Scubapro MK2/R390 octopus free-flows on first water entry then stops.....?

jo8243 · Jun 7, 2006

I had my scubapro MK2/R390 reg serviced several months ago, and afterwards I've noticed that when I first enter the water, my octopus will free-flow when it is turned with the mouthpiece facing upwards. If I rotate it so the mouthpiece is facing down, it stops. Then, after 30 seconds or so, I can turn it back mouthpiece up and it won't free-flow. It is set to pre-dive on the adjustment knob, so that's not it.

Is there anything I can adjust to stop this or do I have to send it back to the shop? I'm mechanically inclined and I'm not scared to mess with it a little if someone can give me some tips. I will send it back if I have to but it's a PITA since there is no scubapro shop nearby and I have to UPS it.

Anyone?

Thanks

PerroneFord · Jun 7, 2006

My regs all do this. I never saw it as a problem. Let's me know the gas is on! Intermmediate pressure might be a little high if it's freeflowing on pre-dive.

DA Aquamaster · Jun 7, 2006

When you first enter the water the second stage (octo) is full of air, the air leaks out the up turned mouthpiece and the combination of less air inside and more water pressure outside presses the diaphragm inwards causing the valve to open and a freeflow to start. Once the second stage floods, this will not occur as the pressure is the same inside and outside the second stage.

If the mouthpiece is turned downward on entry, the air rises farther inside the octo while water enters through the mouthpiece to equalize the pressure and no freeflow will result.

As for adjustment to prevent the problem (other than by ensuring the mouthpiece is not facing up) the R190 and R390 have a flow vane adjustment. Make sure this is turned to "Min" to minimize any tendency to freeflow.

redacted · Jun 7, 2006

jo8243:
It is set to pre-dive on the adjustment knob, so that's not it.

That adjustment does not prevent freeflows, but it will make them less severe. Your reg is doing exactly what it should.

jo8243 · Jun 9, 2006

DA Aquamaster:
When you first enter the water the second stage (octo) is full of air, the air leaks out the up turned mouthpiece and the combination of less air inside and more water pressure outside presses the diaphragm inwards causing the valve to open and a freeflow to start. Once the second stage floods, this will not occur as the pressure is the same inside and outside the second stage.

If the mouthpiece is turned downward on entry, the air rises farther inside the octo while water enters through the mouthpiece to equalize the pressure and no freeflow will result.

As for adjustment to prevent the problem (other than by ensuring the mouthpiece is not facing up) the R190 and R390 have a flow vane adjustment. Make sure this is turned to "Min" to minimize any tendency to freeflow.

Ok, this makes sense. But why did it never do that before I had it serviced? Was it set too tight from the factory or something?

chrispete · Jun 9, 2006

The reg tech probably did a good job on tuning them.

Your octo probably had a tighter setting from the factory which required more diaphram pressure to 'crack' the valve open, the reg tech probably tuned it with lighter pressure, so it takes less pressure difference on the diaphram to open the valve.

DA Aquamaster · Jun 10, 2006

The inhalation specs for an octo are normally about 1 inch of H2O higher than for the same model when used as a primary. There are pros and cons to this. It is more freeflow resistant, but it breathes like a rock - not a great thing when you need it.

yankeestudent · Jul 5, 2011

Scubapro has a fix for any octo free flow on entry,it is an octo clip with a plug that goes into the mouthpiece,regardless of entry position no freeflow .
Talk to your scubapro dealer.

Zung · Jul 6, 2011

If you're mechanically inclined, AND if you have the tool (or the tricks) to deal with the splined hose nut, here's a quick fix: remove the hose; inside the hole, there's a slotted plug called orifice. Hold down the purge with one hand, and, with an appropriate screw driver, turn the orifice clockwise by 30°, or from the 12 o'clock position to the 1 o'clock position. That should quiet it down by making it a bit harder to breathe.

The gurus would tell you you should also re-adjust the lever height. While this is formally correct, I'd say it's not required for a 30° tweak.

halocline · Jul 6, 2011

Since it's been almost exactly 5 yrs, I suspect the guy's tank has emptied and the reg has stopped freeflowing....

Scubapro MK2/R390 octopus free-flows on first water entry then stops.....?

Please register or login

jo8243

Contributor

PerroneFord

Contributor

DA Aquamaster

Directional Toast

redacted

Guest

jo8243

Contributor

chrispete

Contributor

DA Aquamaster

Directional Toast

yankeestudent

Registered

Zung

Contributor

halocline

Contributor

Similar threads