To double or not to double ...

[swedish diver]

I prefer the manifolded doubles to pony for several reasons. But you should know that in one sense pony implies more redundancy than doubles. If your isolator fails, and stars leaking, this could result in an OOA situation. However, I've never heard of this happening - except on people diving doubles with too large spacing for the manifold, so that only one of two o-rings are active on either attachment point of the "midsection".

Ponys eliminate this problem, but I concider them less appropriate since:

1) they are bulky
2) positioning and trim is easier with doubles
3) it's more simple "SIMPLE IS GOOD"
4) the weight is equally distributed on your back
5) the redundant air supply is larger
... plus some other reasons i cannot think of now

regards

/Kristian

 

[Goldminer]

Originally posted by swedish diver
almost

I prefer the manifolded doubles to pony for several reasons. But you should know that in one sense pony implies more redundancy than doubles. If your isolator fails, and stars leaking, this could result in an OOA situation. However, I've never heard of this happening - except on people diving doubles with too large spacing for the manifold, so that only one of two o-rings are active on either attachment point of the "midsection".
/Kristian

I accept your point that a pony provides more redundancy than twins but I was just answering the question about why H-valves are not considered redundant enough air supplies. I guess I should not have use the word total.

If one side of your isolator crossbar fails I believe that you are still redundant, you just close the crossbar valve and breath from the other side. You would need leaks on both sides or a leak from the stem of the isolation crossbar valve to have the danger of an OOA situation. As you imply unlikely but possible.

 

[Rick Murchison]

Originally posted by Goldminer
You would need leaks on both sides or a leak from the stem of the isolation crossbar valve to have the danger of an OOA situation. As you imply unlikely but possible.

Right...
Probably only about 437 times more likely than a tank o-ring failure under an "H" valve.
The objections to "H" valves are pulled out of thin air - manifolds are far more fragile.
Rick

 

[Mitch421]

I got double 104s for one reason and one reason only--so I don't have to wear a weighbelt.

All the other reasons are incidental.

As for redundancy with my manifolded doubles, I can't reach that isolator valve anyway so I take my trusty pony. While I usually prefer a buddy, I don't trust that my buddy of the day is going to know what to do with the isolator valve even if I explain it to him/her on the boat before the dive.

I know that the DIR folks believe strongly in the buddy backup system, but in the recreational world, where you are often diving with people for the first time, the buddy system is less than optimal.

I've been doing some shoulder stretching exercises daily in order to evenually be able to reach the isolator valve, but Houdini, I'm not.