standard harness, and a bit of a pain to get in and out of, but again, that's something that would just take tweaking. It is SO nice to put on the harness and regs, without the weight of a tank! Since we were diving the monkey-diving version of the rig, we had 5' hoses, and I found out that a 5' hose fits me perfectly (I'd never used one before).

We went through the use of the QC, and the modifications they have made to ensure that they cannot come undone inadvertently. I have no concerns about the QC connections; they are commonly used for rebreather drive bottles, and if they're good enough for those guys, they're way good enough for me. Mine was easy to disconnect, but a bit more difficult to connect while pressurized, which is kind of important for managing certain possible malfunctions (more about that later).

I tossed my tank in the water (not exactly, out of respect for the pool surfaces, but you get the idea) and comfortably climbed down the ladder and into the water. Hooking the tank on was exactly the same as donning a stage, except for pulling the bungie forward and over the valve knob, which wasn't difficult, even with my arthritic thumbs. I got the QC connected without too much difficulty (need stronger pectoral muscles!), and filled the wing. Floating at the surface was very similar to doing so in the Nomad -- the wing held me up very well, but I did have to lie back on it to avoid going forward. I don't mind that.

In the water, the rig felt very stable and familiar and comfortable, as it ought. I was a bit baffled by searching for the inflator, which was too long (but again, in my own rig, this would be changed). The tank was initially very sloppy, but I wrapped the rear clip around the handle, which snugged it up quite a bit (and Peter did the same).

I played around for a bit with the single tank on, as you can see. But I'm not a big monkey diver, because I just don't like being unbalanced that way, so I requested a second tank, just to clip on to see what it would feel like.

It was immediately MUCH better. I had the same fore and aft stability I had liked so much with my prior sidemount sampling, although the tanks were a bit more mobile than the setup I had used before. This didn't surprise me, because these tanks were stage-rigged, and it's my understanding from my reading that, if you want sidemount tanks to be PERFECT, you will probably have to move the bands around until you find just the right place for them.

More play ensued. I found it very easy to vent the wing through the inflator -- I completely forgot to try the rear dump, to see how it would work. I could swim on my side:

and on my back. It all worked really well!

We had such a short window of opportunity, we didn't get to do some of the things we had planned, like air-sharing, but judging from the flow through the block, I don't think it would be an issue.

I spent quite a bit of time talking to Jeff about using the system as a double-tank sidemount setup. I raised the IP question, and he acknowledged that it is an issue, and right now, they are dealing with it by only opening one tank at a time. Initially, it bothered me to think that I'd be swimming around with one of my tanks turned off, but then I realized I swim around with my stages turned off, anyway. However, it does negate the advantage of a manifold, which is being able to access both of your tanks at once.

In the event of a blown hose or disconnection behind you, the strategy would be to disconnect the QC and put a spare 2nd stage on it. Of course, if you're monkey diving, you do just what you would do with a single tank, and go to your buddy for gas . . . which the Z-system makes easily possible, since each of you has a standard long-hose/bungied backup regulator setup. In a cave, especially in a restriction, the idea of fumbling in my pocket for a second stage, and then trying to shove it onto the QC, all the while possibly without anything to breathe, was worrisome.

But the thing that bothered me the most, thinking about it last night, is that, by hooking both regulators up to a single gas source, you've basically lost the redundancy that either a manifold or independent sidemount doubles gives you. This is because the only solution to a major leak anywhere in the system (at least beyond the first stages) is to shut the gas supply to BOTH regulators down.

So I think I came away with several conclusions: The setup is a nice way to allow monkey diving and enable the divers to share gas, without any convoluted hose setups. The harness and wing have a lot of potential as a sidemount setup (probably work great right now with Al80s in warm water, and wouldn't take a whole lot to scale up to cooler water/bigger tanks). But I don't see the block working, for me, in its current form, for technical or overhead diving, because of the loss of redundancy.

Thank you so much, Jeff, for bringing the equipment for us to try. And again, a big thank you to Underwater Sports, for their generous hospitality!

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Comment by Lynne Flaherty on January 18, 2011 at 4:39pm: Yes, the harness and wing are REALLY comfortable and functional (and familiar)!

Comment by Marc Blackwood on January 18, 2011 at 3:46pm: Nice writeup, Lynne. It's good to see someone who doesn't monkey sidemount regularly get right into it (fit issues aside) and have it be functional.

Comment by Lynne Flaherty on January 18, 2011 at 7:39am: Thank you for your response, Andrew! I definitely agree that the isolator is also a potential loss of redundancy (which is why Jeff Bozanic has written essays proposing that we shouldn't use them). And I also agree that the block itself just isn't going to fail. But it still troubles me that a free-flowing regulator means having to disconnect both QCs, and if you are not diving with a hose and second stage on each tank, pulling a spare reg out and trying to get it on the QC while patiently sitting there not breathing :-) Sidemount cave, of course, being exactly the kind of place where it is by far the most difficult to establish air-sharing . . .

