Half Turned Valve

[Rick Murchison]

How does it jam?

Already against the stop, it gets bumped and jammed open. In a really bad jam, the little plate that slips over the square valve stem and the stem itself will strip so you can't close it. If you're lucky you can disassemble the handle and get to the stem with either an unstripped handle or a pair of pliers and break it loose, but sometimes it requires draining the tank through the regulator so you can get it (the reg) off, and the valve has to go to the shop for repair/rebuild. In the meantime you loose use of that tank (unless you have a spare tank valve in your save-a-dive kit )
Bottom line, I dive with the valve a quarter to a half turn off the full open stop.
Rick

 

[Walter]

Bottom line, I dive with the valve a quarter to a half turn off the full open stop.

There is no down side to that.

 

[klausbh]

Wow, in just three of years diving I've been through most of this!

Yeah, I have no idea why anyone teaches this ridiculuous practice. What on earth is the point of cranking the knob back a half turn!!

This is what I was told in 2003: the quarter turn is a thing of the past, don't do it.

I knew I wasn't in danger, but it would have been a different story with a single tank.

Within a year or so a friendly DM thought my "not quarter-turn-off" tank must be off (which is wasn't) and "corrected" that for me. Fortunately, he gave me a quarter-turn-on so at least I had some air to breathe while I figured it out.

Another time it happens is when you get to be an "experienced" diver and get interrupted sixteen times by other folks with minor problems before you can get in your own gear and hop in. This is when air can get left off, weights or cameras or spearguns can get left behind... I've heard tell that it's an awful feeling to be doing a back roll and to see your finless feet against the sky

I really hate the giant stride with the sunglasses.

By 2004 my incidents included:
valve closed - been there
no weights - done that
no fins - check
sunglasses but no mask - yup

If you're lucky you can disassemble the handle and get to the stem with either an unstripped handle or a pair of pliers and break it loose, but sometimes it requires draining the tank through the regulator so you can get it (the reg) off, and the valve has to go to the shop for repair/rebuild.

I ran into this last November. My valve handle didn't actually strip, but it was completely stuck. Fortunately, it happened after our last dive of the day and we were able to muscle it open with vise grips back on dry land.

I too was taught (in 1993) to back the valve off 1/2 a turn and I still do it religiously.

It appears that what they taught in 1993 wasn't quite so stupid after all. Ever since my "jammed valve" incident I have been a practicing the quarter turn.

Meanwhile:

You haven't really lived until you get one jammed on so that the valve stem fails before you can get it off the stop. It's an interesting problem from there on, involving draining the tank through your reg - for starters.
Rick

As of August 2006 I have really lived! My buddy stripped his valve stem and we had to drain the tank to get the first stage off.

Now if only I could accidentally fall asleep underwater one of these days...

Dive safely,

-Klaus

 

[Thalassamania]

As Mark Twain observed, "At 18 I thought my father a damn fool, at 21 I was amazed at how much the old man had learned in those three years."