Stage Bottle - On or Off?

[ding dang]

I did a brief search to see if someone had asked this before, but couldn't find anything.

When you sling a stage bottle, do you keep the air on or off?

On my AOW deep dive, they hung an AL80 @ about 15 feet for emergency - they turned the air on to fill the hose, and then turned it off, but didn't purge it. They explained that the water wouldn't be able to get in the tank because of the air pressure in the hose.

So, if you don't do this, and you keep the valve off underwater, can water somehow seep inside?

What's the proper procedure?

Thanks

 

[ianr33]

Off.

Pressurize it on the surface,check spg every so often. Repressurize if the second stage has been knocked and accidentally purged.

 

[Cave Diver]

Bottles that you're going to drop somewhere and leave, I do what Ian recommends. If the bottle has a leak and you leave the valve on, you may come back and find it empty.

On deco bottles that I'm taking with me, I do the same. We turn them on when we are getting ready to switch to the deco gas and verify we have the correct bottle.

My CCR bailout bottle that I keep with me stays on. If I have to switch to bailout gas, I want it, and I want it NOW and I'm not wasting time turning on a valve to get it. Plus, on CCR if you did have a leak on an OC bailout bottle you're much more likely to hear it.

 

[AndrewA]

I do the same as Cave Diver. Any "stage bottle", whether on a line or carried by me, is pressurised and then turned off. This avoids accidental gas loss. (remember to brief any divers on the dive that they will need to turn on any cylinder left on the line).
When I use a back mounted "pony" I leave the valve open, this is my alternative air source and in an emergency I dont want to have to turn it on.

 

[Sas]

I do the same as Cave Diver, AndrewA and ianr33. Just don't forget to turn it back on when you switch. I forgot that once :\ (in a course too, how embarrassing).

 

[TSandM]

Pressurized and off. You do need to check the pressure frequently, because if it depressurizes, it is very possible to get water into the first stage, and it will ruin your pressure gauge.

 

[Scott L]

Pressurized and off. You do need to check the pressure frequently, because if it depressurizes, it is very possible to get water into the first stage, and it will ruin your pressure gauge.

Is this less a concern with piston first statges?

 

[TSandM]

I don't think it matters . . . if the seal between the first stage and tank fails (and it is dependent on pressurization) the first stage can entrain water. The water will get carried downstream with the gas. The first stage will need service, as may the second stages as well, but the SPG will be ruined. I unfortunately have personal experience with this . . .

 

[spectrum]

Watch out for Sherwoods, most of which have the dry bleed feature. That will deplete the hose contents fairly quick.

Pete

 

[mikeb663]

A piston first stage will better tolerate flooding. You are correct that more than likely the SPG will need to be replaced. I use piston first stages on my stage/deco bottles for this reason. I describe the piston to be more tolerant of flooding because they have larger orifices and are more likely to remain operable after flooding.