Double Tank Manifolds, Bad Idea!

[Tortuga68]

You still don't get it?

I get it... you can lose all your gas in manifolded doubles - if you have a failure of some sort & don't close any valves.

That's like saying your car will crash if you don't step on the brake pedal.

 

[DevonDiver]

Manifolds require training and practice. The equipment, without the skills, is more prone to critical failure. The training mitigates risk sufficiently to allow the benefits to be realized. In certain advanced diving scenarios, particularly overhead environments, those benefits are considered crucial.

In contrast, independent doubles require less critical protocols. Gas management and reg switching are all that is needed. There is less demand for training and protocols. This makes them potentially more useful to intermediate level divers in open water environments.

 

[PT4476]

This thread is becoming a poor version of Mony Pythons 'Argumnet Clinic', entertaining but not nearly as entertaining as the original version…

 

[boulderjohn]

Some of the positions taken by people in this thread remind me of the argument some people make regarding "failure points," which are too be avoided at all costs. Well, everything is a potential failure point. The only way to avoid failure points is to stay in bed, in which case you risk bed sores. People should not simply dismiss something as a failure point without considering its full characteristics.

We have to balance the benefit the item being considered, the consequences of losing it during a dive, the ability to deal with its loss, and the likelihood that it will fail. Even the simple webbing harness on a Hogarthian setup is a potential failure point, with a likelihood of failure approaching zero. Having a backplate with a harness and wing, all potential failures, beats the heck out of carrying tanks under your arm, so the great benefit totally outweighs the potential for failure.

Similarly, some people in this thread seem to be thinking as if every possibility is equal in value, as if adding up the number of pros and cons (with each pro and con being either totally pro or totally con) will yield a usable value.

 

[ianr33]

Manifolded Doubles = Dinosaur.

Independent Doubles = Stroke.

Sidemount = Cool.

 

[nimoh]

Manifolded Doubles = Dinosaur.

Independent Doubles = Stroke.

Sidemount = Cool.

That is very constructive. Thanks for clearing everything up.

 

[PfcAJ]

Why is it that I never see the sidemount config. criticized for not being able to access all the divers air after a reg malfunctions, only the ID's? Is there some magic I'm not aware of that allows a diver access to all remaining air in the sidemount config after reg failure?

Could it be that SM is the latest and the greatest and new gear to sell? And wasn't side mount started for cave diving? Seems a little odd to me since a diver can't access all remaining gas after a reg malfunction with side mount.

I make that criticism as a matter of course in these discussions.

A lot of the talk of 'feathering valves' and 'swapping regs underwater' is great for the pool, but it really loses its appeal when its game day (deep, dark, silty, on the line, with a primary light, etc etc). A REAL freeflow on a reg drains your tank in a matter of like a minute. Even if you had a full tank (you probably wont), feathering it only buys you a handful of breaths. And a breath-hold while swapping regs is pretty outrageous. Putting a lot off eggs into one basket with that little maneuver.

 

[ianr33]

I dive sidemount pretty much exclusively these days.Sidemount is functionally the same as independent doubles. It works for my diving. It is not the best for other types of diving.

Sometimes I dive solo. Sometimes I dive solo in a cave. With proper gas planning the (somewhat likely) loss of half my gas is just an inconvenience. The (rather unlikely) loss of all gas from manifold failure would absolutely kill me. More likely than a manifold faliure would be failure to isolate/shutdown quickly and correctly in a zero viz/tight/stressful situation. That will kill me as well.

I doubt many informed divers would solo overheads with JUST a pair of manifolded doubles.

 

[AfterDark]

If you really wanted to and had a 3rd tank to breathe off for a minute or two, you could swap regs underwater, although it would require service later.

If I really needed to and had a 3rd reg I could doff the IDs and change regs.

---------- Post added September 24th, 2013 at 03:58 PM ----------

The advantage of sidemount is that, if your problem lies in the regulator, you can feather a valve and still have access to the gas in that tank, which is not really very feasible if the valve is on your back. Obviously, a tank neck o-ring or valve problem can lose you all the gas in one tank, but that's true with sidemount, IDs, or MDs.

The big reason for having the tanks on your back is that they are connected to one another, and it's hard to do that any other way. If you aren't going to connect them, having them where you can't reach the valves easily just seems like an odd choice.

If I really needed to I could doff the ID's put my arms thru the straps of the harness making them chest mount and feather the valves.

---------- Post added September 24th, 2013 at 04:02 PM ----------

I make that criticism as a matter of course in these discussions.

A lot of the talk of 'feathering valves' and 'swapping regs underwater' is great for the pool, but it really loses its appeal when its game day (deep, dark, silty, on the line, with a primary light, etc etc). A REAL freeflow on a reg drains your tank in a matter of like a minute. Even if you had a full tank (you probably wont), feathering it only buys you a handful of breaths. And a breath-hold while swapping regs is pretty outrageous. Putting a lot off eggs into one basket with that little maneuver.

All that beats dying. I'll do what ever I need to do to surface short of killing innocent people. So what may seem very unlikely becomes what must be. I haven't survived all these years of diving without being resourceful. There aren't many old bold divers out there, I consider my lucky and have been down thru the years. I don't relay on it but it sure is sweet when it happens!

Off topic, my dive was pretty good, had about 15' vis that dropped to 3' in deeper water. I saved a striped bass. It was laying belly up on the bottom but its gills were moving. I grabbed it's tail dragged it backwards in a circle and let it go zoooom gone! My good deed as a steward. Good thing for him I don't eat fish!

2hrs bottom time 2.5 total 35fsw max avg 20fsw temp 65f vis 15'-3' used my 50cuft IDs consumed 4000psi of 21%.

Here's a picture of the bass I helped. There was a lot of something suspended in the water I think whatever caused it lowered the O2 levels in the area and affected the large fish like this one.

 

[PfcAJ]

Ill breath the fart out of a donkeys ass if it means not drowning. My point is that those last ditch plans aren't really practical and can't be relied on.