Tank valve opening procedure

[padudle]

Lately I've seen some references to different opinions about the best procedures for opening tank valves. The traditional belief is that you should open the valve all the way till it stops and then back a quarter turn. More recently some are suggesting that it is better to simply open the valve all the way.

The argument for backing off the valve is that the valve is susceptible to damage if it were to be struck in exactly the wrong way while all the way against the stop.

The argument for opening the valve all the way involves the possibility for human error. Apparently it has been documented a few times that people have made the mistake of turning the valve all the way closed then opening it a quarter turn. At the surface the regulator breathes correctly and the pressure gage shows full. As the diver descends however, the valve may not be open enough to supply the increased air demand at depth. This can cause an immediate out-of-air condition or just very hard breathing.

When I took my certification several years ago our instructor taught the traditional technique but mentioned that the subject was under debate and explained the arguments both ways.

I lean toward having the valve either fully open or fully closed to minimize the chance of human error. My understanding is that newer tanks generally have rubbery valve handles that reduce the chance that an impact will damage the valve.

Is there a consensus on this matter now?

Please advise.

Pete Dudley
Albuquerque, New Mexico, USA

 

[Wayward Son]

Is there a consensus on this matter now?

Nope, it gets argued on a fairly regular basis.

I do it the old way, I open the valvel fully & then close it about 1/4 turn. Just a bit so it's not fully stopped. But I've been doing it that way for over 30 years, so what do I know?

Valves being stuck open may be less likely now than in the past, I dunno. But I see no harm in doing it this way so I do.

 

[redacted]

I open it all the way and then make sure there is no pressure on the opening "stop". This usually involves closing it ever so slightly.

 

[Walter]

All the way open does not decrease human error. It may even increase it.

 

[crlavoie]

I was always taught to open it and then back it off about a 1/4. However, what's interesting is that it's not just for SCUBA tanks. You will see that plumbers and mechanics (hydro, HVAC, auto etc.) do this as a standard practice.

 

[wardric]

I was taught to open the valve all the way till it stops and then back a quarter turn and since i've been doing that for 12 years, I do the same with many things now like my propane grill tanks

 

[MikeFerrara]

All the way open does not decrease human error. It may even increase it.

Except that if it's all the way closed you'll know it. If it's all the way closed and then turned on part of a turn you may not until you have trouble getting gas or reach back and check...and of course many divers can't reach their valves.

A scuba valve is designed to be an on/off device. We don't use it to control flow as we do a reg. Functionally, there are two valid positions all the way on and all the way off. Any place inbetween and you just don't know for certain which you'll have at depth and it can even vary from one valve to the next because x number of turns does not equate to a known orifice size or flow capability. If it's only 1/4 of the way on, it can be a real problem for the divers who can't reach their valves. Some valves will go from full open to full closed in a little over one turn and some require several turns. the result is that 1/4 turn will not have the same results in all valves. Besides that, one persons 1/4 turn may not be the same as anothers.

I

 

[texdiveguy]

In the sport diving side the 1/4 turn from full open is most common,,,,in the tech side of diving full open is the method usually taken. I prefer full open.

 

[speedhound]

I open my valve all of the way, and then close it by a quarter-turn. As as Engineer I was always told to do it this way to help prevent a valve from jamming open. In the event that a (non-diving) valve does start to stick, you know that the valve should be able to move both ways to help free it up.

Likewise with a (non-diving) valve I tend to close them gently, and only "nip" them finger tight. I've known too many tool-wielding gorillas wreck valves and pipe systems by being overzealous.

 

[drbill]

You mean you're supposed to open the valve before going in the water? I wondered why I got so many short dives out of a single tank!

I've heard that the open then quarter turn method was due to the construction of early brass valves for high pressure applications. It was my understanding that modern valves do not require this. However, I'm a creature of habit so I do the full open, quarter turn back as I've been doing for 45 years now. You just can't teach an old dog new tricks.