Do you turn the air off or leave it on after setting up on a tank?

[johndiver999]

Agreed. I have never found myself in the water with a full tank that I can't breathe from, and don't intend to. Although, like tbone says, for divers who practice manipulating the valves underwater, the stakes aren't all that high, since it can still be easily fixed in-water.

You should carefully consider this assumption of "the stakes are not high". I would argue that the stakes are very high, in fact the diver may well DIE if they don't accomplish the task. You might feel the problem is easily fixed, but that does not mean that the stakes are "not high".

This is not a trivial point or semantics. What you may not realize is that some divers enter the water in a negative condition and may immediately begin a head first decent and some (advanced) divers might even consciously avoid inhaling deeply in order to stay as negative as possible for the first 10 or 25 feet of descent. So you could easily have a diver who is swimming down hard, sinking fast, takes a breath from the regulator, slowly exhales and now is even heavier and is 35 feet down and then pops his inflator a little and then tries to clear his ears and simultaneously tries to inhale and there is NOTHING. Nothing to breathe and there is no immediate solution to the negative buoyancy situation.

So now the divers is sinking, is heavy, his ears are hurting enough to be a huge distraction and will soon be subject to barotrauma and if he delays for 3-4 seconds more before figuring the problem out - his ear drum will rupture and now has to make the decision to
(a) drop weight,
(b) swim up like hell,
(c) locate his buddy and communicate the problem and secure a second stage
(d) locate and then switch to his octopus - obviously a bad decision in this scenario, but one that a diver might try in an emergency
(e) TRY to reach back and turn on the valve - even though his hands are full of expensive equipment

If the diver fails to immediately and correctly identify the problem and successfully employ the correct resolution with empty lungs and crushed ear drums, this could end very badly.

It is NOT a low stakes situation and it is NOT a necessarily trivial situation to extricate yourself from. Sinking out of control with nothing to breathe is a lot different than talking about turning on a valve on the internet. The complexities of this situation has caused people to die.

It is very important that people can reach and turn on their own tank valve, but the objective should be to never have to actually do it.

edit: This is one of the scenarios which makes me so nervous about people who "casually" will wear no ditchable lead. If they jump in with the tank off and swim down a ways, their options for making it home that day are significantly reduced.

 

[Centrals]

The question was: should you turn the tank off after turning it on and checking it.

It is all depend on the situation.
I usually turn on the gas twice;
1. The initial setting up and then turn it off.
2. Self/buddy check just before the slash.

 

[Dan]

You should carefully consider this assumption of "the stakes are not high". I would argue that the stakes are very high, in fact the diver may well DIE if they don't accomplish the task. You might feel the problem is easily fixed, but that does not mean that the stakes are "not high".

This is not a trivial point or semantics. What you may not realize is that some divers enter the water in a negative condition and may immediately begin a head first decent and some (advanced) divers might even consciously avoid inhaling deeply in order to stay as negative as possible for the first 10 or 25 feet of descent. So you could easily have a diver who is swimming down hard, sinking fast, takes a breath from the regulator, slowly exhales and now is even heavier and is 35 feet down and then pops his inflator a little and then tries to clear his ears and simultaneously tries to inhale and there is NOTHING. Nothing to breathe and there is no immediate solution to the negative buoyancy situation.

So now the divers is sinking, is heavy, his ears are hurting enough to be a huge distraction and will soon be subject to barotrauma and if he delays for 3-4 seconds more before figuring the problem out - his ear drum will rupture and now has to make the decision to
(a) drop weight,
(b) swim up like hell,
(c) locate his buddy and communicate the problem and secure a second stage
(d) locate and then switch to his octopus - obviously a bad decision in this scenario, but one that a diver might try in an emergency
(e) TRY to reach back and turn on the valve - even though his hands are full of expensive equipment

If the diver fails to immediately and correctly identify the problem and successfully employ the correct resolution with empty lungs and crushed ear drums, this could end very badly.

It is NOT a low stakes situation and it is NOT a necessarily trivial situation to extricate yourself from. Sinking out of control with nothing to breathe is a lot different than talking about turning on a valve on the internet. The complexities of this situation has caused people to die.

It is very important that people can reach and turn on their own tank valve, but the objective should be to never have to actually do it.

edit: This is one of the scenarios which makes me so nervous about people who "casually" will wear no ditchable lead. If they jump in with the tank off and swim down a ways, their options for making it home that day are significantly reduced.

This is one of many reasons I carry Spare Air.

 

[johndiver999]

And while I am ranting - if we want to discuss the scenario to follow if the tank does not provide air on descent and the diver has already descended to some non-trivial depth before the problem is manifested, then what about the situation where the diver is sinking, can't inflate the BC and decides to just allow himself to sink and fully concentrate on turning the valve on.

What happens if he then finds that the valve IS already on? What if there is an obstruction in the tank or regulator which has suddenly caused air flow to stop (even though the valve is opened)? Or perhaps the tank is simply MT. What now? If there is no buddy to provide assistance immediately, the only solution is to swim like hell (and also possibly drop ballast).

So I think my solution to getting no air after descending several feet would be to switch to my pony and head directly to the surface. Once there I can blow up the BC orally and then check the tank valve. I really don't want to be doing that while sinking if I can avoid it.

Running for the surface is not always the best decision when problems happen, but if I am not too deep and I can get to the surface quickly and easily, I would prefer to deal with serious problems at the surface.

 

[MaxTorque]

I think the main thing to take away from most of ^^ that, is that a water entry in a significantly negative condition is really, really to be avoided, because it gives you no time to sort an issue.

 

[BRT]

I think the main thing to take away from most of ^^ that, is that a water entry in a significantly negative condition is really, really to be avoided, because it gives you no time to sort an issue.

But sometimes that is the best way to go in.

 

[Jake 10]

Set up and check everything. Then turn it off and depressurize regulator/octo. Then turn on when putting equipment and strapping BCD.

 

[johndiver999]

But sometimes that is the best way to go in.

I do a lot of "negative" entries for drift diving, but if you are willing to just flip over, swim straight down head first, you can get pretty deep quickly and there is no need to be excessively negative. In fact, as long as you are neutral or close to neutral, you can descend pretty easily if you kick down hard until you get some wetsuit compression (and any residual air in BC is compressed) at 15 or 20 feet, then you can reduce kicking and fall vertically - assuming that is something you want to do.

 

[kelemvor]

it's a requirement for all of my new divers. We get them in the habit that as soon as they descent they go horizontal and manipulate their tank valve to make sure it's all the way open, then as they are close to the bottom they will tighten their waist belt and weight belt since everything has shifted. It's a good habit to get into. I've seen well meaning but green dive masters check tank valves and actually turn them most of the way off before, so it's always a good thing to make sure it's all the way open.

Vindicator handwheels are a good solution for this. It becomes extremely obvious if the air is on or not.
$16 solution to other people's skills problems. Shopping Categories Piranha Dive Shop |

 

[emoreira]

I open the tank valve, see the tank pressure, test seconds, hear if there's any leak and close the tank valve without purging. I re-open it before donning the BCD. Previously I see if the SPG shows a loss of pressure.
Remember that the valve o-ring comes with the tank, which is given by the Operator. If it's a DIN reg, then the oring is yours, but the tank valve is still of the Operator.
Tank valve o-ring to regulator is often the main reason of leaks.

As mentioned before, if the diver cannot be sure if he had opened the tank valve, then this sport is not for him.