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

[Diver Dennis]

I wish everyone who comes to do a recreational "vacation dive week" did the same thing as you....trust me there. But the fact of the matter is that in my experience, over half of the divers that I take diving are not like you. A lot of them do ask, most don't. Most of them had to be reminded how to put their gear (even perssonal and not rental) together. I think unless you have really dealt with the "general diving public", you may not have an idea of how many people go diving everyday with little experience or all that they have learned, forgotten. They certainly don't spend time on the internet learning about scuba diving, so most aren't reading this post. Like it or not, I am their buddy, the one that gets them in the water and back out safely. It's what I choose to do for a living, so I don't complain or talk down to them because they can't set up their gear or don't understand why they can't dive to 100 ft for 45 minutes even if they have the air left to do that. I just smile and say, yes, your air is on if they ask. If they don't ask, I have checked already and know for myself. It does make it easier if it is turned back a little to do a quick check, although I don't think that is why it is taught.

This is exact description of what happens "out there". I do all my diving in resort type atmospheres too. Things are not the same as local diving with the same people all the time. We dive with a lot of folks who do, as with most certified divers, less than 15 dives a year. I think that is one of the reasons there is mis-communication sometimes here on the board. Resort diving is very much different than diving at home.

A lot of us have different views on diving because of the venue and for us, not diving with regular buddies at dive sites you have been diving for years.

Excellent post BB.

Yes, I do leave the valve 1/2 turn closed. No big deal.

 

[agilis]

I think I understand your situation, BB. I've been on many recreational dive boats in the tropics over the past 30 years, and I wholeheartedly agree that many if not most divers on these boats have very limited skills. Some are just plain dangerous. This tends to not be true in more demanding dive locations, like here in the North East.

A good many vacationing tourists in tropical resort settings seem to think the world is an enormous theme park, a Disney construct in which their well-being is somehow assured. I don't blame people in the industry for taking whatever precautions they can. I generally try to stay as far away from other divers on these trips as I can arrange. I have not seen as much as you professionals, but I've seen enough to make me very wary. I think dive resort operators develop an intuitive feel for who will be a problem and who will not, and I am usually able to work things out and follow my own protocols. When that's not possible, I don't go.

 

[nice-diver]

Older valves also had a tendancy to seize on if fully opened and left there. One of my tanks with an old (10yr or so) valve did stick on in this way during a freeflow.

Probably not an issue these days so comes down to personal preference.

10 yrs old...my newest tank is 19 yrs old.

I open and slightly turn back so I know that if it turns when it is "dry" it will turn when I get back up, its just what I do

if you stand behind my doubles one valve rolls forward the other rolls back to open

 

[Puffer Fish]

Over the years, I've heard a couple of reasons:

1. The getting stuck issue.

2. The potential for valve damage if the completely open valve knob is hit and pushes against the stop.

I don't know that either are real issues, and has become a sort of ritual...

 

[oly5050user]

OK, other than it is an old school thing, here is my 2 cents.

some times people do get confused (even though the famous Righty tighty lefty loosey exists in all our minds) but if your valve is either open all the way or closed all the way you might get confused! so a good way to clear that confusion is to have it a 1/4 closed, that way when you check your valve rotate it right rotate it left and if it stops rotating after a 1/4 rotation then its open, (that's why i do it).

but if you think your mistake free, then don't do it!

thats the reason why..been teaching it for that reason since the 70's..has nothing to do with the mechanical workings of the valve..people get confused ..

 

[Arete]

I used to work in professional rope access. We used to do up everything fully, then back half a turn, then open fully and back half a turn.
For climbing equipment it becomes a safety issue if something gets jammed open or closed and you need to access that piece of equipment in a hurry for some reason.
I was told the same technique applied for scuba tank valves so they didn't jam open, and after having done it dozens of times a day every day for a couple of years it came as second nature and made sense.
(No I don't close it then open it half a turn when I store it )

 

[Cudabait]

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.

Correct Answer.

Regards,

 

[fasorud]

I believe it has to do with the inner workings of the valve itself. We do the same thing with the valve on a oil well and its not so someone can come by later to check if its open. Everyone watches him open it and make sure he turns it back 1/4 turn.

This is exactly why this is done. When you open the valve all the way, you are squashing an internal oring. By backing it off 1/4 you relieve the pressure you are applying on that o-ring, making it last longer and less likely to fail on the dive.

It is the same reason they tell you never to over-tighten an oil filter or oil-pan screw, because you will damage the oring and have leaks.

 

[agilis]

If valves were harmed in some way by being fully opened, logic suggests that they would be designed to not open that fully. I'm no engineer, but I don't think I've seen any valve manufacturers cautioning about over opening a valve. Scuba valves are single purpose devices, and have a full open position as part of an intentional design. If scuba valves functioned best opened only, say, 90%, the design of a highly engineered life support HP air valve would be flawed if the valve could be opened beyond that optimal point.

I think the quarter turn back from full is more an operational protocol designed to inculcate certain habits, like not jamming a valve open by applying more than light finger pressure, making repetitive checks and rechecks systematic in certain large applications, the need for consistancy to be drilled into operators, and the different ways some valves function, especially water valves. I think ritualistic behavior may also be involved.

 

[lamont]

If I manipulate someone else's valve, I always turn it to full-on. This is so that in the case where I've had a brainfart and turned it full-off that they find out about it in a breath or two.

I had someone on a boat do the off-but-1/4-turn-on trick on me because they got it backwards and it resulted in me throwing an OOA at 60 fsw.

For my own valves I do the 1/4 turn back. It means that when I do a flowcheck I can feel it hit the stop. There's also the issue that in an overhead environment (or tagging something on your manifold scooter) if its at the stop it may seize or the handle might break -- dunno how much that is voodoo, but it seems sensible...