Appeared in DIVER October 2006

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REGULATOR Oceanic GT3 CDX-5 DVT
WOULD YOU LIKE TO TRY THE GT3 CDX-5 DVT
I was asked recently.
Say that in English and Ill have some chance of knowing what youre asking me to try, I replied. It reminded me of the days when British cars had similar inscriptions emblazoned proudly on their boot-lids. I wonder what happened to all those TC IRS Pi SOAS cars that were built. Languishing in barns across the country, no doubt.
The man from Oceanic conceded that DVT stood for Dry Valve Technology and I forgave him the rest.
So what is DVT Its a way of being able to throw your regulator into the rinse tank without remembering to screw the dust-cap firmly in place, and will be a god-send to dive centres at holiday destinations.
Remember those signs that say that anyone who does this with a rented regulator will have to pay for a full service DVT on rented regulators will lose those dive centres another valuable source of cash flow, because it positions a little spring-loaded ball against the intake orifice. Tank pressure displaces it but otherwise it springs back to keep water out.

Call me old-fashioned
GT3 reminds me of a ridiculous sports car, the GT6. It had a big engine (TC) but cart-springs instead of IRS. It was horrid. I assume that Oceanic didnt know this when it chose this otherwise meaningless name.
The original GT was a lightweight plastic second stage devoid of knob or switches, but the GT3 is far more sophisticated.
It has a knob that allows the diver to crank up the cracking pressure if it breathes too easily and, once adjusted, its Patented Dynamic Adjustment keeps it like that throughout the dive and at any depth.
I just put it in my mouth and breathed off it. Call me old-fashioned, but if I want less air, I suck less hard.
Still, it allows the manufacturer to give added value at the point of sale. Im only surprised they didnt call it the GT3 PDA.
The regulator is made from an ABS/polycarbonate composite that makes it extremely lightweight, and air flows unobstructed into the mouth to give an easy breathe. The comfortable mouthpiece took into account the natural overbite of my jaw. Please dont call me Goofy.
Its paired with a diaphragm-style regulator first stage with built-in environmental protection, something that seems essential for the British market. We all seem daft enough to chuck ourselves into freezing dirty lakes from time to time, and the environmental kit keeps dirty water out of the mechanism, and with it any water likely to form ice crystals and gum up the works.
Free-flows that manifest themselves at the second stage are usually the result of increased intermediate pressure through a fault developing at the first stage. Of course, once the process starts its exponential, and ice will form at the second stage too, no doubt.
Oceanic should award prizes for suggestions as to what CDX-5 stands for. I guess its something like covered diaphragm times five ports. Do I get a prize No, there are two high-pressure and four mp ports.
Oceanic says: The balanced diaphragm first-stage design has been the regulator of choice for many divers who find themselves pushing the envelope, so I will just have to check with my postman. He dives too!
Oceanic gives a limited lifetime warranty on parts if you get the regulator serviced regularly, and the company sticks its neck out by promising a work of breathing (presumably at CE-certification criteria) of less than one joule. Thats up with the best weve tested.
The unit does remind me of the old Delta 3, which always did well in our side-by-side regulator comparison tests.
Cut to me using the GT3 CDX-5 under water. Doy-ing! Doy-ing! Doy-ing! The first stage proved to be disturbingly noisy. It was as if I could hear the valve opening when I inhaled and clanging shut when I stopped.
At depth, with the tank still relatively full, each inhalation ended with a sound that made my buddy sure he could hear dolphins. It did not inspire me to take it deep, although the actual amount of air available could not be faulted.
It was only after two dives that I realised that this was the Dry Valve Technology at work. I had expected the tank pressure to push the valve open and leave it that way until the regulator was disassembled from the tank.
This was obviously not the case. Im making an educated guess but I think that once the pressure at the intake of the regulator is in equilibrium with that of the tank, the plastic ball valve of the DVT unit continuously opens and shuts.
On each breath, the ball valve has to pull back to allow high-pressure air from the tank through. When I stopped inhaling, the hp gas in the space between the DVT and the regulator first-stage valve allows its compressed spring to ping back into place.
If I stopped inhaling gently, or if it had to fight a lot of tank pressure, as it did at the beginning of a dive, the spring simply sighed with a little dolphin-like squeak as it repositioned the ball valve.
An alternative analogy is that it sounded a bit like a bicycle pump on a full tyre. Once the tank pressure was reduced, it made an ominous sound like a church bell tolling.
This DVT might be great for dive centres, and the air supply could not be faulted, but those underwater sound effects simply put the wind up me.
The Oceanic GT3 with CDX-5 DVT comes nitrox-ready for up to a 40% mix. It costs £230.
li> Oceanic SW 01404 891819, www.oceanicuk.com


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- That noise!