Why do you not turn a tank full on ?

[Genesis]

You'd be shocked at how many Ow divers can't REACH their valves.

It was one of the things that a couple of friends of mine had drilled into their heads, and they understand the value.

Otherwise, the first time you really NEED to reach it may be your last. And some idiot DM on a boat may well be the reason you cack yourself some day if you can't get back there with a singles rig and turn it on - you jump in with no air in the BC, sink, and have no gas supply.

You're hosed.

 

[MikeFerrara]

sasdasdaf once bubbled...
Hence the importance of being able to manipulate your valves underwater quickly and instinctively.

Of course but it isn't required in any OW class that I know of. They don't even have to hover (not really) let alone manipulate valves midwater.

I mean could you see the average recreational diver (at any cert level) have to manipulate a valve on a wall somewhere? Next stop 1000 ft (or the surface).

 

[sasdasdaf]

Unfortunately you guys are right. As important as some of these "fundamental" skills are, almost nobody teaches them and few divers can do them.

I've heard enough strories of so and so who fell off the boat while getting into his doubles and sinking, never to be seen again. That was enough to motivate me.

 

[MikeC]

Karl_in_Calif once bubbled...
Today we teach students to turn their valves open slowly, then all the way.

No more 1/4 or 1/2 turn back.

Modern valves do not need to be turned back at all.

Please define "modern". When did the modern valve hit the market?

Also, what about tanks you get south of the border that may or may not see any service during their life?

 

[Axeman]

I was told to turn back 1/4 turn so that if the valve handle hit something (cave/wreck) it would not break.....

I haven't had any problems with it yet....

I am religious about checking to make sure my air is on BEFORE I leave the boat.

 

[PhilD]

fritzer once bubbled...
Supposedly, and it seems feasible, the pressure at depth can actually tighten the valve to the point that it's impossible to turn once you're back on the surface.

I was diving on a boat all weekend with a tank that belonged to the boat and I noticed a similar thing. With the valve fully opened, it would be very stiff to turn off, not impossible, but substantially harder than usual. If I backed it off just a fraction, there was no problem. Maybe it was an old volve, or needed surfacing, but I could see how a valve could get locked open this way.

 

[lragsac]

BILLB once bubbled...
What an interesting set of explanations. I personally do not like gimmicks that are used to replace knowledge and mastery of skills.

My students are instructed to turn the tank valve completely on. Which way is completely ON is a skill that every OW student MUST master. As a diver, you must first be able to do all the required skills without assistance from others. Depending on others to check your tank valve is a buddy function but without the gimmick of a 1/4 turn, etc.

As stated in this thread, there are no longer any mechanical reason to continue the practice of backing off 1/4 turn. Cave Divers always turn the tank completely on.

Seems to me you should train to the point of sheer muscle memory. Should be as automatic as knowing where the accelerator and brake is on your car. Anyway, glad to see an instructor training students in this way.

 

[Squasher]

Genesis once bubbled...
You'd be shocked at how many Ow divers can't REACH their valves.

It was one of the things that a couple of friends of mine had drilled into their heads, and they understand the value.

Otherwise, the first time you really NEED to reach it may be your last. And some idiot DM on a boat may well be the reason you cack yourself some day if you can't get back there with a singles rig and turn it on - you jump in with no air in the BC, sink, and have no gas supply.

You're hosed.

Arent you suppose to know your equipment?? Test your gear before you hit the water? e.i. turn your tank valve on, close it, breath through the reg until nothing comes out. count how many breaths you took. than before every dive breath through your reg more than the number you counted.

 

[VTernovski]

I was told that the reason for turning the knob 1/4 back is that ifyou hit the valve on to something it won't get stuck open that you won;t be able to close it. This is a especially true for single-cylinder diving.

Anyway, I don't see any really good reason not to do this.. anyone can add any comments? there is no performace issue with turning the vale back about 1/4 of the revolution.

 

[Genesis]

hard enough to cause the valve to get stuck in that fashion if its all the way open you will also do it if its backed off 1/4 turn.

Is there a performance problem with the latter? Probably not. But if you get underwater and have a problem with airflow, do you want to guess which way to turn the valve, or KNOW which way to turn it (because it only rotates one way)?

If its either OFF or ON, then there is no maybe about whether its a valve malfunction underwater or not. If its against the stop, then either it should be delivering NO gas or ALL the gas.

Not having to play guessing games underwater is a plus.