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Regulator - maybe a silly question

Discussion in 'Regulators' started by Dr. Eaver, Aug 13, 2008.

  1. Dr. Eaver

    Dr. Eaver Angel Fish

    # of Dives: 100 - 199
    Location: Ocala, Florida
    38
    0
    0
    I finally got around to purchasing my own gear after years of frustrating rentals. Maybe this is a silly question, but when a regulator is outside of my mouth and ends up upside down in the water - it blasts air out until its flipped over. Why? Can that be controlled? I never really cared with the rental equipment, but my stuff should just operate better. Its really frustrating on my aux reg as it hangs upside down from a holder on my BC (it eventually stops though after messing with it and causing everyone on the line behind me to stop....) Please help with my silly question.
     
  2. 300bar

    300bar ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 5,000 - ∞
    Location:
    7,433
    105
    63
    Not a silly question,but it's what a good modern reg.does.
    Just a well adjusted cracking pressure.
     
  3. foles1972

    foles1972 Divemaster Candidate

    # of Dives: 200 - 499
    Location: Cape Cod, MA
    89
    0
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    That is pretty normal for regs of any quality. Just try to make sure the mouthpiece is facing down when you enter the water.
     
  4. Dr. Eaver

    Dr. Eaver Angel Fish

    # of Dives: 100 - 199
    Location: Ocala, Florida
    38
    0
    0
    I thought it might be. Just wanted to make sure I didn't look like a tool out there in the ocean...
     
  5. spectrum

    spectrum Dive Bum Wannabe ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: The Atlantic Northeast (Maine)
    11,376
    817
    113
    It's a combination of pressure differential and your regulator's venturi.

    If you slap it on the water, mothpiece up you apply pressure to the diapghrahm just like when you inhale. From there the venturi takes off looking for resistance, like your full lungs. Being in open air it just sputters away. Putting it in the water mouthpiece down provides the feedback to stop it.

    If you move it fast underwater while not in the mouth it will sense a similar demand and take off in a similar manner. When you put it mouthpice down it fills with a bubble of air that rises against the diapghrahm and that shuts it down.

    It's just the regulator reacting to the same stimulus as your breathing. Your earlier rentals probably were not as well tuned. By understanding this you can modify your behavior and enjoy some easy breathing.

    Pete
     
  6. SlowRain

    SlowRain Instructor, Scuba

    312
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    Not a silly question at all.

    A freeflow happens when you purge the reg or if it falls in the water with the mouthpiece facing up and is sustained for different reasons related to the venturi effect that is caused by the air leaving the regulator. What happens is the lowering of pressure in the second stage case and effect keeps the diaphragm depressed. You will find nearly any well tuned regulator will do this.

    Restricting the flow, by either turning the reg mouthpiece down in the water or placing your thumb over the mouthpiece will slow the flow, increase the pressure in the case and cause the diaphragm to return to the normal position and stop the air flow.

    If you are having a problem at depth with your octo doing this, then you can perhaps use one of the clips that most dive shops have that have a mouthpiece insert or cover that are designed so that the octo can be pulled away from the clip when needed, however by covering the mouthpiece in the stowed position, prevents freeflowing.
     
  7. Fishpie

    Fishpie Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Fort Lauderdale
    1,686
    249
    63
    Turn your venturi to minus, screw in the cracking pressure knob a turn or two, don't use a "scum ball" holder, keep the mouthpiece pointing down when you jump in.
     
  8. redacted

    redacted Guest

    Once your octo fills with water, that problem will not occur. A scum ball make it harder for the octo to fill with water. Lose the scum ball, enter the water with the oct mouthpiece pointed downwards, and slowly turn the mouthpiece upward to fill the octo with water.
     
  9. tfsails

    tfsails Divemaster

    # of Dives: 200 - 499
    Location: Richmond VA
    640
    4
    0
    Any second stage will free flow if it has no water inside it and it is turned so that the diaphragm is pointed down. That's a good thing! It's what it's designed to do. You can prove this to yourself by pointing it mouthpiece up on the surface and dipping the reg slowly below the surface, with the mouthpiece still pointing up. It will start to free flow as you dip it deeper. The pressure differential between the water under the diaphragm and the surface depresses the diaphragm, pushes on the demand lever and air flows.

    If you fill the second stage up with water, you can turn it any direction you want and it won't (shouldn't, anyway) free flow. There's no pressure differential, so the diaphragm doesn't collapse, the demand lever isn't pushed, and no air flows.

    All of the above is assuming that the reg does not free flow out of the water. If that happens, it needs to be re-tuned by a technician.

    The way to stop the unused reg from free flowing is to allow it to fill up with water. Once it does, it'll stop.
     
  10. herman

    herman Divemaster

    # of Dives: 500 - 999
    Location: Raleigh,North Carolina
    9,488
    2,050
    113
    Just to define freeflow a little, if the reg has a venturi assist, and most do and it's set to something more than mimimum, a properly tuned reg will freeflow out of water once flow has been established by pushing the purge button. It will continue to do so until backpressure is somehow established. It should not start on it's own or slowly leak air but with a venturi assist set above minimum and the purge button pressed, a full freeflow is normal.....if it doen't, it's time to see your reg tech.
     

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