Changing Tanks Underwater?

[jamiep3]

Another plus for those new regs with automatically sealing 1st stages?

 

[rocketry]

Common Sense & equiptment knowledgeTold me this was impossible, but then again, I wouldnt put ANYTHING passed an experienced diver

 

[stevetim]

http://www.scubaboard.com/showthread.php?t=150417
This is on the boards already. More responses here.

 

[miketsp]

..snip..
Is that possible? Short of having an entire apparatus (tank & regulator both connected underwater) I always thought this was impossible. I had asked him if he had had a regulator attached to the extra tank he had planted the night before, and his response was "no" (I, being a scared newbie, did not harp on the topic any further). It seems like water would flood the first stage and ruin the reg for that dive (this is taught in the first OW pool session!, no water in that area!). Would the prescise alignment of air bubbles make this possible? Your insight would be appreciated. While I would never even THINK of trying this, I am trying to discern scuba fact from scuba tall-tale.

Yes it is quite possible and is a standard item of the advanced training at a couple of LDS I know. When I once asked them if the regs swapped UW needed immediate servicing their answer was no, provided the reg sets are well purged after the exercise.
During one of the exercises you get to the corner of the pool, find a tank with a reg (off) lying at its side. You have to breathe off the tank, then mount the reg, purge it & then breathe off it then leave it and move on to whatever awaits you at the next corner.

 

[TheRedHead]

Sounds liked staged deco the hard way! :lol:

 

[sharkattack]

Regulators are pretty robust

 

[rocketry]

Regulators are pretty robust

That is a good point, however all gear has limits. I gather this sort of thing is (1) dangerous when uncontrolled (with the exception of a controlled pool setting) (2) not a very favorable solution but, nonetheless (3) possible.

 

[sharkattack]

That is a good point, however all gear has limits. I gather this sort of thing is (1) dangerous when uncontrolled (with the exception of a controlled pool setting) (2) not a very favorable solution but, nonetheless (3) possible.

Would I do it? No way in hell, but it wouldn't damage the reg in any way as long as it was disassembled, cleaned, dried, crystal lubed, reassembled, IP checked, and tuned.

 

[miketsp]

..snip..
will probably screw up your spg, but it works.
..snip..

Your SPG is nothing more than a spiral tube which expands when pressurized. With or without water inside it will read the same.
You may however reduce its life a little due to corrosion if any water gets in.
However for this exercise I was taught to hold the second stage purge pressed while opening the tank valve slowly to avoid creating any undue stresses in the system and to let any water purge through easily with lower pressure while pressure is building up.
In practice very little water actually gets into the 1st stage as the air inlet filter tends to trap an air bubble inside the 1st stage.
Note that the hose to the SPG has a very small pinhole and in practice water prefers the path of least resistance. The spg is also a closed circuit so after the flow required to pressurize it the flow stops. If I had to do it with my own reg I'd probably unscrew the hose from the SPG at the swivel afterwards just to check for any water ingress.

 

[ScubaMike14]

Not sure why this thread is such a big deal. Of course you can change a tank underwater, and quickly purging the second stage will blow out any water that get's between your reg and the tank.

When you really think about it, it's nothing more than 1/4 teaspoon of air space anyway. Not much water, if any, will enter the first stage when disconnected, if done quickly.

Mike Rushotn