Z-system gas switching

[Kevrumbo]

Distribution block is a necessary implementation to keep the Hog long hose/Bungee'd back-up configuration --I'm comfortable with it now for at least 50 dives on Z-system doubles sidemount --with original non-isolatable distribution/manifold block-- here in Chuuk Lagoon starting last year Nov-Dec; last month 05 to 16Oct; and now 17 to 29Nov --and will be using it in Santo Vanuatu on the SS President Coolidge transport wreck 01 to 12Dec-- AND returning back here to Chuuk Lagoon 14 thru 31Dec.

(Naivete notwithstanding and my money to spend wherever tropical paradise I choose to roam --Z-system is working for me just fine). . .

 

[wedivebc]

For the life of me I can't understand why taking a completely redundant beautifully simple system like a sidemount and adding a host of islolators, manifolds and extra fittings could be considered an improvement.
The OC DIR/Hogarthian double tank system is a great, simple and highly functional system. An independent side mount system is also a very functional system. Trying to make one like the other is not an improvement on either system.

If you are diving with a sidemount team there is virtually no single failure that would require donating gas. Routing all your hoses to a central gas block puts all your eggs in one basket and causes a common failure point that now does require gas donation because any number of single failures can render a diver completely out of gas.
The concept of doing this to enable mixed teams makes no sense because side mount is designed to go places backmount can't.
This at best is a system trying to solve a problem that doesn't exist and at worst a big money grab designed to part new "tech" divers who don't know any better from their hard earned money.

 

[Kevrumbo]

There's a progression or escalation of sorts involved, but the isolator does solve the single point of failure issue that kept me from even considering the Z-system for cave diving use.

I spoke with Andrew at DEMA a couple years ago and got the impression that the Z system was originally designed to provide a means for a clean, DIR configured hose routing and back up reg for single tank monkey diving. It does that pretty well, but it obviously also had potential for two tank SM diving as well in terms of allowing a standard DIR hose configuration. The problem was that a second stage freeflow would leave you basically screwed as both regs are plumbed into the (non isolated) distribution block. To resolve that risk, you needed to:

a) add in line shut offs to each second stage, and they add 3 additional dynamic o-rings each, two of which are very prone to damage from sand and salt crystals, and damage to just one of them leaves you open to gas loss. So in effect the additional items needed to mitigate the risk creates even greater risks of their own (not a viable configuration plan); or

b) bring along a separate QD hose and second stage assembly to plug into one of your SM tanks in the event of a second stage failure - and that plan still leaves you without a wing or drysuit inflator. I can live without a wing inflator, but the lack of a DS inflator can be problematic in a cave profile where I have to descend significantly to exit the cave. And the emergency second stage assembly sucks up an entire pocket where it lives under used, often sandy and silty and with unacceptably low odds of actually working if ever needed. (Another non-viable plan.)

Consequently, the isolated distribution block resolves that single point of failure problem and now does allow a true DIR hose configuration with the isolation and redundancy needed to make the whole thing work. However the isolated Z-system still adds a degree of complexity that most SM divers just don't feel is needed. In effect it's an issue of playing the DIR tenet of a consistent hose routing on the team against the tenet of not bringing along anything you don't need to keep things simple and minimizing failure points.

That aside, the whole Z-system idea gets much more controversial again if you now decide to use the Z-system isolator manifold for technical two tank diving AND use it for your gas switches. With a gas switch using a Z-manifold and an isolator to plug in the deco gas, you've now got two tank valves and an isolator valve involved and are now using what is a very non standard gas switch protocol. Given the number of technical divers who have died due to incorrect gas switches, that's just not acceptable to me. And, even if you get past that, your deco gas system has now went from a very simple tank/first stage/second stage system to a tank/first stage/QD/manifold/second stage system.

Personally, I found that the long/short hose issue on mixed teams was much more easily resolved by just diving with a 5' hose on each tank and thus passed on the Z-system concept. However if I dove it, I'd use a standard stage/deco bottle configuration rather than try to plug it into the Z-system.

I'm in agreement with DA, the addition of more QC6's on the deco bottles adds unnecessary complications (but less chance of reg failure?). And even the non-isolated manifold could be best applied to single tank SM, but does keep to the scalable tennent of UTD. When I first started SM I looked at the many set ups and didn't notice a prevalent "long hose" on both tanks set up. I thought it through and realized that it made sense other than donating your known functioning reg, although it was functioning just a few psi ago. The iso manifold is just a way of diving SM doubles identical to BM doubles. For several reasons, I use individual reg sets on my deco bottles, less complex, less confusion, reduces wrong gas scenario. If you don't use an iso manifold for SM doubles, I'd also like to see a long hose on each tank. Just my 2 psi.

For the life of me I can't understand why taking a completely redundant beautifully simple system like a sidemount and adding a host of islolators, manifolds and extra fittings could be considered an improvement.
The OC DIR/Hogarthian double tank system is a great, simple and highly functional system. An independent side mount system is also a very functional system. Trying to make one like the other is not an improvement on either system.

If you are diving with a sidemount team there is virtually no single failure that would require donating gas. Routing all your hoses to a central gas block puts all your eggs in one basket and causes a common failure point that now does require gas donation because any number of single failures can render a diver completely out of gas.
The concept of doing this to enable mixed teams makes no sense because side mount is designed to go places backmount can't.
This at best is a system trying to solve a problem that doesn't exist and at worst a big money grab designed to part new "tech" divers who don't know any better from their hard earned money.

