Using back mount doubles as single tanks

[rob.mwpropane]

Burst disk, tank neck, crossbar orings, knob break off with leak.

I am aware of at least two instances of burst disks leaking in-water post ceiling contact.

Do you know if either of the burst disks had been recently serviced... or not ever?

I am aware of numerous instances of knob break offs or stem shearing rendering knob unusable. Precariously close to a situation where you can lose all your gas pretty quick.

Of the isolator or L / R valves?

Isolators require management. It is unlikely that you will need one. It is unlikely that you’ll need a long hose, too. But man if you need it, you REALLY need it.

Did you know that the founder of the WKPP and namesake of the Hogarthian system, who is still an active cave explorer, doesn't use an isolator on his doubles... he uses straight bar (this is an excerpt from another member on this forum, but I'm not sure if he wants to be dragged into this discussion so I just copy pasted).

I'm not really arguing against isolators, I like mine, I use it. Just playing devils advocate. When anyone says "this is the only way" and then I hear of guys with many moons diving saying the contrary it's a good discussion to have.

Fun fact; just this afternoon I was working on my car changing fuel injectors. Had to spin a nut in a precarious situation upside down behind the engine and low and behold... I spun it backwards a few times before I realized what I was doing. No panic, no fear, just an honest mistake. I threaded pipe for a lot of years, so this is really really uncalled for, but I'll admit I did it. I can 100% see how in a panicked diver turning the valve the wrong way can happen.

 

[Twiny]

Do you know if either of the burst disks had been recently serviced... or not ever?

Of the isolator or L / R valves?

Did you know that the founder of the WKPP and namesake of the Hogarthian system, who is still an active cave explorer, doesn't use an isolator on his doubles... he uses straight bar (this is an excerpt from another member on this forum, but I'm not sure if he wants to be dragged into this discussion so I just copy pasted).

I'm not really arguing against isolators, I like mine, I use it. Just playing devils advocate. When anyone says "this is the only way" and then I hear of guys with many moons diving saying the contrary it's a good discussion to have.

Fun fact; just this afternoon I was working on my car changing fuel injectors. Had to spin a nut in a precarious situation upside down behind the engine and low and behold... I spun it backwards a few times before I realized what I was doing. No panic, no fear, just an honest mistake. I threaded pipe for a lot of years, so this is really really uncalled for, but I'll admit I did it. I can 100% see how in a panicked diver turning the valve the wrong way can happen.

With all valves fully open or fully closed, even if narked or panicked, I do not see myself having a problem at turning them properly

 

[crofrog]

With all valves fully open or fully closed, even if narked or panicked, I do not see myself having a problem at turning them properly

If you’re so narked that you’re worried about turning valves you’re doing other things wrong

 

[Twiny]

If you’re so narked that you’re worried about turning valves you’re doing other things wrong

I said that even in the worst situation I do not see myself having problem to turn in the proper direction a fully closed or fully open valve, makes sense ?

 

[rhwestfall]

With all valves fully open or fully closed, even if narked or panicked, I do not see myself having a problem at turning them properly

Seems easy, but going through a tunnel at 145' in low vis 36 degree water and having a reg fail while performing an air share certainly makes coherent thought go sideways .

 

[Twiny]

Seems easy, but going through a tunnel at 145' in low vis 36 degree water and having a reg fail while performing an air share certainly makes coherent thought go sideways .

Yes so then better go sidemount for extreme situations

 

[BlueTrin]

There's actually been a push by some to completely do away with the isolator valve because in a lot of OOG situations the diver has been found with one tank still with gas. They either rolled it the wrong way or forgot or whatever.

That's always in the back of my mind when I splash. Always check my isolator

You should be able to tell by checking your SPG. But you can just leave it open all the time?

One student, in the same class than I was doing, actually ran out of air during the class due to a closed manifold … when we asked him if he didn’t feel that it was weird that the SPG didn’t go down … he said he thought he had a good SAC rate … that was during a dive where we had to write down our remaining gas to infer our sac rate

 

[crofrog]

You should be able to tell by checking your SPG. But you can just leave it open all the time?

One student, in the same class than I was doing, actually ran out of air during the class due to a closed manifold … when we asked him if he didn’t feel that it was weird that the SPG didn’t go down … he said he thought he had a good SAC rate … that was during a dive where we had to write down our remaining gas to infer our sac rate

The fact the instructor didn’t catch that is amazing.

 

[MarkA]

Seems easy, but going through a tunnel at 145' in low vis 36 degree water and having a reg fail while performing an air share certainly makes coherent thought go sideways .

That’s why someone in post#44 said about having 4 2nd stages

 

[Gone for diving]

Maybe we should talk about inverted doubles, with an isolator.