Apeks ATX 200

[water+cam+guy]

I am in the middle of doing my DM course...The other night in the 12 ft deep pool, I was on my back blowing bubbles as I killed time... I could not help but notice that the breathing was VERY hard and laboured coming from the 2nd stage. I dialed it down, but then had a wicked freeflow at the surface. Is there anything about the orientation of the second stage in the water column as it relates to the cracking pressure?

 

[coldwaterlloyd]

If opened up it will free-flow on the surface , I usually detune it down if I am not breathing off it . All Apeks are sensitive if wide open on the surface. Yes , if tuned down it can be hard to breathe at depth. Once you open it up a little it is effortless .

 

[water+cam+guy]

True... I should have added, that on my back, the breathing was labored...as I flipped around to my stomach, and trimmed out, the breathing was fine. Hence my question about orientation in the water column in terms of sensitivity

 

[LGH]

I have noticed the same thing not only with my own DST/XTX setup but also with Aqualung and Scubapro regs. Actually this has always occured in the pool - never in the sea - but then again, that might not be too strange considering I'm seldom on my back taking a nap at the bottom of the ocean floor. :-/

 

[Fishpie]

Here comes Nemrod with a nice diagram for you.

 

[rigdiver]

Think about it: Horizontal and face down = more water pressure on the diaphragm = easier to breathe. Face up = less water pressure on the diaphragm = harder to trip the 2nd stage valve into delivering air. A well tuned regulator will free-flow if placed in water with the diaphragm first.

 

[beanojones]

Here's the biggest deal though. The pool is shallow. The Ocean is deep.

Since you are taking the DM course, you get to reason things out from those statements. What I said is very important, and in the end, it is all you need to know to explain things. Well that and some basic physics. As with most physics, rate of change matters more than absolute measure.

The answer to this question is also the answer to why AGEs are more likely to occur in a pool than the ocean.

 

[Couv]

As Rig Diver pointed out, when laying on your back with a single hose regulator, the second stage is subjected to less pressure than your lungs and diaphram. Just like breathing through a long snorkel.

I stole the diagram below from Luis and Nemrod