Big scare Lesson learned

[yao]

In my opinion, there is a reason why my instrutor taught my to fully crank open the valve and then 1/2 turn back.

Case 1: Valve Fully Open
There is no harm to fully open your valve. But imagine this scenario, after you fully crank open your valve and for some reason you left it alone (maybe to help others). After a while, there is some probability (I'm not saying that it will happen) that you forgot whether you have actually fully open the valve or not (well, apart from breathing from ur reg while looking at the pressure gauge) because for both condition (fully open as well as fully close) you will experience that you can only turn the valve in ONE direction only (unless you can remember turning clockwise it is close and counter-clockwise is open - or the other way round...hmm...see what I mean?)

BUT

Case 2: Valve Fully Open then 1/2 turn back
There is also no harm as you'll still get your air supply, (if I take the same scenario as Case 1) you would immediately know whether the valve is open or close because
i) if it's close - you can only turn thevalve one direction
ii) if it's open - you can turn the valve at both direction

Of course, try to make it a habit to take breath a couple of time through the reg while monitoring the pressure gauge before every dive.

The conclusion? Case 2 is a first stage in helping you to identify whether your valve is open or close.

In your thread, you mentioned that you are tired after the long day and many dives. Even if you practice Case 1, you might ended up jumping down with your valve close.

 

[Atticus]

I initially learned the 1/4 turn technique in recreational diving, but when I started taking tech classes I was taught all the way open or all the way closed. About that time I started getting very sure of which way to turn the valve to get which result, so it worked out well.

The problem I have with leaving the valve somewhere between the stops is that there is no way to verify that it is 1/4 turn from open vs. 1/4 turn from closed. If a diver is comfortable with the position of a valve when he feels that it is against neither stop it seems to be that he is taking a big risk that there might be insufficient air flow at depth.

On the other hand, *so long as* you are in the habit of taking a couple of breaths while watching the SPG full open will work well for you.

It's an extra step, but IMHO it increases safety.

- Atticus