Regulators with Flow Adjustable Knobs

[Vegan Shark]

What's everyone's experiences with regulators that allow you to adjust the flow of air with a knob mid-dive? I've just started diving Hollis D212s, and it's a very new experience compared to normal regulators. I like the idea, but not sure what the possible drawbacks are...although for switching regs I am finding it tricky at first; when not in use I have my backup set on the lowest setting to prevent freeflow, which means I barely get any air when I switch to it at first. Then I would accidentally set it too high when in use, and during a switch it would violently freeflow if I forgot to adjust it back down before removing from my mouth.

Ideas on these regs?

 

[Linedog]

My second is adjustable, I find myself cranking it a bit open after 70 feet or so, just a bit not much at all really. If I forget to twist it closed as I come up it will dribble/bubble a bit. If I totally forget it will free flow as I exit.

 

[tbone1004]

linedog, you need to get them serviced properly, the tech tuned them too hot.

Disclaimer, I dive Poseidon Jetstreams, so don't have them, don't need them. On the Apeks/Scubapro style second stages, the knob is primarily to prevent freeflow. They should be tuned all the way out when they are in use, and they should be at their specific cracking pressure with the knob all the way out. On your secondary second stage, and on your primary if you are diving into current, descending quickly, or whatever may be going on, you want to detune it all the way so it is less liable to freeflow. Should never be halfway, either on or off. The venturi lever also helps with this, but they should be used together.

 

[tech3324]

I have a HOG Classic 2nd stage with both dive/predive lever and inhalation adjustment knob. The dive/predive lever is useful to prevent free flows and I use it regularly, but the adjustment knob isn't of any real value to me. Breathing effort is about the same at both extremes, so I set it to the middle and forget it.

 

[tbone1004]

if you don't notice a change, they aren't tuned right to begin with. Some second stage manuals recommend a slight freeflow when all the way open, others now. It is a balance that has to be made with the first stage it is connected to though, can't do it properly without having the matching first stage otherwise the IP change is actually enough to cause the second stages to have differing cracking pressures, lower with higher IP and vice versa

 

[Vegan Shark]

If you experience a random free-flow during a dive (cold whatever, malfunction, whatever) would switching it to pre-dive and de-tuning it all the way help matters compared to a regular un-adjustable 2nd stage?

 

[Got2Go]

I use a HOG and tune it so it creeps slightly at the knobs least restrictive setting.
While diving, I will adjust it so that it is the least restrictive without creep.

When getting gear ready for a dive, I will keep it in the most restrictive setting to prevent free flow, and adjust as needed once in water.

And, when the reg is packed, I store it with the knob in the least restrictive position to help minimize LP seat imprint.

 

[tstormdiver]

linedog, you need to get them serviced properly, the tech tuned them too hot.

Actually, properly tuned,... Ocenaic/ Hollis/ Aeries adjustable second stages should have a very slight "leak" when the knob is turned all the way out. A 1/2 turn in or so should stop this "leak". If not, then, it may need adjusting. At least that is what I was taught at the Oceanic/ Hollis/ Aeries regulator seminar I went to a DEMA last year. What linedog stated sounds like his 2nd stage is properly tuned.

 

[halocline]

although for switching regs I am finding it tricky at first; when not in use I have my backup set on the lowest setting to prevent freeflow, which means I barely get any air when I switch to it at first. Then I would accidentally set it too high when in use, and during a switch it would violently freeflow if I forgot to adjust it back down before removing from my mouth.

"Barely get any air" is likely an exaggeration, right? 'somewhat more difficult to breathe' might be a more accurate description of how it should feel, and the reg should still deliver plenty of air with the adjustment knob turned all the way in. Although I'm not too familiar with hollis gear, I seriously doubt any manufacturer would design a regulator so that the adjustment knob would actually restrict the air flow to the point where you can't breathe. It's a pretty subjective feeling when you switch regulators, and it's easy to feel like you're not getting enough air. If you really can't get air with the adjustment knob all the way in, it's definitely not adjusted correctly.

It sounds like the reg has a lot of venturi assist, which would explain the 'violently freelowing' when you take it out of your mouth. Any well tuned high performance 2nd stage will flow air if you remove it from your mouth and don't turn the mouthpiece down. Once it starts, if there's a lot of venturi assist, that will really get it going fast, and that sounds like what you're describing. You might try turning the venturi assist off (or to minimum) if there's a separate lever or knob for that. That should not increase the cracking effort at all but should at least slow down the free flows.

Most modern 2nd stages have a lot (too much IMO) venturi assist, because the manufacturers have determined that small 2nd stages (more linear flow, less internal volume, = more venturi assist) and lower WOB numbers on the testing machine (venturi certainly helps achieve that) help move regulators off the dive shop shelves.

I like adjustable 2nd stages but the adjustable ones I use do not have venturi assist adjustment, so it's helpful with keeping my secondary from flowing when I enter the water.

 

[fbk]

I use a HOG and tune it so it creeps slightly at the knobs least restrictive setting.
While diving, I will adjust it so that it is the least restrictive without creep.

When getting gear ready for a dive, I will keep it in the most restrictive setting to prevent free flow, and adjust as needed once in water.

And, when the reg is packed, I store it with the knob in the least restrictive position to help minimize LP seat imprint.

saved me typing