Suddenly no air from 2nd stage or Octo; tank at 2800 psi

[socalgalx4]

I have a MARES 1st stage, AquaLung Titan 2nd stage, and AquaLung Octo. I've done well over 100 dives with this configuration, and 3rd dive after most recent professional servicing. Today, while on the way down a wall, suddenly at 40 feet, I could not take a full breath from either 2nd stage or Octo. It was like breathing thru a straw, then having the end of the straw clamped. I breathed off the divemaster's Octo, while we ascended and aborted the dive.

At the surface, this problem didn't evidence itself at all

Am wondering...any idea as to what this problem would be caused by? It seems pressure-sensitive, but don't really care to try to re-enact on next dive. Since the only thing that links the 2nd stage and the Octo together for the same problem is the first stage, I'm wondering if this is a first stage problem.

I dove twice yesterday and didn't have a problem; yesterdays' dive was first after professional servicing by someone I've not used before.

 

[ivobj]

Most probably a first stage problem, too big coincidence 2 second stages having problems at the same time, but it is really difficult to guess, I would consider some dirt in the connection to the tank valve that caused problems in the air passage, when you disassembled probably the dirt just got out and it worked again. This is the only thing that accurs to me right now.

 

[spectrum]

Was the valve would open all of the way? Some valves have cushioning springs inline with the seal and they will shut down like cut-off regulator as tank pressure drops if only cracked. I know my Thermo Pros can do this sort of thing.

If only cracked they will also block a full fill.

Pete

 

[Diver0001]

I have a MARES 1st stage, AquaLung Titan 2nd stage, and AquaLung Octo. I've done well over 100 dives with this configuration, and 3rd dive after most recent professional servicing. Today, while on the way down a wall, suddenly at 40 feet, I could not take a full breath from either 2nd stage or Octo. It was like breathing thru a straw, then having the end of the straw clamped. I breathed off the divemaster's Octo, while we ascended and aborted the dive.

At the surface, this problem didn't evidence itself at all

Am wondering...any idea as to what this problem would be caused by? It seems pressure-sensitive, but don't really care to try to re-enact on next dive. Since the only thing that links the 2nd stage and the Octo together for the same problem is the first stage, I'm wondering if this is a first stage problem.

I dove twice yesterday and didn't have a problem; yesterdays' dive was first after professional servicing by someone I've not used before.

What you're describing is very typical of what happens when you fully CLOSE the tank valve and then turn it 1/4 turn open instead of fully OPENING the tank valve and turning it a 1/4 turn closed.

If this is the case, you would have been able to see that during the buddy check if you had breathed from your regulator while looking at your SPG. You would have seen the needle moving when you inhaled.

If you're absolutely sure that this isn't the case then I would think there is either something wrong with the tank valve (a blockage by rust, for example) or something causing a blockage in the 1st stage.

R..

 

[Anti-Hero]

It could also be a bad tank. I've read a story somewhere where a person experienced something almost exactly like what you describe, and upon inspection the tank was so full of rust that after several min. the mesh filter on the first stage had plugged up enough to restrict flow.

 

[clifftondiver]

just an echo of what was posted already, sounds like your tank wasn't fully opened. I can't wait until it happens to me!!

 

[herman]

just an echo of what was posted already, sounds like your tank wasn't fully opened. I can't wait until it happens to me!!

Look at your pressure gauge and take a few deep breaths before splashing and it never will.

 

[battles2a5]

YouTube - Sweeping SPG from partially opened valve

This has come up before. When submerged, the needle will sweep down as the pressure in the first stage is diminished, and when it bottoms out, you will get the "sucking through the straw" feeling.

 

[Diver0001]

The sweeping is noticeable on the surface before the dive as well. If the tank valve is fully open the needle will not move. If the needle moves then something is wrong.

This is the reason you're taught ni your OW course to watch the SPG while you breathe off of your primary and your buddy breathes off of the secondary.

It's an avoidable problem.

R..

P.S. Good link. Not incredibly clear but it demonstrates the basics perfectly. All closed and 1/4 turn open... needle moves.... all open and 1/4 turn closed, no movement of the needle.

R..

 

[Teamcasa]

.. I could not take a full breath from either 2nd stage or Octo. It was like breathing thru a straw, then having the end of the straw clamped....At the surface, this problem didn't evidence itself at all
yesterdays' dive was first after professional servicing by someone I've not used before.

YouTube - Sweeping SPG from partially opened valve

This has come up before. When submerged, the needle will sweep down as the pressure in the first stage is diminished, and when it bottoms out, you will get the "sucking through the straw" feeling.

If it is not a valve issue, which I believe it may very well be, return it to the shop that just serviced it. The greatest number of reg issues seem to happen immediately after some sort of "professional servicing".