... what makes you think the UTD system is DIR? Whatever the merits (or demerits) of the manifold may be, I think it violates at least the basic principle of simplicity and reducing failure points that is fundamental to a DIR approach ...
... Bob (Grateful Diver)
Bob
To be perfectly clear the Z-System is
NOT DIR and was never sold that way. A little history will shed some light on this.
Hogarthian was a minimalist approach to a gear configuration in the early 90's but those that followed still kept an ideology of "each diver" should configure their own way. DIR built upon the Hogarthian concept with the approach of Standardization (late 90's till now) - mainly because of a large scale projects such as Wakulla. However, this rigid standardization in itself lead to a narrowing of the available "tool set" as it was designed for open-circuit back-mounted doubles with stages and deco bottles. Any deviation from that configuration such as single tank, side-mount or rebreather, was either excluded or "cobbled" together.
In 2007, UTD decided to take a unique direction, our roots for the previous 13 years were in Hogarthian & DIR, but I wanted to build upon that and evolve it to the next generation. Unification. I wanted to keep our tool of open-circuit back-mount (DIR) but increase the "tool set", venturing into side-mount and CCR. My mission and goal was to unify these three systems (configurations) into one system. I wanted to drive this industry forward, by keeping the mimilist approach (Hogarthian) and standardization (DIR) however I wanted to create a unified approach to the three systems, thus expanding the tool bag from exclusively back-mount open-circuit to Side-Mount and CCR rebreathers. Keep in mind that I needed to do this while maintaining consistency, scalablity and interchangability. This are some of the core elements in our 10 convenants.
UTD's 10 Covenants - Unified Team Diving
Now the Z-distribution block may make no sense to you as you may simply dive recreationally with two cylinders in side-mount format and you may not need a consistency, scalable and interchangeable approach, however in UTD it is imperative that we keep to our 10 covenants and most importantly allow for "mixed" team diving. The Z-Side-mount system uses the ideology of being consistent yet scalable between single tank, double tank, multiple tank and/or rebreather. This is something that a traditional Side-Mount configuration does not do. We keep the components of the system interchangeable, so you can use your backplate, harness, wing, light, argon bottle and so on between all the systems (back,side,rb).We even have our wings/trim devices designed that you can easily switch between back-mount, side-mount and rebreather (Delta). These are important things to us.
The addition of the Z-distribution block gives us the above mentioned advantage with "less" risk or disadvantage than an isolator knob on a set of doubles. Unlike back mount doubles which relies on the isolator knob, we do not rely on the Z-manifold, it is simply there to provide us with the ability to have long hose, necklace, bcd, drysuit, diluent and inputs. If it was to fail, our first line of defense is traditional side-mount (independent doubles) and if that has failed then our second line of defense is our UTD/DIR/Hogarthian teammate. This is an additional line of defense from traditional DIR back-mount as if you lost your isolator knob and were unable to shut down the isolator knob you only line of defense is your teammate, as you would loose all your gas.
However, all this banter about "failure" points, detracts from the core and central issue, which is, if you want a system that is consistent with your previous, current or future Hogarthian/DIR/UTD training and skills, that is scalable from single tank to mCCR rebreather, that is capable of mixed team diving, that has interchangeable components and that also allows you to configure and dive a configuration that is best suited for your diving or exploration needs, then the Z-System is the only one that is capable of that.
Andrew