Quiz - Equipment - J-Valve

[tursiops]

And that air is held back once the pressure approaches 300 psi. Is that not correct?

The air is not held back until the lever is put into the upward position; the lever was down for filling. It is not the 300 psi that holds the air back, it is the spring tension in the lever, which holds the air passage open so long as the tank pressure is greater than 300ish.

 

[Scuba-74]

 

[CT-Rich]

There is no such thing as “extra gas”. It’s not like finding a twenty dollar bill cleaning the couch. When you go in the water you have X amount of gas. Whether it is in your primary or a pony or side mount, whether it is time you switch to another air source or not.

With the J-valve, it was just like switching to the pony because you have no gauge. If you don’t need it, you don’t use it. The only reason a light goes on when you are almost out of gas is to draw attention to the fact you are almost out of gas. Thinking of the extra gas in your car or your pony or from the J-valve as a”reserve” is just an way of thinking about it as gas beyond your original dive plan. I got the question wrong and l don’t think it was as failure of understanding how a J-valve works or how gas planning works.

 

[tech_diver]

When I had to learn the difference between a J valve and a K valve, I was taught to remember K for 'killer.' The K valve had no 'alert' system (before SPGs) so it was the 'killer' valve.

 

[TMHeimer]

There is no such thing as “extra gas”. It’s not like finding a twenty dollar bill cleaning the couch. When you go in the water you have X amount of gas. Whether it is in your primary or a pony or side mount, whether it is time you switch to another air source or not.

With the J-valve, it was just like switching to the pony because you have no gauge. If you don’t need it, you don’t use it. The only reason a light goes on when you are almost out of gas is to draw attention to the fact you are almost out of gas. Thinking of the extra gas in your car or your pony or from the J-valve as a”reserve” is just an way of thinking about it as gas beyond your original dive plan. I got the question wrong and l don’t think it was as failure of understanding how a J-valve works or how gas planning works.

Agree with your last sentence. Maybe yes or no regarding your definition of "extra" gas. We know what it is, what the gas is in a pony, so what does it matter if we call it extra or reserve? I have extra clarinet pads in my case in case I need one, just like extra o rings. I know they're there. Is it wrong to label them "extra"? I don't plan on using them, so like the pony & J valve reserve, they can be called extra.

 

[Daebado]

..... It is like carrying an 8 cuft pony that you fill from your 80 cuft tank before the dive...so your main tank is now only 72 cuft.

This is the best explanation I have read so far. You want extra? Get a pony and fill it from the shop compressor.
You now have extra as compared to what your original tank can hold. Of course, as some have pointed out, you really don't have ANY extra air during a dive... you only have what you started with no matter how you configure it. You could bring along 8 pony's along with your main tank and you still don't have extra. You have exactly what you started the dive with!
Same goes for low fuel lights on cars or reserve switches on motorcycles. They don't give you "extra" fuel... they alert you to the fact that you are low compared to the amount you started with.

at least that's how I see it.

 

[TMHeimer]

This is the best explanation I have read so far. You want extra? Get a pony and fill it from the shop compressor.
You now have extra as compared to what your original tank can hold. Of course, as some have pointed out, you really don't have ANY extra air during a dive... you only have what you started with no matter how you configure it. You could bring along 8 pony's along with your main tank and you still don't have extra. You have exactly what you started the dive with!
Same goes for low fuel lights on cars or reserve switches on motorcycles. They don't give you "extra" fuel... they alert you to the fact that you are low compared to the amount you started with.

at least that's how I see it.

But does that only hold true for gas, liquid, fuel, etc.? I'm BBQing steaks and not sure if two more people will show up. So, I put on a couple of "extra" steaks. Is it OK to call them extra? They were in the freezer with the first 6 I took out and I knew they were there. Or should I call them "reserve" steaks, like with reserve air?

 

[wetb4igetinthewater]

But does that only hold true for gas, liquid, fuel, etc.? I'm BBQing steaks and not sure if two more people will show up. So, I put on a couple of "extra" steaks. Is it OK to call them extra? They were in the freezer with the first 6 I took out and I knew they were there. Or should I call them "reserve" steaks, like with reserve air?

I think your BBQ analogy is better is if you pull out 4 steaks for the 4 people that you know will attend (including yourself). Because two more people will show up, you cut two pieces off two of the steaks and set that aside for them.

 

[TMHeimer]

I think your BBQ analogy is better is if you pull out 4 steaks for the 4 people that you know will attend (including yourself). Because two more people will show up, you cut two pieces off two of the steaks and set that aside for them.

I see what you're saying. In your case those two pieces cut off would not be called extra (at least I wouldn't call them extra). That seems to line up well with reserve air when you open the J valve. Both the cut steak and reserve J valve air are/were part of the whole. But not so much with the air that's in a pony bottle since the pony is separate to begin with (like my 2 "extra" steaks from the freezer). Yet it has been also argued that a pony bottle (or 8 of them) can't be called "extra"....

But back to the 2 pieces of steak you cut off because those 2 extra people showed up--- It was intended that these pieces would remain part of the 4 steaks and would be eaten whether the 2 extra people showed up or not. The J Valve reserve air is not intended to be used--not part of the dive plan, even though it's in the same tank. So I would say it could be called extra.

In the test question answer C, you could substitute "reserve" for "extra" and I would think the voting wouldn't change due to the confusion. Reserve and extra may not be exactly synonyms, but close enough.

 

[tursiops]

The J Valve reserve air is not intended to be used--not part of the dive plan, even though it's in the same tank.

But is IS intended to be used. It is the gas you use to ascend. You dive until you can't get any gas, pull the rod, ascend.