Duane Johnson - Tech Instructor
The Purpose of Valve Drills
Valve drills are to technical diving as fin pivots are to recreational diving. If you have taken a PADI open water course in the past few years, one of the skills students do is the fin pivot. Basically, you lay flat on the bottom of the pool (or where ever) , keeping your fin tips on the bottom, and inhale. As you start to rise, you exhale. As you move back towards the bottom you inhale again. The point is to pivot on your fin tips as you move up and down. The whole point to this skill is that you use your lungs to fine tune your buoyancy to move slightly up or down in the water column. Other than that, you should never do a fin pivot in the real world. Here’s a video of the fin pivot.
The valve drill is held in the same regard as the fin pivot. That is, the valve drill as a whole, has no value except to demonstrate the ability to reach and manipulate one’s valves.
Valve Drill Truth
It has always bothered me why many technical diving instructors only teach the valve drill to their students and never go into any more detail about why they are manipulating their valves. The truth is that the valve drill is the building block of something more. There must be significant thought behind the valve drill. This thought process is called the nine failures. That is, there are nine possible failures that can happen when diving manifolded double tanks. The nine failures drill moves a diver away from the procedure of simply manipulating ones valves and moves them towards thinking about what is actually going on in order to fix the problem. In my technical diving class, I spend day #2 doing nothing but the nine failures. This is where I tell my students that this is their transition to becoming a thinking diver (assuming it is their first class with me).
Here is an example of a valve drill.
If you are contemplating taking any technical diving class, you should definitely discuss valve isolation with your potential instructor and get the details about what you will learn in regards to valve isolation. Don’t settle for just learning the mechanics of the drill. Learn the thought process behind why we manipulate our valves.
If you’re interested in learning about what the nine failures are, then take one of my technical diving classes. 
Dive Safe,
Duane
Precision Diving
About Duane Johnson
Good post Duane, IMO a lot of people don’t even fully understand what shutting down the left or right post actually does. I know that personally I didn’t truely understand the reason for valve drills until I was in a technical diving class where failures (sometimes multiple) where thrown at me with an air gun. I think some people have a very difficult time getting past the robot-like sequence of a valve drill when they are actually presented with a failure and that’s one of the hardest things to master with diving doubles let alone technical diving.
I found the combination of a fin pivot while doing a valve drill was very helpful. Keep up the good posts.
That doesn’t surprise me Dan.
Would it not be better to spit out your failing regulator, get on to your backup which is working properly before shutting down your primary. If for example you backup was not working or the hose would be stuck then you would be in a really bad situation.
Additionally the Navy practice the act of shutting down the valve and manifold if fitted at the same time…
nice video though
Hi James,
Prior to shutting down the long hose, we test purge the backup to verify that it is working prior to the switch. If you had a slow leak in the long hose and switched without purging it, then you will still see bubbles and won’t know if shutting down fixed it or not.
Duane
Hi Duane
While that works in a controlled environment like training what about in the future.
The first time that happens people get anxious and their breathing increases. I feel it’s best to resort to a secure reliable source of air before putting the effort into shutting down the problem. The act of the shut down can cause some to have accelerated breathing.
I was taught this as a diver in the military and it’s something i teach from the beginning to tekkies.
This method also relates to decompression. If a student is breathing pure oxygen and has a failure they are taught to “bail out” on to back gas because they might loose buoyancy and drop below the pp02 in the reaction… in this instance beyond 1.6… This also sets them up later in life for rebreather diving where you get off the stove before you turn off the flames.
Nice to chat about it though