Quarter turns

Do you back off a quarter turn?

  • Yes

    Votes: 57 46.0%
  • No

    Votes: 67 54.0%

  • Total voters
    124

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Does one measure a quarter turn? I turn it back one "hand" turn. Because I read you should do that. Doesn't sound like a DM response, but I have had no problems ever doing this, and I can easily tell where "on" and "off" is when I'm done for the day. Perhaps I'm 10% dislexic. "Righty-tighty, Lefty loosey"--what does that mean to a putz like me when you're looking DOWN at a valve?
 
I back it off a bit. Originally because that’s what everyone else was doing, and later because of an explanation given me by an experienced military diver. If diving in roiled waters, sand or other grit can find its way in and jam it. It’s easier to work out a jam if you have two possible ways to turn the valve. Never experienced it myself, and not even certain it’s a real concern, but it’s easy to maintain old habits, and does no harm.
 
1/4 turn back, Yup. Original training lives on.

Tapatalk -- If you are offended by anything in this post, then my efforts have been rewarded. :D
 
Quarter turn? Maybe not quite that much, but I do turn it slightly back so its not "tight open"..
 
I haven't read the other responses, but I don't turn it back a quarter turn. Rather, I turn it back just a hair--less than even a quarter turn. My understanding of the rationale behind that bit of teaching was that you don't want to jam the valve in the open position such that you might have to exert a large force to un-stick it when it comes time to close it. So I open it all the way until it feels like it's completely open, then just sort of make sure it isn't jammed open. Sometimes that means backing it off just a hair, and sometimes it means just leaving it alone, depending on how forceful my last turn of the knob ended up being.

Wow--that's a lot of words to convey a simple concept. No wonder the agencies teach simply backing it off a quarter turn!
 
I learned it well before SCUBA, my dad was a Machinist Mate in WWII and I assume he picked it up there, may be earlier. The theory is that some valves have a tendency to jam when backseated (some are at 100%) so take all valves off the back seat and avoid the problem. Quarter turn is something easy to remember. If you know the valve can be backseated according the valve specs and useage, no problem. If you look at valve design, you will find valves are at 100% flow before they are completely open, with the exception of ball and gate valves, neither of which are used for metering fluids.

I started when I was four or five so I doubt I'll be changing the practice soon.


Bob
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I my be old, but I'm not dead yet.
 
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I don't understand the wear. All of the threads are engaged no matter the position, and the seat is either touching the orifice (valve closed) or not (valve open). How open you have it will affect flow rates, but I don't see how it changes wear on the valve.

How many of you open and lubricate your valve yearly?

If it is CRANKED open it is putting tremendous crushing pressure on the little stem O-Ring. YES??
 
Fully opened. Thumb and index finger strength.

However, when filling tanks, I back both valves off. Reason being that I'm working a lot faster when changing tanks and it's too easy to crank them fully on.
 
I voted yes to backing off a quarter turn since it was the closest answer, but like many, I just back off slightly from fully on, perhaps it's like 1/10 to 1/8 of a turn.

I was keeping it on fully for a couple of years, but it caused a lot of confusion in other people and I had my valve turned off twice by DM's, although I caught it before I splashed. I eventually went back to the slight backing off.

I had a new issue last week in Grenada. I went to turn my tank on before putting my rig on and it wouldn't loosen, so I asked the DM, "Did you turn it on?" He said "No", so I tried to turn it to the right and it wouldn't budge that way either. I tried again to loosen it, and I couldn't budge it. I tried as hard as I could, and it finally opened. If I wasn't in the habit of making sure, I could easily have believed it was already open, though it would have been caught on my next test of breathing while watching the pressure.
 
I do it because that is what I was taught. I don't think there is any mechanical reason for doing it but the last thing I do before a student gets in the water is check his valve if it does not easily move is it firmly closed or firmly open?

I am firmly in the don't back it off camp, in part because I don't firmly open it - there is no need, and if you don't do it firmly, there is no reason for it to jam.
 
https://www.shearwater.com/products/perdix-ai/

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