Valves "full open" or not?

[Flightlead]

comments in the "when do you do a valve drill" thread prompted this question.

Do you turn your valve and isolator knobs all the way in the open direction when diving?

I have received instruction that it is better to only turn the knobs 1.5 turns to the open direction. this is based on

1) the design of the valve is such that once the knob has been rotated 1-1.5 times the valve will fully flow (IOW after 1.5 turns the valve is fully open). turning the valve any more will not increase the flow capability of the restriction,

2) closing a valve in an emergency is MUCH quicker when you only have to turn it 1.5 turns rather than 6 or seven. this might save you several seconds of gas loss.


comments?

 

[Jimmer]

Either fully open or fully closed, that way there is no confusion in a stressful situation. Plus the 1.5 might flow fine at the surface, but how about 120 feet, if you didn't get quite 1 turn and only got .75?

 

[potablewater]

I agree with full on or full off with all gas valves. But, there is a lot on this subject to be found on SB and other sites that break it down to a science...ala "...full on and then back off 1/2 turn..." kinda things. It seems like good reasoning, but when in doubt cut it all the way on!

All the best,
Geoff

 

[Rainer]

Fully open or fully closed. You do NOT want to get confused (and it can happen to anyone if stress is high enough).

 

[deepstops]

Fully open or fully closed. You do NOT want to get confused (and it can happen to anyone if stress is high enough).

Ditto.

 

[texdiveguy]

ALWAYS when diving...Full Open!

 

[TSandM]

Full open, although I back them off just a tiny bit to make sure they aren't jammed open. I've tried to close a valve I couldn't turn before, so I'm careful to make sure they're never set anywhere where they are difficult to move.

 

[Rainer]

Full open, although I back them off just a tiny bit to make sure they aren't jammed open. I've tried to close a valve I couldn't turn before, so I'm careful to make sure they're never set anywhere where they are difficult to move.

Ok, so I back them off slightly as well. Not just so they aren't jammed open, but in case I *did* turn them the wrong direction, I wouldn't be jamming them. A jammed valve is a pain to open (have done it once and decided to call in a buddy to loosen it).

 

[piikki]

Fully open and fully closed but I also do that teeny nudge in the end to prevent jams.

The funny thing to me is when some people say that they vary things in different environments. This only goes for doubles but some people say they dive isolator open in OW but half closed in overhead. I see the reasoning, yet it makes no sense to me to vary it between dives.

Also same people say their valve drills/valve protocol is different in OW vs OH. In OW they'd start with right post (if not immediately clear where the prob is) but in OH they'd go for isolator first. I have not been trained for overhead, so I do not know what is being taught but to me it sounds iffy to have two different protocols. But I digress...

 

[Arizona]

I remember reading somewhere that fully open was correct. Almost everyone I dive with including instructors like to go full and then do the half turn back. Is this still the standard for PADI? I am going through the IDC in a few months, so I am sure it will be covered there.