Why isn't there a tank valve-open marking?

[Javik]

Due to the occasional apparent confusion about which way to turn tank air valves to open them, and the possibility of air being turned off by inept dive boat crew, etc, why isn't there some universal labeling standard to show which way to turn a valve on?

It would seem relatively simple to have an arrow molded into all valve handles, and the arrow points in the direction of Open / On.

This way even if for some reason a valve is breaking the standard CCW-open method, it's obvious just by looking at the arrow direction what needs to be done.

 

[Milkman670]

Vindicator Valve Knobs

 

[RainPilot]

Ive never run into a valve that wasn't righty-tighty lefty-loosey. Even if there were markings, I doubt it would would make a massive difference to the incident rate. The Vindicators that Milkman linked to, otoh, are a really useful thing. Instant visual confirmation.

Another tip, the "open all the way then half turn back" is a dangerous, outmoded technique that has killed and nearly-killed numerous divers. Open all the way then leave it there.

 

[Patoux01]

Another tip, the "open all the way then half turn back" is a dangerous, outmoded technique that has killed and nearly-killed numerous divers. Open all the way then leave it there.

Mostly it's "quarter turn back", but yeah, ditch that crap. However, don't open a valve "like crazy" or it'll be sticky open which is annoying if you have to shut it down. Open them gently all the way.

Also, on my valves at least, there is a small arrow saying "open". It's on the side however. But otoh, if you turn right you close, turn left you open.


Finally, last solution: be responsible for your own safety and don't let someone else touch your gear. If that useless guy that checks valves before you jump in from a boat goes "Oh, your valve was closed, I opened it", I know I'd go back, sit down, take the tank off and check it myself again. Not his choice to be there I guess, but it's my choice to not want someone doing that for me. Otoh, I dive sidemount, so I just rest my hand on the valve while walking to the back of the boat, that way I know for a fact he will not touch it, and if he insists I'll simply turn it back the way I want it. This got me in an argument with an instructor when I was just 6 dives old, before my first AOW dive, so you may not want to do that, as I was then stuck with those guys for the next 5 dives and it kind of sucked balls.


Edit: I'll add as disclaimer, I'm a strong proponent of natural selection.

 

[AfterDark]

Ive never run into a valve that wasn't righty-tighty lefty-loosey. Even if there were markings, I doubt it would would make a massive difference to the incident rate. The Vindicators that Milkman linked to, otoh, are a really useful thing. Instant visual confirmation.

Another tip, the "open all the way then half turn back" is a dangerous, outmoded technique that has killed and nearly-killed numerous divers. Open all the way then leave it there.

RainPilot never heard of "open all the way then half turn back". I have been using the "open all the way then back it off the stop a hair" for 46 years without incident. I can see where the "open all the way then half turn back" could be trouble. Where did you that come from?

Backing valves off the stops is common practice in industries where high pressure gas is used. It's a safety issue, if the valve is open to the stop too forcefully there is a chance it may become stuck open and not be able to be closed in an emergency (non-diving emergency like a cut acetylene hose in an enclosed space) this practice was carried over to diving and then has apparently been misunderstood by many to mean 1/4 - 1/2 turn. In reality it's not even an 1/8 of a turn. A few degrees is probably a better way to measure it.

OP if you can't be sure on your own then the Vindicators are just what you need.

 

[barth]

OP if you can't be sure on your own then the Vindicators are just what you need.

Just find a way to remember what is open and what is closed or practice until you know it.

Vindicators is not the solution for the problem. What when you rent a tank without vindicators or use somebody else his tank without vindicators ?

I check the valve(s) if they are open or closed before I enter the water. At that moment it is not possible to see vindicators.

 

[Neilwood]

The only 100% sure way to do it is a breath check right before entry - breathe it and see if the needle moves on your SPG.

Not sure if markings on the valves themselves would work - hard to see after a bit of abuse. The vindicator knobs are a good idea though.

Personally I would rather no one touches my valves but me - that way if my valve is off there is only one possible doofus that did it.

 

[Storker]

I have been using the "open all the way then back it off the stop a hair" for 46 years without incident.

I have been handling compressed gas bottles on and off for more than twenty years and this is how I've always done it. I don't see any reason not to do it the same way when I open my dive tank valve. Ramming the valve to the stop seems like a pretty unsafe practice.

And neither I have ever heard of valves that open when you turn them right.

 

[Bob DBF]

...this practice was carried over to diving and then has apparently been missed understood by many to mean 1/4 - 1/2 turn. In reality it's not even an 1/8 of a turn. A few degrees is probably a better way to measure it.

I believe this is yet another "teach by catch phrase" rather than understanding what you are doing and why.

Valves that do not have a backseat, which are most, should not be forcefully opened or left open against the open stop because it it may damage the valve and/or jam it. Gently opening the valve fully and backing it off the stop slightly as AfterDark described, as well as my previous training on valves, protects the valve and insures it is open and will continue to operate properly.



Bob

 

[Patoux01]

The only 100% sure way to do it is a breath check right before entry - breathe it and see if the needle moves on your SPG.

Depending on the depth you're looking at, I'm not sure that actually works. I'd have to do a test if I ever get to dive deep-ish (100' +), but I wouldn't be surprised if you can have it open "enough for the needle not to move, not enough for you to get air at depth".