Z-system integrates perfectly with my mixed team of SE Asia/Indo-Pacific Wreck Divers; we use scooters to help get down in current on the deep WWII wrecks in the South China Sea (as well as getting out of the way of the big container ships in the busy shipping lanes to Singapore) --another one of the reasons why I went with the Z-system SM is that you always breath the long hose primary in nominal situations, exactly as I was taught in
Fundamentals and the configuration I am most comfortable with to this day. All I have to do when alternating tanks is turn one on and shut down the other --all easily done on-the-fly & on-the-trigger while scootering in open water at depth. i.e. --I don't have to swap/deploy/stow/clip-off regulators if I went with a traditional/conventional independent SM set-up.

So yeah, I've given it a lot of thought and understand the mechanics & contingencies of the distribution block connections: Z-system conveniently applies to my type of diving. . .

(Don't use drysuit either --skinsuit in 29deg C tropical waters is a luxury I prefer. . .)

 

[DA Aquamaster]

Kev,

I'm fine with the isolated Z-system in terms of it now being fully redundant and not prone to the single point of failure issues I felt were there two years ago when we first spoke with Andrew at DEMA about it. It's done a superb job of developing the initial concept and then also taking what was a single tank monkey diving system and scaling it to two tank sidemount technical diving. I'm very impressed by that and I admire his vision and creativity in doing that.

And, I still like what I liked about the concept in the beginning - the ability for a backmount diver familiar with DIR hose routing to transition to the same basic approach in sidemount.

However, over the course of the same two years, Marci and I resolved the "what happens when you're breathing the short hose" donation issue if diving on a mixed team by just using a 5' hose on each tank. We've found a sidemounted 5' hose is enough for us to exit through a tight restriction in trail and it is still cleanly stored in just one loop on the tank and is easily adjusted in terms of the length from tank to hose. That achieves the same "always on the long hose" goal as the Z-system, but it does it in a much simpler manner.

The short version is that, provided the Z-system has the isolator, I have zero issues diving with someone using that system in a cave, as the potential for total gas loss has been resolved - but I just don't see it as the approach I choose to take, in part due to the complexity and in part due to the rather insane amount of money UTD wants for the system.

I actually really wanted to like the system after talking with Andrew at DEMA. The system was in the $1200 range for all the pieces I'd have needed then (if I could have found a work around for the single point of failure issue) and now at the current package price with the isolator manifold it's $1,680 (actually $1,740 with the travel bands on the tanks that I'd want). In comparison, my SMS 50 cost me $450 and 5' hoses cost me about $35 each, for a total of $520. I'm enough of a gear whore to pay $500 to experiment with something I could always sell off later at only a $100-$200 loss if I don't like it, but $1,680 is well over the amount I'd risk to futz with a new system.

I do however feel pretty strongly that the ability to accommodate an air share with a long hose is an important aspect of sidemount configuration as long as there is any potential to have to share gas, such as diving on a mixed team.

-----

Dave,

I think we agree on most points in principle, if not perhaps to the same degree. The major difference in what I'm saying I think is that now and then Marci and I do find ourselves diving with 1 or 2 backmount divers in a mixed team, or alternatively as a sidemount team of two in close proximity to a backmount team of two, that we'd support in an emergency, and thus we see the value in being able to accommodate a long hose gas share.

IMHO the 5' hose is a small concession, and in fact I like the ability to just slide the hose in our out of the hose retainers to adjust the hose length feeding the reg in use at the moment, as it eliminates any excess hose that might otherwise hang away from me.

 

[decompression]

I love hearing all sides discussing a piece of equipment or protocol. Properly viewed it can greatly assist in making diving safer/more fun. I understand the z systems place in UTD, it fits in that its scaleable and consistent. I am a follower of Jeff and Andrew and they've encouraged me (and all divers) to question and think things through. Many wont adopt an isolated manifold for side mount. Having dove independent BM doubles I saw the benefit of an iso manifold and incorporated that into my diving. I view the z manifold the same way, it has wide scale applications that work within the entire UTD system. I know the debate will continue, after, can we go diving?

 

[Mitchell Teeters]

Funny, I brought this up a while back and was poo pooed on for being a crappy diver because I wanted to reduce the task loading while diving. Interesting.


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[JamesK]

I don't see how the isolator reduces task loading. I don't have to worry about shutting down tanks when I switch. I just switch. I get it, the z system does not need switching, however, I can switch as quick as someone can shut down one valve and open another.

Kev, we get it. You are diving Chuuk. You remind us every thread. It works for you there. Here in the North Florida Caves, it doesn't work for me.

I can see benefits of the system, and what AG and crew are trying to achieve. I jut don't think it out weighs the benefits of a simple dual 5' hose side mount system.

I want to see one in person, and I would like to dive it. One of my concerns is having the isolator on my back and it getting hung up somewhere crawling through low tight areas.

 

[wedivebc]

Ok so I'm still trying to figure out what this system brings to the table. Kev has told us it's better cause he likes diving it in Chuuk and DA has told us he likes it because he dives in mixed teams and wants a long hose to share and more gas I guess. He also mentioned that since the addition of the isolator he feels the system is less dangerous.
What I haven't heard is what advantage justifies the added complexity, added failure points and expense over a conventional independent sidemount system? It has to more than not switching regs, surely?

 

[decompression]

Looks cool?

 

[JamesK]

Looks cool?

Lol. It kinda does.