Double Tank Manifolds, Bad Idea!

[DaleC]

Last I heard he was diving 3 tanks manifolded together (non-isolation) with a separate tank independent. It makes sense when you are 200 odd metres down though as you loose gas pretty quick at that depth.

That was only one dive. Go to his website and look at his expedition gear.

Gabe, you are forgiven as long as one of those tanks are for me... and it's got H in it.

---------- Post added September 19th, 2013 at 07:00 AM ----------

Not that it matters to me but I am curious as to how commonplace isolation manifolds would seem to be in the collective conscientious if things had gone a little different. IRL, I see people diving a lot of different ways but the Hog system seems to get most of the press. I think this is partly because it solved a problem for cave divers and they had quite a champion (good or bad) for their "vision". That same group of cave divers then went on to create a system based on that configuration and pushed it outward to the mainstream.

ID use really doesn't have that kind of push, either from an individual or an group. People just dive it. There is no organized agenda to have them recognized as "the system", perhaps because they are used by divers who are more solitary by nature (?).

As Churchill is credited as saying: "History is written by the victor". But the victors should also be aware that theirs may be but a fleeting glory. Remember VHS vs Beta. How many people still use VHS? Looking forward, SM and RB's may one day make MD's look obsolete.

 

[boulderjohn]

OK, your right cave diving isn’t dangerous, How dare I suggest such a thing, It’s only the second most dangerous sport in the world, after BASE JUMPING.

You have apparently run into one of those phony "top ten" web sites in which someone makes a list based on absolutely nothing statistical.

Can you tell me by what objective measure you made this statement?

 

[mathauck0814]

For those of you using ID: How do you handle hoses and routing? Part of what I see as a benefit to manifolded doubles is the long/short hose configuration. Are you diving with a long/short from each post? Seems the ID solution would produce clutter.

 

[tracydr]

God's Pocket Resort here in BC has had an "elevator" in their dive boat for some time now.

God's Pocket Resort - Boat Elevator - YouTube

God's Pocket is on my Bucket List. I've watched a number of videos on the diving in that area. I also had noted the lift on their dive boat. Wish more cold water boats had those.

 

[Tortuga68]

Once you connect those two tanks together with a manifold you no longer have redundancy, you have essentially made one big tank! Any number of failures (all though rare) can loose you all your back gas

I'd still like to hear about all these failure modes. I'll start you off:

1. Catastrophic manifold failure
2. ???
3. ???

 

[tracydr]

"I didn’t realize the sensitivity many disabled divers have to being different from other divers until this project. This prompted us to eliminate the ladder entirely so all divers ride the lift while seated. Able-bodied divers have the option to jump off the stern or ride the lift up while standing but we made it a good place to finish gearing up and relax if their buddy isn’t quite ready. We only carry six divers so the speed to get in the water isn’t much of an issue."

Akimbo, I can tell you that I'm very reluctant to ask for extra help or different procedures, especially while diving. I think some of that comes from having a husband who has not fully come to terms with having a wife who is not as strong as I once was. He had a hard time at first, with me using wheelchair or crutches when we would go out to eat or shopping. I also don't want to worry the boat crew, who may then think that I'm not capable underwater, too. I think this is probably more common than most people realize. My husband is getting used to the idea of me needing help but its not easy for me to ask, especially around strangers. I don't even use the handicap parking on good days, feeling that others more "handicapped" than me should be given the space.
Plus, I've always been strong and capable. I had the highest female score on the PT test during Officer Training School, ran cross-country. i also fox-hunted, which, on an off-the-track horse, takes tremendous strength. To now need extra help with simple things like grocery shopping and chores, it's really hard. It's probably one of the hardest parts of having a disability, for me, anyway. It took me nearly two months of struggling at work, going through severe pain towards the end of the day, before I finally told them that I couldn't stand or walk between exam rooms anymore. It was a simple fix, sit-down and have patients come to you. Yet, it took me that long to finally admit I couldn't do it the " normal" way anymore.

I'm really doing a lot of research on how I can continue towards my cave/technical diving dream. I know that I'll be able to manage recreational diving, one way or another. I can easily manage donning/doffing gear in the water, though that doesn't thrill me in rough water with a drysuit, since I always seem to get caught my shoulder strap caught on my valve. I'm planning to practice a lot of donning/doffing in the water with my drysuit this winter, once I'm done recuperating from my second surgery, which is scheduled for next week. A back roll into the water and just removing the gear for exit is another possibility, at least on many boats. That would allow me to enter water without having to stand up and walk with a tank on my back.
But, tech/cave diving, with all the heavy equipment, will take some extra planning. Having dove in some pretty rough surface conditions, I don't think I would want to gear up in the water with doubles. A boat like the one you're talking about could make all the difference. Will they allow tech diving or at least practicing with tech gear in shallower waters? If you could, please PM me some details. I'm pretty excited about this, really.
I'm really looking forward to getting back in the water. We were just talking about a short, "shake-down" trip to Catalina near Christmas, to ready me for a trip with Truth Aquatics in January.

 

[mathauck0814]

It's admirable that you continue to have passion and enthusiasm for diving, but I do wonder about your goals of tech diving. If you can't, for instance, carry a set of doubles how will you manage the situation when/if your buddy has a tox event and you have to pull him out of the cave/up the stairs/etc? Or is that a risk that your dive team will have to accept (that you might not be able to and however that ends for them is ok)?

Technical diving is all about planning for the worst case scenario and evaluating the strengths and weaknesses of the dive team prior to deciding to make the dive.

I mean no offense by it, just very curious how you and your husband or others in your dive team are planning to compensate for your back?

 

[MaxBottomtime]

The first time you experience a free flowing reg is when you learn to appreciate an isolated manifold. Close the valve of the leaking reg and you still have access to all your gas.

 

[Akimbo]

The first time you experience a free flowing reg is when you learn to appreciate an isolated manifold. Close the valve of the leaking reg and you still have access to all your gas.

That is also true for the few manifolds that have post valves (regulator stop-valves) but don't have cylinder isolation valves. If your dive plan calls for aborting the dive on a regulator failure then there is no advantage over IDs. It all depends on the dive plan and the individual's acceptable risk formula. It really only becomes an issue in hard or soft overhead dive profiles.

 

[nimoh]

The OP does make some good points. If you are unable to reach your valves, or do not understand how to manipulate them when solving problem, then yes manifolded doubles are probably not a good idea.

If manifolded doubles are going to be used, then valve drills should be practiced enough that muscle memory will kick in during a stressful situation.