Mild Freeflow While Inverted

[2airishuman]

I was experimenting with a new configuration yesterday and had a trim problem that caused floaty feet. I'll take care of this for future dives and am not seeking advice for this aspect of the problem.

However I noticed that while partially inverted my regulators had a tendency towards a mild freeflow while I was inverted. Typically it would occur at the end of exhalation, and would stop when I took my next breath. My second stages are metal Aqua-lung regulators, and I ran into this both on the one with the older and the newer style exhaust Ts.

Should I try to adjust the regulators to prevent this, or is it just something I should be prepared to deal with when upside down?

 

[Reku]

You could keep the venturi switch and the adjustment knob shut when you are not using them and then also when you invert turn the venturi switch half way. Honestly this isn't too much of a problem you could also just be aware that it could happen and then deal with it accordingly. Are you going to be spending much time inverted?

 

[CptTightPants21]

What exact model of Reg?

Free flowing while it was in your mouth or when it was out of your mouth?

Would follow Reku suggestion with the venturi switch and adjustment knob to see if that fixes the issue, otherwise you may need it to get it slightly adjusted--should take a dive shop less than 5 min and be no charge.

 

[MXGratefulDiver]

It's fairly normal with a lot of regs ... particularly some of the higher performance ones. My ScubaPro regs don't do it, but most of the Apeks regs I've owned over the years did ...

... Bob (Grateful Diver)

 

[tbone1004]

what they said, it isn't abnormal. Make sure your secondary has the venturi off and adjustment turned all the way down. On your primary if you are going inverted just flip the venturi lever and it shouldn't freeflow. It's not uncommon on the higher performance second stages, particularly if they have been tuned very light

 

[2airishuman]

You could keep the venturi switch and the adjustment knob shut when you are not using them and then also when you invert turn the venturi switch half way. Honestly this isn't too much of a problem you could also just be aware that it could happen and then deal with it accordingly. Are you going to be spending much time inverted?

These regs don't have a venturi switch or adjustment knob.

I don't plan to spend much time inverted and can certainly deal with this if it's something to be expected. I just want to be sure I have my regs set up correctly, and it sounds like I do.

What exact model of Reg?

The second stages are metal US Divers Aqualung regulators from the mid-1970s that were originally sold as part of Conshelf XIV, Conshelf XII, or Calypso IV regulator sets.

I was trying out two first stages, a HOG D1, and Conshelf XIV that I recently rebuilt.

Free flowing while it was in your mouth or when it was out of your mouth?

It was in my mouth.

Would follow Reku suggestion with the venturi switch and adjustment knob to see if that fixes the issue, otherwise you may need it to get it slightly adjusted--should take a dive shop less than 5 min and be no charge.

No venturi switch or external adjustment knob. I work on my own regs, and can turn them down a touch if I really have to, but I like the way they breathe now. I guess you've made the tradeoff clear.

It's fairly normal with a lot of regs ... particularly some of the higher performance ones. My ScubaPro regs don't do it, but most of the Apeks regs I've owned over the years did ...

Thanks; it helps to know that it's a common condition. I'm paying close attention to the way the regs work since I just serviced them. Many people wouldn't have noticed.

what they said, it isn't abnormal. Make sure your secondary has the venturi off and adjustment turned all the way down. On your primary if you are going inverted just flip the venturi lever and it shouldn't freeflow. It's not uncommon on the higher performance second stages, particularly if they have been tuned very light

Thanks. Again they don't have any external controls, and I do have them tuned pretty light. I settled on these regs because of their durability and their resistance to icing up in cold water, both products of the metal body. I've been buying them on ebay and cleaning them up and going through the service procedure with them.

 

[John C. Ratliff]

Okay, I think most of the posters have missed this situation. This is a normal situation for all modern second stage regulators built in the standard configuration where the exhaust valve is separated from the diaphragm. Most of these regulators now have an inhalation resistance which is about 1/2 inch of water pressure, cracking effort. If you are in an inverted position, the exhaust valve is almost an inch above the diaphragm, and so it will leak air simply due to the water pressure's having over one-half inch of "head" on the exhaust valve. This is normal for these high-performance regulators, especially if they have a larger, separated exhaust valve. It is something that can be safely ignored as due simply to physics and the design of the second stage. It will stop as soon as you are in a position where the exhaust is at the same level, or lower than, the center of the diaphragm.

SeaRat