At any rate, all I'll say now is that we'll watch the evolution with interest. And I'd sure love to get back to the Red Sea!

Comment by Unified Team Diving on January 18, 2011 at 2:51am: Lynn

Firstly, thank you very much for taking the time to come out and try the Z-System. I very much appreciate people who take the time to try, learn and actually use something new prior to simply going out on to the internet and typing their negative poh poh'ing of a new concept - in their "IMHO's" of course :). Secondly, I apologize for the tardiness of my response as I am heavily involved in conducting a very intense Korean IDC and it has being all consuming. As you can imagine, it is hard enough to cover all the UTD materials, S&P, play book, philosophy, teaching principles and other concepts in english to english speaking instructor candidates, let alone having to pause every sentence, while my words are being translated into Korean, however things are going fantastic and this is gonna be a very successful three week of IDC training.

As far as your comment- " But the thing that bothered me the most, thinking about it last night, is that, by hooking both regulators up to a single gas source, you've basically lost the redundancy that either a manifold or independent sidemount doubles gives you. This is because the only solution to a major leak anywhere in the system (at least beyond the first stages) is to shut the gas supply to BOTH regulators down."

I wanted to reply to you by having you consider that as far as a traditional "Manifold" is concerned, first of all, they are High Pressure Connections between two cylinders and there is no "true" isolator. The supposed "isolator" is actually a std tank valve turned on it's side. That means there is a Tank Valve Knob, connected to a stem, connected to a high pressure seat, that is located inside an o-ring sealed high pressurized chamber. This high pressure seat can then be twisted up or down onto a Knife Edge that is inside of this chamber and is part of the connection to the right tank -generally. The left tank is connected to a small opening that also house in this chamber. Of course, the stem of the valve knob must pass through the center of the chamber and a nut that seals this chamber.Therefore the stem must also be o-ring sealed. The isolator knob then protrudes 5-7 inches off the back of our tanks and is much much more exposed than a z-manifold. Now, "if" one was to smash this manifold isolator knob and damage it or compromise the stem or knob or hp seat - depending on what happens - two outcomes are inevitable. If you are still able to shut down the isolator knob, then you will only lose the left tank. If you are unable to shutdown the isolator knob you will certainly lose both tanks and therefore all regulators and redundancy..that you propose "double tanks" have. Therefore by your above argument diving an isolator on a manifold should also trouble you as compromising the isolator knob will definitely cause a loss of all gas and redundancy of the regualtors. However in Hofgarthian and the DIR and now UTD configuration we have long ago felt that the risk of loss of this isolator knob outweighed the benefit and therefore we chose Isolatable manifolds rather than the non isolated manifold that we dove in the early 90's.

As a side note, I have seen this happen to a buddy team on a real dive and yes the diver slammed the ceiling and proceeded to lose ALL gas and therefore redundant regulators - they simply went into an air sharing scenarios and exited with their team mates.

As far as redundancy that you state that "independent side mount tanks" provides, we actually do have that built into the Z-System, when technical or cave side mount diving, we require a redundant second stage regulator on each stage/deco tank OR a backup regulator in your pocket that is attachable via QC6 Female onto the male QC6 LP on all stages and deco bottles. Therefore we actually do have redundant regulators and access to that gas if the Z-Manifold was to fail.

Now, what is the reality of a low pressure, distribution block, with static o-rings, laying 1"inch off your back from really failing? ....Just not gonna happen and even if you were to sya 1 in a billion then this low low risk is by far overshadowed by the benefits this distribution block gives us when it comes to being consistent within our community, environment, training and skill set, let alone the the scalability of this system to tech/cave/rebreather and so on. Independent double side mount tanks just defy every Hogarthian/DIR/UTD principle we have, never mind the hassles of air sharing, minimal configuration, unified team diving approach and so on. In the future the consistency, scalability and reliability of the Z-System will become evident, as I slowly release each part of the configuration along with the education. You will see Z-system is an excellent way to dive for people who want to side mount - or even back mount - with a single tank, technical/trimix diving, regular cave diving , "true side mount needed" cave diving, PSCR, MCCR and so on. The future is so exciting. Just simply plug in the gas you need for each part of the dive. Bottom, deco and so on :)

I truly hope this helps to explain more about the Z-Manifold, the system and so of your concerns and hopefully we will get a chance to dive again, enjoying places like the Red Sea.

As always, Safe Diving
Andrew