OOA after only a few minutes with a full tank at 17m

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FWIW, I still turn my knob back a quarter turn and teach it that way to students. A valve all the off or all the on feel exactly the same. A valve a quarter turn off, feels "loose" and easily differentiated between all the way off. Yeah, I check all my students' tanks before we splash.
If your valves still look like this:
oldvalve.jpg

then yes, you have to turn it a bit back. These old valves were a nuisance, the construction may cause the valve to jam when fully opened, due to expansion of different metal types inside the valve, caused by the decompressing air which draws heat from the surroundings. Alec Pierce explains this on YouTube.

These valves were used in the previous century. Nowadays, valves have the knob on the side and are constructed differently. Opening the valve all the way with your fingertips is the correct way.

Reason for using your fingertips and not your whole hand:
IMG_7969.JPG

Inside the valve, on the stem, is an o-ring that does all the work for you, keeping the air inside the tank and preventing any leaks. If you force the valve fully open, that o-ring is squeezed between the stem and the teflon ring inside the nut.
On the left you see what this o-ring should look like. On the right you see o-rings that are worn-out by using force to open tanks.

Fingertips
All the way open
Even if instructor Pete says "quarter turn back" (and I hope your students read this :wink:): all the way open
 
In theory we should all be opening the valves holding the handle only fingertip tight anyway, this should prevent it being jammed into the stop and knackering the internals or binding.

I personally crack the valves back so they’re fractionally off the stop, literally a degree or two of rotation.
 
Well, I'm with @The Chairman . Sorry @JohnnyC ! Rec diving isn't caving, and I'm not worried about rolling a valve shut on the overhead.
The problem with "lefty loosey, righty tighty" is that not everyone gets it. As pointed out above in this very thread, folks have had friendly boat crew roll their valve off!!! And someone who is uncertain about which way to turn may take my fully on valve and, thinking it's off because it's tight, really honk the handle in the open direction. I don't need boat crew stripping my plastic handle, even if it leaves the tank on for the dive. And damage to the sealing oring on the valve spindle neck from opening it too hard, was described above.
With the tank handle cranked back a hair (not even a quarter turn), I can feel the crew's check on the rail before I jump. If it's a one second check, they probably felt my loose handle and opened it further, against the stop. If they take longer, then I know they're turning it in the wrong direction, and I step back off the rail and check it myself.
As The Chairman noted,
A valve all the way off or all the way on feels exactly the same.
I get a little irritated with folks that are adamant that their way is the only right way. I get what you others are saying. You're not wrong. But for the reasons I just stated, I teach my students to crack it back, while also telling them that they're going to eventually run into a know-it-all who may yell at them for doing it that way, and that they need to decide for themselves what they want to do.
 
OP, when you did your three derp breaths at the surface, did you watch your pressure gauge? The needle should wobble if the valve is not fully open.

Old wives tale. The check might work, depending on the valve, but will never tell you if he valve is open, only that it is not shut.

If the thread goes on long enough I might come back with my full rant, however it is another example of training by catchphrase instead of teaching the information a new diver should know.


Bob
 
Don't turn your valve back. Seriously, don't. Whatever reason you were told is invalid with modern valve design. It's not an acetylene bottle that you're gonna wanna slam shut while it's on fire..... Open it all the way then don't touch it.

Open your valve all the way. Check your SPG when you pre-breathe. Check your SPG during descent. Open your valve fully then don't touch it. Should I say it again? Any other techniques? Yep, get a different instructor. There's no reason any instructor in this day an age should be telling open water students to do anything with their valve other than open it all the way and leave it.

As an aside, the cases that call for otherwise don't belong in the basic forum.

And in case anyone missed it the first time, open your valve all the way and then leave it, do not turn it back a quarter, a half, a thirty second, any turn whatsoever. There's no reason we should be seeing posts with this type of failure on this forum. The fact that it is a fairly regular occurrence is distressing.
100% correct Johnny.
Create a routine and don’t deviate from it. Build your gear. Turn the valve completely open. Breath your regs. Watch your pressure gauge. Leave the valve open. Do this - build your gear. Pressurize the system. Shut the valve. Take normal breaths. How many breaths did you get before being OOA? Now you know how many breaths it takes to empty the system - add one more breath and you know how many sample breaths to take to know the valve is open. If the answer was 3 + 1 = 4. Now when you are ready to donn your gear - check the valve is open 100% and take 4 breaths for the system. It confirms to you that the valve is open. Also - take the attitude that NO ONE assembles my gear except me. No one changes tanks except me. No one does anything to my gear except me. Period.
 
I don't back off a measurable amount, but I prefer to turn the valve back a small notch from "stuck on fully open". It's probably my OCD showing. Again.
Yeah, it's probably closer to an 1/8 of a turn... just to keep it loose to the feel.

Notice that none of us are worried about it jamming open. I did see a beast of a fellow wring the knob off of a valve trying to open an already opened valve. His first comment after the cussing died was that the valve wasn't loose. It was hard to dive I was chuckling so hard on so many fronts. First they were going to drain the tank to get the tank off. Someone suggested that he should just dive it as it was and use the air first. After the dive there was all sorts of discussion about how to accomplish it. Someone said "Drain the tank", which was the best option. Luckily, I caught them about to undo the gland nut holding the stem on the bad tank. That's safe only when the tank is closed.
 
Looking at your SPG while doing this would have discovered the problem. Normal: very little movement. Slightly open: needle sways back and forth.
I have found to move the needle requires the valve to be a crack open. Given that I dive sidemount, not really an issue as no one can turn it off for me but me.
 
This happens more often that most people would like to admit. Be it from “help” or “forgot” it amounts to the same. A visual check is a good thing.

Products
Sometimes. I put those on my LP120s after a DM turned my "lefty" tank off while walking back to the transom. They still managed to turn it off with the vindicator knob showing green, green, green. Consequently, I modified my routine to include another couple breaths on the transom and not just at my seat. I also developed a strategy to keep the DM always in front of me and not able to check my tank. They assumed I was going to do a giant stride off the back, where I do my "back sit" instead.

Routines are good. Just don't let anyone interrupt you or be ready to start from the beginning.
 
Sometimes. I put those on my LP120s after a DM turned my "lefty" tank off while walking back to the transom. They still managed to turn it off with the vindicator knob showing green, green, green. Consequently, I modified my routine to include another couple breaths on the transom and not just at my seat. I also developed a strategy to keep the DM always in front of me and not able to check my tank. They assumed I was going to do a giant stride off the back, where I do my "back sit" instead.

Routines are good. Just don't let anyone interrupt you or be ready to start from the beginning.
Too bad we love red/green so much as a binary choice of indicator. Up to 8% of men from Northern European descent are red/green colorblind. May have included your DM.
 
May have included your DM.
He was simply too broke to pay attention. He got confused over the lefty valve and turned it off. Now I don't want them touching it.
 

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