Pull Dumps — lose them

[oldschoolto]

The fact this incident involved an instructor is very troubling. Assuming he was diving a single tank and was unable to keep his head above water is even more troubling. My wing is completely empty when I start a dive (negative entry), but more importantly at the end of a dive when I surface. If you can’t swim a single tank up to the surface and stay up for any length of time without an inflated BCD you are probably carrying too much weight.

That's old school diving.. Get with the newest and greatest Scuba.. Where ANYONE can be a diver or a instructor for that matter..
Jim..

 

[kelemvor]

I was thinking some more about this issue and had almost forgotten something important. When I first got my wing with a pull dump, something about the setup left it being far too easy to pull and thus sometimes dumping air when I didn't want to. Temporarily I extended the internal wire that connects the inflator to the dump mechanism by adding another wire. Then I ordered a proper replacement. It's been long enough that I don't remember how much I paid - probably too much since I got it through my LDS.

My point is, if you're inadvertently dumping air then maybe you also have this problem of too short a dump wire.

 

[oldschoolto]

I believe that the pull dump wire was added to control a runaway inflator... Don't try a fix a problem that's not there..

Jim
.

 

[Umuntu]

I believe that the pull dump wire was added to control a runaway inflator... Don't try a fix a problem that's not there..
.

I'm not sure I understand what you intend. The wire is not actually connected to the inflator valve. It cannot stop the inflation of a BCD.

 

[CuzzA]

So far the take away from this thread is all neglected gear has a higher failure rate.

The connection of the corrugated tube to the BC is essentially the same whether it is a pull dump or not. They are after all interchangeable. This is the likely failure point, that and the connection at the inflator.

Of the incidents that have occurred, it appears user error has been the main factor. Pretty common in diving accidents.

As kelemvor pointed out, too short of a corrugated hose could lead to an issue, especially if someone has long arms.

On my singles rig there is a pull dump with an air2. When I added the air2 I extended the length of the corrugated hose to give my head full range of motion in a rare buddy diving air sharing situation. I've never experienced an issue with inadvertently dumping gas. I also am very familiar with my rig and know it like the back of my hand. I simply can't see it happening to me. It takes some effort to pull dump.

Of course the other glaring point here is can you swim up your rig without the assistance of a bc? If not, it's time to reevaluate your setup.

 

[MXGratefulDiver]

I once experienced the opposite problem. Had an AOW student borrow one of my rigs once. They're all BP/W with a simple elbow connection. On our first dive we surface swam out to a buoy, and when I gave the signal to submerge the kid grabs the inflator hose and gives it a yank. Naturally, nothing happened ... so he yanked harder, and pulled the hose right off the elbow. Needless to say he was suddenly negatively-buoyant and sank like a rock. Fortunately he had the sense to dump his weights, which sent him right back up. We recovered his weights, fixed the inflator hose, and completed the class without further incident ...

... Bob (Grateful Diver)

 

[The Chairman]

My point is, if you're inadvertently dumping air then maybe you also have this problem of too short a dump wire.

I have actually changed out the wire cable for mono leader. I like a really short corrugated hose, so all my cables are custom lengths to fit the hose. I use the leader material to hold all sorts of things too.

BCs can fail for a number of reasons. The take away for me is to dive with a balanced rig, or have redundant buoyancy. You shouldn’t be negative at the end of your dive if you’re balanced. If I am going to be negative, like when I wear doubles, I dive a double bladder wing. That’s either back or side mount.

 

[Capt Jim Wyatt]

Actually I did not base my opinion on this one incident. I base it on eliminating a failure point that we do not need. I have always suggested, strongly that my cave students get rid of the pull dump and the little thin rubber diaphragm that holds
the gas in the wing.

​

 

[oldschoolto]

The inflator dump valve will dump air faster than the inflator will fill the BC.. So, If you have a stuck inflator, Simply pulling down on the hose will stop your runaway accent... The low pressure hose would/should stop the BC hose from pulling off.. But then you should be taking better care of your kit if the zip ties a dry rotted...

Jim..

 

[kelemvor]

Actually I did not base my opinion on this one incident. I base it on eliminating a failure point that we do not need. I have always suggested, strongly that my cave students get rid of the pull dump and the little thin rubber diaphragm that holds
the gas in the wing.

Fair enough, and I'll state for the record that I wouldn't bring a pull dump into a cave either. The physical structure of it makes it quite a bit more of an entanglement hazard than an elbow. Different tools for different jobs. The change has everything to do with entanglement hazards and little to do with me pulling the dump by mistake or my gear falling apart. Of course you also go into a cave with redundancy (drysuit in my case) so such a failure would turn the dive, but it wouldn't be deadly unless followed by additional failures or errors.

I bring lots of gear on open water dives that I wouldn't bring into a cave. I don't think it's a fair comparison.