View Full Version : Oceanic DeltaIV - basic questions on the features of it

10-08-2007, 02:37
Hi guys,

I have recently purcahsed my first set of regs which consists of a Oceanic Delta IV second stage. Among some of the features is a switch up the top which I was told briefly that would stop freeflowing (i think).
I noticed that when I hopped in the water, with the switch closed, it still freeflowed. It did freeflow less than when it was open, but it still seemed to be quite alot of air.
I was just wondering if I have gotten the purpose of the switch wrong or is that how it is meant to work (stop freeflowing a bit, but not completely).

ScubaToys Larry
10-08-2007, 08:31
A regulator by design will let air out (free flow) if there is more pressure on the outside of the diaphragm, than the inside. That is how they work. You inhale, it gives you air. So since that is how they are made, if you get in the water, and have air in the second stage, and hold the mouthpiece up, diaphragm down - there is more pressure on the outside of the diaphragm - and it will give air. Physics.

Now if you are standing on land, and nail the purge button, you will see that it starts free flowing - and stays that way, even if you release the purge, if your lever is in the "+" or "dive position". They are using a venturi effect so that as the air starts flowing, it causes a venturi effect inside the reg that keeps the diaphragm sucked in as the air flows. If you simply put some back pressure on it by putting your thumb in the mouthpiece hole - it stops.

That switch does about the same as putting your thumb over the hole - except internally.

So it limits the flow - but it is not an on-off switch for the reg. Just make sure it's in the "-" position, and when you jump in, make sure you point the mouthpiece down if you take it out of your mouth (or it's an octo) then tilt slowly and let it slowly fill with water. Once water is in it, the pressure on both sides of the diaphragm are balanced and it will not free flow.

Hope that makes sense?!:smiley5:

10-10-2007, 03:47
Larry, thanks heaps for the advice. I am starting to get my head around it now.

So to sum up (please correct me if I am wrong).

a. When I jump in the water, have it switched to '-' and place it mouthpiece down. Once it has pressurized, I can then have it floating whichever way I want and it wont freeflow unless i switch it to '+' or it reaches the surface again and it bobs back in the water mouthpiece pointing up.

b. While I'm in the water and ready to dive, I switch it to '+' which will then let the 'venturi' feature work, allowing me to breathe easier as my depth changes.

So all in all, it functions as a normal regulator, but limits the freeflowing to an extent internally, but cannot limit freeflowing completely as it must still allow air through if the pressure is great enough (so that we can breathe out of it regardless of the switch position)

ScubaToys Larry
10-10-2007, 07:16
Bingo... you pretty much got it. One other thing I'd point out, is you can run into the free flow not only at the surface, but under certain conditions at depth. For example, if the reg is in your mouth, and you inhale and get it flowing, then take it out of your mouth with the mouthpiece up - again, you'll get the free flow. It's also possible if you grab it and move it through the water quickly, leading with the diaphragm, that could make it do the same thing.

But it sounds like you've got it down!

10-10-2007, 10:56
Legend! :smiley20:
Thanks for your help Larry... now... time to order those torches hehehe