Posted by Kendall Raine on June 20, 2002 at 11:56:00:
In Reply to: Tank position posted by Ed L. on June 18, 2002 at 19:27:47:
Backgas tanks aren't mounted upside down for several reasons:
1. Mounting upside down exposes the valve and the regulator to potential damage.
2. Mounting upside down requires a longer hose than mounting right side up. Even using a long hose (e.g. 7'), you would need a longer hose to accomplish the same thing.
3. Risk of damaging the regulator and valve in the upright position is much less than inverted if you know how to dive.
4. For those who use an isolator manifold, accessing the isolator valve with inverted tanks would be a more difficult and expose the isolator to extreme risk of damage.
5. You can easily reach the valves on a tank mounted rightside up if the tank is mounted properly.
6. I've never tried something so silly, but inverting the tanks should change trim, as well. The heaviest part of the tank is the top-particularly when the tank is near empty. Pushing weight back tends toward pushing the hips and feet down. You want to swim hips level with shoulders and feet up. This is a minor reason relative to damage, however.
Argon bottles are mounted upside down because they're small and the only way to reach the valve is if it's inverted. The same would be true for ponies if one were into that contrivance.
SCBA bottles that firemen use are mounted upside down because they are generally smaller than scuba tanks and the risk of damaging the valve while running through a burning building in zero viz is much higher than the risk of damaging a scube valve while swimming (or scootering) through a wreck or cave.