Adobo, we'll agree to disagree, if you follow the steps in the GUE valve drill, there is pretty much no way to fubar it since you are verifying everything after you do it. Did I shut it off? Well I purge or take a breath and the hose goes limp, so check. Did I turn it back on? Well I see or feel the hose pressurize, and I can breathe off of it, and I'm always breathing off of the other hose than the one I'm manipulating. Just not sure how you can screw a valve drill up following those procedures. I looked up the actual one in the GUE manual and it's like 13 steps, that are pretty idiot proof. Only time you can shut both off is if you just aren't doing it in the right order and verifying everything works before switching.
Since you are using GUE as the example... do we even know why the valve drill is taught in fundies?
I was on a dive just yesterday where my GUE trained buddy did a valve drill. Either he did not check his backup reg for gas or I did not see it. In either case, he started turning off his right post so I stopped him just to be sure that he had a working reg to switch to.
Per GUE, it takes two divers to do a valve drill. If the OP has a trained buddy, that buddy should show him how to do the valve drill. In this way, the trained buddy can see if the the OP is doing the valve drill properly or if the OP is about to wind up with two posts that are turned off.
If the OP doesn't have a trained buddy, what is the point in learning the valve drill in the internet? Is the OP going to teach one of his friends to do the valve drill that he learned in the internet?
I guess I just don't see what the point is, especially when it is perfectly reasonable to dive doubles in recreational dives without introducing valve drills.
I suppose if I was pressed for "tips" for diving doubles prior to taking intro to tech or fundies or some sort of doubles primer, I would say, keep it simple.
---------- Post added November 10th, 2014 at 01:50 PM ----------
While I am not a technical diver, or obviously even a doubles diver at this point, I disagree. In my dictionary, in a technical dive there is no direct access to the surface. In recreational diving, there is. I don't believe that means you must take advantage of it. If there is a failure, and I am trained to handle it (which I plan to be), I am not going to be grabbing my buddies long hose without attempting to handle the situation.
Well, I can appreciate that different people have different opinions but I find it hard to get around the fact that if you have a post or manifold failure, it will take not one but two trained divers to deal with it under water. This has nothing to do with agencies and everything to do with the fact your eyes are not on the back of your head. So by virtue of you soliciting advice in scubaboard, I am inclined to think that there aren't many dive buddies around you that could help you debug a failure even if you had the training.
Regardless, in a single tank, if I have gas leaking from my first stage or the tank valve, the first course of action is not to get gas from my buddy anyway. I would get my buddy's attention, show him that I hear bubbles and then I would thumb the dive. On the ascent, I would monitor my SPG to see how fast I am losing gas. If I can, I will complete my ascent on my own reg.
Which is exactly what I would do if I were doing a recreational dive with doubles.
I don't want to be attached to my buddy sharing gas unless it is necessary.
Thanks for the advice
You're welcome.