Tank orientation

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Back mounted pony bottles are often mounted valve down to allow easier access to the valve. As others pointed out, underwater its all relative.

Topside, you typically needs something to protect the valve if its on the bottom, if its on top it needs nothing. Simpler is better most of the time.
 
Originally, SCUBA gear was radically different and pretty much required tanks to be valve up when diving. the original recreational setup, the "Aqua-Lung" was a very primitive first stage that had a single corrugated hose attached at two ends of the stage with a mouthpiece in the middle to breathe from. the corrugated hose circled the divers head and the mouthpiece was an integrated one-way valve. The air came down the hose on your right, then continued up the left hose until your bubbles came out behind your head. This setup made it pretty difficult to orient the tank downward, unless you customized some reeeeeally long corrugated hoses to go up to your head, and that would be very impractical. When the "modern" first and second stages were developed, nobody thought to turn the tank upside down because "that's the way it as always been" syndrome caught on. That's actually why second stage hoses come around your right shoulder, because that's the way the Aqualungs were set up.

When I get back into tech, I'm totally inverting my doubles. All you need is a 9 foot hose instead of a 7 foot, and it's way easier for me to scratch my butt than grab my shoulder blades!
 
I think it comes down to the lowest common denominator, money. Recreational diving gear is expensive so given the choice between an inverted tank with a cage to protect valves and regulators and longer hoses, and the setup we most commonly see I think most divers will chose the less expensive option an inverted setup may well be more functional but it is also going to be a couple of hundred bucks more expensive.....
 
Originally, SCUBA gear was radically different and pretty much required tanks to be valve up when diving. the original recreational setup, the "Aqua-Lung" was a very primitive first stage that had a single corrugated hose attached at two ends of the stage with a mouthpiece in the middle to breathe from. the corrugated hose circled the divers head and the mouthpiece was an integrated one-way valve. The air came down the hose on your right, then continued up the left hose until your bubbles came out behind your head. This setup made it pretty difficult to orient the tank downward, unless you customized some reeeeeally long corrugated hoses to go up to your head, and that would be very impractical. When the "modern" first and second stages were developed, nobody thought to turn the tank upside down because "that's the way it as always been" syndrome caught on. That's actually why second stage hoses come around your right shoulder, because that's the way the Aqualungs were set up.

When I get back into tech, I'm totally inverting my doubles. All you need is a 9 foot hose instead of a 7 foot, and it's way easier for me to scratch my butt than grab my shoulder blades!

You mean this, surely you jest:

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Most of the guys are diving a USD Phoenix RAM HPR (US Divers Phoenix Royal Aqua Master High Performance Regulator). Mine has a cracking effort of only .3 inches, try that with your single hose. A few of the guys are diving prototypes of the Argonaut HPR. "Primitive" my arse.

N
 
Uh, Nemrod, you know that the phoenix nozzle was invented as a way to modernize the aqua-lung right? You got yours through Vintage Double Hose? That's where I got the parts for the DW Stream Air I dive on occasion. No Phoenix, I have a J valve and a wrist mounted depth gauge. The system your diving is a mashup of the old beauty and the new safety.

When the Aqua-Lung first came out they were primitive as all get out. You had to check your air and calculate how much time you could be down and then stick to a profile. you had to buddy breathe by shoving the mouthpiece at your buddy and hope he didn't panic, which he often did. When you ran out of air you activated your J valve and swam up, assuming that a stray bump didn't activate it during the dive sometime. Maybe you wore a Mae West for buoyancy, maybe you just swam down and swam back up again. Or you weighted yourself to be negative and were could tell your tank got low because you were floating instead of sinking.

Modern first and second stage rigs make diving a lot safer hands down. Now, do they force the diver to be more in tune with his environment, becoming Cousteau's "manfish"? I don't think so. that's why I enjoy diving my double hose, it keeps me on my toes. Plus I enjoy explaining what it is to divers who stare at me.

N, is the Octo bungied around your neck? Why is that?
 
SCBA and SCUBA have a difference of a U which stands for Underwater.

:) I am being cheeky, yes I am :eyebrow:

mostly I have seen the inverted ones with Rebreathers and like you mentioned with a casing - but then again they are smaller tanks.
 
Commercial divers always have the tank valve down when it is being used as a bail out bottle so they can reach the valve. The reason is the bail out bottle is not turned on until needed so air cannot accidently drain out during the dive and end up being empty when needed. I have never seen or heard of anyone using a cage around the valve and that would cause more problems than it is worth. There are no good reasons why you cannot do this if you are more comfortable doing it that way.
 
Can't say that I'd be comfortable with an inverted tank, but that's just due to my specific experiences. I, too, have lots of time in SCBA units (fire and rescue) and in that scenario I'm okay with it. However, I'm one of the "lucky" few that have had a "situation" underwater in which I inverted and junk in the rental tank blocked the first stage. Evidently, the internal snorkel was missing or broken off. Since then, I'm much more careful about tank orientation. I still invert, but I'm always just a little conscious of the possibilities. I think having a tank that spent a great deal of time upside down would be worrisome for me, even though I logically know that the chances of that happening again are extremely remote.
From a practical standpoint, the longer hose issue appears moot, except in the case of the inflator hose. On my rig, that would mean the hose from the first stage would be coming from the wrong direction. Not insurmountable, but inconvenient. There's actually little about an inverted rig that would make it impossible, though.
 
most people in the uk invert the tanks because they cannot reach the valve when it is right way up.
 
https://www.shearwater.com/products/teric/

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