Empty or Full tank to check properly being weighted?

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Mtbr

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What's the proper procedure to check if I'm weighted properly?

I know the rule of thumb is to be able to hold my breath while floating with water level near my eyes, but am I suppose to do this with a Full tank or at the end of my dive when I have roughly 500 psi left?
 
Empty, assuming an aluminum tank. You want to be weighted so you're neutrally bouyant at the end of your dive (that's when your tank will be positively bouyant). If you weight yourself to be neutral with a full tank, you'll have a tough time staying down at the end of the dive (safety stop).
 
Empty, assuming ANY tank.

A steel tank does not magically make up for lost density as you use up air. Loss of mass is loss of mass.
 
I do the buoyancy test at 20', 500PSI, no air in my wing. IOW under safety stop conditions.

In theory, the surface method doesn't take into account that buoyancy of your neoprene, which depending on it's thickness, could keep you floating at the suface but make you a little negative at 20'. Whether or not it makes that much difference I don't know. Probably not, but I do it at 20 feet anyway.
 
Mtbr,

Remember that the objective is to always be in control of your buoyancy. You can make up for a little extra weight with air in the BC but if you are under weighted you will be looking for an anchor. If you cut things to close on weight you will find it difficult tor impossible to make a slow gentle final ascent.

Remember to set your weight so that you bob vertically at eye level at the end of your dive with an empty BC, an average breath, your feet still (crossed) and about 500 PSI in your cylinder. A deep breath should get your mask out of the water and a deep exhale should sink your mask. Do all of this while breathing from your regulator. The end of the dive is the defining moment for your weight requirement and you want just enough to let you stay down in the shallows with a light cylinder.

You can make the same test pre-dive with a full cylinder and add 5 pounds to compensate for the buoyancy gain you will experience as you breathe the tank down. Be sure to repeat at the end since you are apt to have some stowaway buoyancy (trapped air) in your gear early in the dive. You are safer being two pounds heavy than 2 pounds light.
 
I do the buoyancy test at 20', 500PSI, no air in my wing. IOW under safety stop conditions.

In theory, the surface method doesn't take into account that buoyancy of your neoprene, which depending on it's thickness, could keep you floating at the surface but make you a little negative at 20'. Whether or not it makes that much difference I don't know. Probably not, but I do it at 20 feet anyway.

The surface method is intended to take into account the neoprene such that you can make a gentle final ascent. Also when shore diving considerable time may be spent in the shallows when the cylinder is getting light . If you're neutral at 20 feet the shallows won't be a lot of fun.

Pete
 
I do the buoyancy test at 20', 500PSI, no air in my wing. IOW under safety stop conditions.

In theory, the surface method doesn't take into account that buoyancy of your neoprene, which depending on it's thickness, could keep you floating at the suface but make you a little negative at 20'. Whether or not it makes that much difference I don't know. Probably not, but I do it at 20 feet anyway.
I don't know the origin of this "safety stop" buoyancy check thing, but its endurance was solidified by its inclusion in the NAUI Advanced Open Water Diver manual about 15 years ago. It was a bad idea when it started and is still a bad idea today.
Even today's open water books can easily leave one with the idea that the dive is over at the end of the safety stop.
It isn't.
The most critical portion of the ascent, from a decompression sickness standpoint, is the final few feet, where the change in pressure per foot of depth relative to the ambient pressure - and consequently the largest potential for bubble growth - is greatest. Precise buoyancy control all the way to the surface is important, and if you do your buoyancy check at safety stop depth and are wearing a dry suit or any neoprene at all you guarantee you'll be positively buoyant for the final few feet of ascent - not good.
Don the rig you're going to dive and do the buoyancy check with a near empty tank at the surface, in a pool, before diving that rig. Then if you're headed for salt water, add 2½% of your total weight (total weight is you, your tank, BC, reg, suit, accessories, weights, everything) to achieve neutral buoyancy.
:)
Rick
 
https://www.shearwater.com/products/teric/

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