Dumping Air Under Water

[Litefoot]

On a wing, I've read that it is better to dump air from the bottom left dump valve instead of the inflator purge. How efficient is the dump valve versus the inflator? I know the dump valve is on top of the wing if you're diving horizontally, but is it also necessary to be head-down to get a full dump? When I was in a pool practicing last weekend, I was at about 12' working on buoyancy. I had added a little air, but when I pulled the dump valve string, I felt like nothing came out.

If you dump air with the inflator purge, it seems to introduce water into the bladder. Does that create weighting/trim issues over the course of a dive?

 

[RyanT]

The little bit of water you introduce to the wing isn't going to make any noticeable difference during your dive.

In good horizontal trim (e.g. nice and flat), it's often a little easier to just tip into a slightly head-down orientation and vent from the bottom. As you discovered, however, if you are slightly head up, the air in the wing will be at the top and the bottom dump won't vent anything. When I need to vent, I just use which ever one best suits my position in the water at the moment.

 

[Angelo Farina]

Underwater, water has no weight, so the water entering the bladder does not cause any significant buoyancy or trim issue during the dive. When raising the tank on the boat, you feel the additional weight...

 

[Zef]

The dump valve is on the bottom of the wing (toward the diver) when horizontal.

For some, including me, it takes a bit to figure out the body position to get air to come out of the dump valve. You don't need to be head down but need to slightly roll your left hip up....when I first migrated to using the dump valve I kind felt like I had to jut my butt up a bit. Eventually the position becomes second nature and you stop thinking about it.

For me, and those that recommended to me to use the dump valve instead of the inflator hose, I have more control over how much air I let out.

-Z

 

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I add shoulder dumps to all my wings

The fastest safest way in an emergency

 

[Wibble]

The shape of the wing matters. If it's a horseshoe wing, e.g. shaped like a ∩ with the dump in the bottom left, it may be that the air has moved to the right-hand side.

If you tip over to the right, such that the RHS is lower than the LHS, you may hear the air migrate from right to left and you can dump.

The other type of wing is a "doughnut" which has a path between the two sides on the top and bottom. This doesn't suffer as much from the air gathering in the wrong side.

 

[BRT]

I haven't dumped air with my inflator hose for at least 25 years.

 

[Doc]

I haven't dumped air with my inflator hose for at least 25 years.

Wow, it must be getting pretty full by now.

Oh, i get it, never mind.

 

[rongoodman]

You should be able to feel the bubble of air under your hand when it's on the dump valve. If you can't, go a little head down.

 

[RyanT]

You don't need to be head down but need to slightly roll your left hip up.

Yep, forgot to mention the little roll, also very helpful.