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Thread: why do they do this...

  1. #1
    Grouper
    Join Date
    05/24/2011
    Location
    Frisco Texas
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    why do they do this...

    been watching a lot of different diving and ocean type shows.
    was watching one on pearl divers. and another show i dont remember
    they were using short tanks but inverted.
    the valve in the small of the back

    just always assumed tanks were enginered to work right side up
    why do some divers use the inverted config

  2. #2
    Tanks work on pressure. Think about it, if I had to swim straight down through a ship wreck the tank would have the valve facing down but it still works. Essentially, a tank will work in whatever position you put it until the pressure drops below the pressure required for the regulators to work.

    When I watch firefighters they wear their tanks with the valve facing down. I know when I go to sit down on a boat I will occasionally bang the bottom of my tank. If it was inverted I could easily damage my first stage regulator, I could accidentally pinch/damage my hoses. Additionally, the regulator recover technique I learned in OW would no longer work. If my regulator got knocked out of my mouth I'd have to reach for the valve, grab the hose and follow the hose until I found the regulator. If my buddy needed my octo and accidentally dropped it when releasing it, recovering it would be a lot harder as well. Any buddy I had would not be familiar with my gear configuration. I practice from time to time with people at my shop. All that practice would be useless if I was on vacation in the Caribbean and my insta-buddy wasn't familiar with my configuration.

    These are just some of the reasons why everyone who is a typical recreational scuba diver uses the same valve facing up configuration.

    I do know that it requires a lot less flexibility to reach the valve on a tank with the valve facing down then with the valve facing up. Also, if I was going into a shipwreck or cave, I'd be less likely to bang the valve if it was facing down. However, breaking the valve off when sitting down on a boat would be more likely for most divers and pretty horrific.
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  3. #3
    Grouper
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    these folks were diiving shorter tanks
    breaking a valve bad, very bad

  4. #4
    I've seen a few videos from the South Pacific and they seem to dive short, fat tanks with a DIN connection. A lot of North American divers just get used to the Aluminium 80 cylinder with a yoke connector. It is cheaper and easier to maintain than other tanks. The standard 77.4 cu.ft. of an AL80 is often plenty for a recreational dive, especially if you dive with the 'back to the boat with 500 PSI' mentality. Additionally the aluminum tanks don't rust (they oxidize but nothing like steel rusting). So most shops will carry these tanks.

    In my area we dive fresh water (steel is fine here), there is a lot of wreck penetration, people dive rule of thirds (return to the boat with 1/3 of your air left), etc. So many dives will require more than 77.4 cu.ft. Thus you will find 63, 72, 95, 100, 108, 119, 120 and 130 cu.ft. steel tanks as well as the AL80. Some are 7.25" diameters (like the AL80) but some are 8.00" diameter. Some people will also dive the fatter tanks because they like the buoyancy characteristics of specific tanks. For example, I like the HP100 (99.5 cu.ft. @ 3442 PSI) and HP119 (123 cu.ft. @ 3442 PSI) because they are shorter than the LP108 (99 cu.ft. @ 2400 PSI) and HP120 (120 cu.ft. @ 3442 PSI).

    If I was diving shallow (40 feet or less) than an AL80 would be over kill for me. To keep the weight down I might dive a 72 or 63. I'm still going to wear it with value by my head however because anyone who dives in the Caribbean or outside of my immediate area might not be familiar with something other than an AL80. I want to dive with the same configuration someone from say Florida would be used to.
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  5. #5
    Grouper
    Join Date
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    Quote Originally Posted by scubadiver888 View Post
    Tanks work on pressure. Think about it, if I had to swim straight down through a ship wreck the tank would have the valve facing down but it still works. Essentially, a tank will work in whatever position you put it until the pressure drops below the pressure required for the regulators to work.

    When I watch firefighters they wear their tanks with the valve facing down. I know when I go to sit down on a boat I will occasionally bang the bottom of my tank. If it was inverted I could easily damage my first stage regulator, I could accidentally pinch/damage my hoses. Additionally, the regulator recover technique I learned in OW would no longer work. If my regulator got knocked out of my mouth I'd have to reach for the valve, grab the hose and follow the hose until I found the regulator. If my buddy needed my octo and accidentally dropped it when releasing it, recovering it would be a lot harder as well. Any buddy I had would not be familiar with my gear configuration. I practice from time to time with people at my shop. All that practice would be useless if I was on vacation in the Caribbean and my insta-buddy wasn't familiar with my configuration.

    These are just some of the reasons why everyone who is a typical recreational scuba diver uses the same valve facing up configuration.

    I do know that it requires a lot less flexibility to reach the valve on a tank with the valve facing down then with the valve facing up. Also, if I was going into a shipwreck or cave, I'd be less likely to bang the valve if it was facing down. However, breaking the valve off when sitting down on a boat would be more likely for most divers and pretty horrific.
    Wow. Good answers. Always thought the same thing.. why do firefighters have their tanks upside down.. but never thought through to the answer.

  6. #6
    Megalodon
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    The firefighters have their tanks valve down for the same reason most divers have valve up: to protect the valve. There's a huge risk of falling debris for the firefighter so the valve down will protect it better. I have seen a few divers have the main tank valve down with a homemade protective cage over the vlave and reg.

    I once saved a man in Wichita just to watch him dive...(inventor)

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