Half a turn back

[RonFrank]

I have no clue what "Jammed Open" means, and I'm betting CatFishBob does not either!

Valves are valves... they are fully open, partially open, or closed. There is no such thing as full off, it is either closed, or not. I recommend the fully Open position when diving! I open mine all the way, and leave it that way. I've never had an issue, and have never met a diver that did.

The amount of air that is deleivered has less to do with the valve (assuming it is fully open) and more to do with the first stage. If you doubt this open a tank withOUT a first stage attached, then see how long it takes to empty the tank. Now repeat the process with a first stage attached! Questions!?!

 

[GrumpyOldGuy]

Turning the valve 1/2 turn back from full open does have one advantage. You can take a relatively simple screw up (like someone having a brain fart and mixing up direction) and instead of detecting the issue on the surface and correcting it before descending, you can delay detection of the problem until you have descended. This is much more exciting, you (or a dive buddy in the event you don't make it) can write it up in the accidents and incidents forum.....

 

[Captain12Pk]

I know this has been covered here before, but here goes.
the reason I do not believe in the "quarter turn back" theory is that in the event of an in water failure, neither team member has to worry about that " oh sh**, am I turning it the right way" moment. It'll only go one way, closed.
And FWIW, only two people are allowed to touch my gear. Me and my regular buddy. No DM's no boat Captains, nobody. But where we dive, the DM's and boat crews always ask prior to touching. So no problem there really.

 

[Teamcasa]

Old valves (circa 50's-60s') could be jammed in the open position. Newer valves can not unless magilla gorilla cranks it open. Open the valve all the way, dive and have fun.

 

[ligersandtions]

half a turn not half way back... this will never affect air flow, but keeps you in the safe side in case it gets stuck if fully opened.

Not half the way back, half a turn. It takes several full turns to go from full off to full on.

I was told to do it, so that the person checking the tank could easily tell it's state. All the way on, and they might presume all the way off.

Ahhh, thanks! I totally mis-read that.

 

[CamG]

Greetings sphenisc and welcome to Scuba Board! This is a good question that was just brought up on the Basic forum last evening. The practice of 1/4 turn valve back was to ensure valve not to get stuck open and to supposedly prevent internal damage to your valve. With valves that are in use today most if not all function fine turned all the way on and left that way.
Now the draw back to the all on back 1/4 turn is.....it is possible for a DM or buddy to get confused and turn your air off and on only a 1/4 of turn. This means that at the surface you will seemingly have air until you descend and the ambient pressure builds up enough to prevent proper flow to your first stage. This can lead to a OOA at depth situation. Not really what we as divers strive for. This does happen and I have witnessed it personally, buddies are really appreciated at times like those. No big deal just a simple check solved the problem. But the what if......made the post dive de-brief a little more serious. The boat hands were told to hands of our regs and tanks. We did our own tank swaps and air all the way on or all the way off!
The reasoning behind the all on is if someone accidently shuts it off you should catch it before entering the water. It does happen and it is easy to deal with at the surface.
Out Of Air situations at depth should be avoided by all means! I am sure that many will disagree with me but this is the practice I keep and the instructor I assist teaches. I feel and my opinion is that it is just safer.
CamG Keep diving....keep training....keep learning!

 

[LeadTurn_SD]

Turning the valve 1/2 turn back from full open does have one advantage. You can take a relatively simple screw up (like someone having a brain fart and mixing up direction) and instead of detecting the issue on the surface and correcting it before descending, you can delay detection of the problem until you have descended. This is much more exciting, you (or a dive buddy in the event you don't make it) can write it up in the accidents and incidents forum.....

Bingo.

This is exactly the reason the valve should be OPEN or CLOSED. Nothing in between.

I started diving when the "open all the way, then close 1/4 turn" was taught (and, as an unrelated side note, was also taught this procedure as a Mate on oil tankers, where an intake or discharge valve stuck open could ruin your whole day ).

There have been too many instances of divers entering the water with the valve only opened 1/4 turn because they or an overly-helpful boat crew forgot "righty-tighty, lefty-loosey".... they can still get air and all seems fine on the surface, then they get down to maybe 40-50 feet, and suddenly believe they are OOA. Not good.

Open them thar valves all the way, "valve stickage" be damned say I!

Best wishes.

 

[liuk3]

Regardless of how you do it, I'd just make sure that I can reach my valves and open/close them. This seems to solve potential problems and was taught to me in my OW class. FWIW, I started out doing the partial turn back on the valve, then switched to fully opening my valves, and have now come back to doing the partial turn back for reasons of not getting the valve stuck. The valve did stick on me once while doing valve drills, so it kinda made me a little paranoid.

 

[lemon]

Leave your valve FULLY OPEN.

I've personally witnessed two different divers on two different occasions lose their full air flow at depth because the valve was just a bit too closed. Once in Palau and once in Belize. The first time was only mildly alarming, the second time a diver panicked and did a CESA from about 50 feet. Fortunately nobody was hurt on either dive but the second guy did sell all of his gear and quit diving for good after his episode.

Personally, I think this is an old tradition that should be ended. (that's my 2 pesos worth!)

 

[stedel]

I am a PSI certified tank inspector. According to our instructor (the founder of PSI) the routine of turning the valve back a quarter of a turn (or so) stems from the old valves that did occasionally get stuck in the wide open position. It is true that this is not a problem these days with modern valves. It is also not true that a valve is either open or closed as it takes several turns for a valve to be fully open. The best practice is to open or close the valve fully but you don't need to crank hard on it either way, simply fully opened or fully closed.