is the valve open?

[all4scuba05]

a) Some say to take 3 or 4 breathes from your reg. while on surface to make sure needle doesn't bounce, therefore proving valve is all the way open.

b) Some have also said that valve could let enough air through at surface but not enough once you're at depth if only partially open.

question: Does anyone know if a) proves b) won't happen?

 

[sasscuba]

Whenever I am on the boat, I open my own valve and if they DM does it before I have a chance to I double check to make sure it is open anyway. Has never failed me yet.

 

[Far_X]

Remember just how little it takes to clear the hoses when you remove the first stage from the tank? So it should be easy to equate that to taking a few breaths. Of course, you could always ask, why is it possible that you have opened your valve in the first place only to turn it off again. If you are responsible for seeting up your own equipment, make sure that the last thing you do before donning your gear is to turn on the valve and check all connections. Then you know it is on. If you get interrupted during this procedure, start the whole process again.

 

[Walter]

If you are responsible for seeting up your own equipment........

If? Of course you are responsible for setting up your own gear. You may (I don't understand why you'd want to) let someone else set it up, but the ultimate reponsibility for your gear always rests with you.

 

[all4scuba05]

Totally understand and haven't had that problem. Just want someone to clearify what's being said. Saturday, I'm going to open my valve just enough to keep the needle from fluctuating at surface. Then I'll start dropping down slowly until I reach a depth that causes the b) situation.

 

[do it easy]

(A) will only prove that the valve is not closed, for example, set up gear on boat and then turn air off during the boat ride, but forget to turn the air back on before splashing in. There will be air in the reg and hoses that will show pressure on the SPG, but a few breathes will drop the needle to 0. If the valve is only partially open, the needle may not bounce that much if at all. This will lead to (B)

(B) could happen and has happened to a few people around here.

Personally, I do check my pressure before I jump in, but if I want to check the valves, I check them directly by TOUCHING them and TURNING them. Watching the SPG only checks the valves indirectly, and may not correctly indicate whether the vavle is fully open or not.

Also, once I put my regs on a tank, I don't turn the air off, although I understand that some people check for leaks this way. I do this in my garage, but I also own my own stuff and don't rely on rentals.

 

[Walter]

(A) will only prove that the valve is not closed,)

You are mistaken. If the valve is on, but not on far, the needle will drop when you inhale, then rise when you exhale.

for example, set up gear on boat and then turn air off during the boat ride, but forget to turn the air back on before splashing in. There will be air in the reg and hoses that will show pressure on the SPG, but a few breathes will drop the needle to 0. If the valve is only partially open, the needle may not bounce that much if at all. This will lead to (B)

This part is correct.

 

[cerich]

a) Some say to take 3 or 4 breathes from your reg. while on surface to make sure needle doesn't bounce, therefore proving valve is all the way open.

b) Some have also said that valve could let enough air through at surface but not enough once you're at depth if only partially open.

question: Does anyone know if a) proves b) won't happen?

In conjunction with actually checking the valve is open first.

It is possible to have it open yet the flow still restricted thus the "a" part of your post.

 

[wedivebc]

I can reach the valve of a single tank so I have messed with them before. On a fairly new thermo valve I turned it in at about 70ft until my spg started bouncing then ascended. By 30ft the spg was hardly noticable unless I took a really hard breath.
Try it. Make sure you can reach the valve though and let your buddy know what you are up to.

 

[MikeFerrara]

You are mistaken. If the valve is on, but not on far, the needle will drop when you inhale, then rise when you exhale.



This part is correct.

Walter, I have seen valves that were not open all the way and the needle not bounce until at depth where "a breath" required greater flow.

I wouldn't count on breathing while watching the needle to tell me much at the surface. I reach back and check my valve or valves in the water on every dive. I want to know that it's open all the way and not just far enough for the ambient pressure that I'm at right now.