Another scuba question, this time about the cylinder valve.?

Question

Those of you who read scuba questions regularly, know that I'm a newbie diver, and I'm hooked. I'm trying to learn all I can topside, so I read quite a bit.

I was never taught that the cylinder valve should be turned back 1/4 turn or a short way... in fact, in my confined water dives and the others that I've done since certification, I've never done that; I've just opened the valve.

My b/f says you should turn the valve back a bit, I've read it should be turned back in a tips booklet published by Scuba Diving magazine, yet on the Scuba Diving website, it says that the valve, once opened, should be turned back a bit or NOT AT ALL.

What is the correct procedure?

Thanks!

Answer 1

A valve is a piece of equipment that controls air flow. While 1/4 turn closed from the fully open position will not restrict air flow very much, you want all the air you can get so open it all the way. The worry that the valve may stick open is a fallacy. If there is a worry about the valve sticking open, you had better get a new valve immediately. The mechanics in the operation of a tank valve are quite simple and unless there is a serious mechanical failure or serious neglect, it will not "stick" open as many have been falsely taught. But to summarize, it really doesn't matter full or 1/4.

Answer 2

It depends on situation and what you consider are the risks on a dive.

The reason for the 1/4 turn back is to prevent that valve from sticking open.

The reason for having the valve fully open is to have positive and immediate feedback if a valve is open and what direction to close the valve while on a dive.

For recreational dives in less than 100' in open water, you may feel like preventing a sticking valve is more important than knowing which direction to turn your valve.

However, for diving in an overhead environment (decompression, wreck, and caves) it's prefered to have the valve completely open so you know your valves are on, and you only have one direction to shut them off if the need arises.

Answer 3

Open it fully (not hard) and back off 1/4 to 1/2 half turn. No more or you may cause turbulence in the 1 st stage (heat it doesn't need) and potentially causing condensation in there. Not a good thing for the reg and definitely bad news if you're diving a normal reg and even an environmental, in freezing conditions. It can also cause a possible a supply issue at depth, when you need it most. Leaving it fully open, could cause the valve to stick, making detaching the 1 st stage a vexing experience to say the least.

It is part of the course, you may have just missed it. I've seen Instructors whip through that part mumbling.

Edit: I disagree with Don on the fully open part regarding overheads etc. So NOT true nor taught in any wreck course or technical diving course. You ARE taught to know your manifold without the need to think. If indeed you do start to turn it the wrong way, the little it has been shut is an immediate indicator. Also, when it's backed off just that little bit from open full, it has NO impact on supply or smoothness of flow to the 1st stage.

Edit: Yup, ask your buddies, they'll agree. As for the fella that answered last...well I guess he's never seen one occur nor read even the OW manual from PADI ( I dug it out, it's in there.). It DOES happen. Just like that outdoor tap that you opened too far and need a wrench to close.

Due to the amount of dive related questions that are popping up, this evening during a social at the local pub, I asked a pal of mine that owns a 5 star Padi to join under his shop's name. A number of years ago, this man saved my life on a wreck dive, and he's about to become a PADI Director. That's about as high as you get in that particular org as well as standing in my book. I'm not an instructor ( I got bugged again to do the course tonight for free), hence my reluctance to put the word of "god" into some of my answers here. Mine is strictly advice and experience.

He can. Hopefully he'll join.

If you're curious, his shop's web site is www.coltcreekdiving.com

heck, I think there may be a pic or two of me in there too.

Answer 4

I agree that the valve should be backed off a 1/4 turn at all times.  Like stated above to keep it from sticking.  Really if you are a recreational diver once your in the water there is no need to be playing with it right? Unless you forgot to do a pre dive check and forgot to turn it on all together??  oops.  If its not open enough you can watch the pressure on your console dropping as you take a breath.  Have fun!!