Why close the valve 1/4 or 1/2 turn???

[manumenzella]

Hi!!! I´m 15, and im new to scuba diving!!!
I finished the course some weeks ago. (That first breath underwater, was the best breath of my life )
I have a question: why do we need to close the valve 1/2 or 1/4 turn???
I always do it, because my Instructor told me, but i forgot to ask him why.
Sorry for my english!! Thanks!!!
Manuel

 

[hunter991]

Most dive instructors and dive masters always like to check the air on customers tanks before they jump in the water. It is an easy check to turn the valve a quarter turn open, and then back to the originial position. We do this without the customer noticing but it is a quick easy way to make sure that the tank is on before they jump into the water.

Brent

 

[agilis]

You don't have to. The 'open fully and then back off a half-turn' is an old technique without any real purpose. It also can be dangerous. Every diver is responsible for their own valve setting, and nobody else has any business touching or checking them.

 

[manumenzella]

Hi. Thanks for all the answers!
Youre right, its a nice and easy way of making sure the valve is fully open..
Also, as agilis said, you are responsible for your equipment. Thanks again
Manuel

 

[fairybasslet]

Yeah. Don't do it. It can mess up your pressure readings.

 

[Mafiaman]

You don't have to. The 'open fully and then back off a half-turn' is an old technique without any real purpose. It also can be dangerous. Every diver is responsible for their own valve setting, and nobody else has any business touching or checking them.

Right and Wrong, It is a very old school habit but the practice reaches out side the scuba industry also, In full open position as a tank drains and pressure reduces the valve can get stuck as things shrink ever so slightly.

 

[hunter991]

It is my responsibility to make sure my new uncertified divers have turned their air on before they giant stride into the water. It is just a safety check. Safety is my primary concern.

Brent

 

[beautybelow]

I am not sure with valves these days if there is any reason not to open them all the way. I understand when diving in an overhead enviornment that opening all the way creates a "lock" and makes it harder for an accidental roll off, so I can see the "it may be dangerous" part.
With that said, I will continue to check peoples air before they enter the water. If they want it all the way open, thats ok, but it is a habit to check them before they exit the boat. The one time I can remember I didn't was with another 15 year old diver. She was with her family, all good and experienced divers and I was the one that helped her putting on her tank for that dive. It was not a good feeling seeing her look at her gauge and swim towards her father...I knew immediatly what had happened. She was only down less than ten feet, but I felt responsible for the situation because I could have very easily checked her valve like I had thousands of times before and thousands of times after. Sometimes it is my business to do that.

 

[hunter991]

I understand what you mean about it being no ones business. On a dive boat I don't really want anyone fooling with my gear, or any any other dive for that matter. But as a rule I like to check before people get in, it is just an added safety measure.

Brent

 

[agilis]

I've seen more than one person jump off a boat with the tank valve closed, and none was uncertified. If anything, new divers I've seen tend to be more cautious. I've also seen a divemaster turn someones tank nearly off, open only a half turn. This individual probably had trouble with reverse image perception. I make cetain that my equipment is properly set up before I enter the water, and I do not permit anyone to touch anything. I've had one or two confrontations, but nevertheless, I insist. There is a lot of stupidity and incompetence out there.