Regulator Adjustment

[coldincanada]

I was out at the lake during the summer. Discussion got around to regs. I was told that some regulators are easier to breath from then others. Some are hard to breath from and others easy to breath from if you all understand what i am gettign at.
What is the difference and how does one adjust and or figure out what one has a preference for????

Lost deep deep down

[Ron G.]

My question may be related to the OP's?

On most (all?) regulators, there's a dial or knob for adjustment. What does that do? I thought it might do exactly what OP was asking....adjust the amount of airflow.

Ron

[dannybot]

On the second stage of an adjustable reg, there will be a knob, usually opposite the hose. Turn it one way to make it easier to breathe, then the other way to give more restance. You can set some at the surface and the resistance will stay the same throughout the dive, but others require fine tuning as you get deeper to breathe easy, then detuning as you ascend to prevent freeflow.

Some regs also have a second knob or switch to prevent freeflows at the surface. Generally speaking, the more expensive a reg, the more toys.

There is also a balanced first stage, which automatically adjusts the first stage with the ambient pressure as you ascend or descend. So you would, in theory need less fiddling with the adjustment on the second stage.

If you look around, I'm sure you can find better explanations of features to look for in a reg: balanced/unbalanced first stage, environmentally sealed, DVT, adjustable second stage, swivels, predive switch..., and how they all work.

Unfortunately, the owners' manuals I have received do not explain all of this very well.

[ReefHound]

User adjustable second stages are not universal though they seem to be getting more common. They used to be found on high end models now are showing up on intermediate models. They are great and can allow you to stop a nagging free flow on the surface or swimming into current, and can open it up when you need for air. But they are a fine tuning adjustment and depend on the internals being adjusted within spec so it does not replace annual service and maintenance.

[in_cavediver]

For a really good explanation - get one of the reg books from Peterbuilt or Airspeed press.

The following explanation is for a Dive Rite second as I just rebuilt one.

First, understand the valve itself is made up of a plastic/polymer seat (hollow) and 'knife' edge valve body. The valve body is on threads and moves in and out. The seat is on a spring with lever to connect the purge. The back of seat assembly ties into the adjuster knob which is threaded as well. The tube where the spring/purge lever mount has a hole in it where the air is expelled.

ASCII pictorial:
Hose --->Tube--->knob
Hose --->Knife edge->Seat assembly->Spring-Airhole->knob

The lever for the purge button mounts on the tube and ties into the seat assembly to manually move the seat away from the knife edge.

During operation, a balance of pressures is achieved where the air space in the reg plus the spring pressure = the intermediate pressure of the reg. When you inhale, you drop the ambient pressure and the pressure in the hose forces the knife edge away from the seat, thus allowing air flow. Once the pressure equalizes, the seat closes stopping air flow.

Given that description, there are two way to increase/decrease the spring pressure holding the 'knife' edge on the seat. The primary one is the knife edge itself. Its on the hose side and is adjusted with an allen key. The other way is using the knob on the side of the reg to move the back seating surface of the spring (adjusts its compression). As the seat wears, you can use the knob to increase the seal pressure to prevent seepage and free flows. It will also increase inhalation effort as well. This is why its not a substitute for replacing the LP seat.

[Wetnurse28]

When I bought my Atomic M1 they guy said not to fiddle with it and leave it in the most open position.

I understand the freeflow concept. Why not just leave the knob all the way open. I personally have not had any issues.

It seems to me that when you want air, you dont want to have to breath harder to get it. I never truely understood the knob.

Am I missing a key point?

[Grin]

Yes. The reg is much more likely to freeflow out of the water when set to breath super easy for depth. So, kind of basically, your reg is only as much of a easy breather at depth, as you are willing to deal with freeflowing out of the water. Some regs have some sort of (predive etc...)adjustment where you can set it to not freeflow up top but, when in the water, you can adust it to super easy gas delivery mode. And it really does make a big difference. The deeper you go the bigger the difference is. If your in the predive mode and go down to 100 ft, then throw it in dive mode, you will instantly feel the delivery of gas become so much easier. What happens is newbys focus on free flowing and think they have a crap reg, so the shop tightens up the reg and the newby is happy. They are not smart enough to realize they now have to drag much harder on that reg at depth. So in actuality a properly set reg should be set so it can be made to freeflow out of the water, if you try to make it freeflow. But not so much that it freeflows uncontrollably. If you cannot get it to freeflow out of the water, at all, it is set to tight. If your reg has predive knobs or levers or both, you should 100% be able to get it to freeflow by setting it to dive mode out of the water, and simply hitting the purge button. Then put it in predive mode and it should either be impossible to get to freeflow, or at least it should make it not freeflow easily out of the water.
Most regs are adjusted in the 2nd stage with a allen wrench. But you should be careful and know a little before messing with this. It's not rocket science, but basic understanding is a good idea.
Typically you would adjust the allen a hair, and put the 2nd stage back on the hose and test it, for what point it freeflows at, then re-adjust the allen adjustment over and over, until you get it correct to your personal idea of whats correct.
Some are afraid of freeflow, but when you realize that is what gives you great easy gas delivery at depth, you start to appreciate a reg that is set correct and will freeflow, a hair, on the surface. Of course backup 2nd stages would be set a hair tighter so they don't ever freeflow. They are going to be harder to drag a breath out of, but they are for emergencies, not comfortable breathing. You don't want freeflowing issues with your backup 2nd stage.
The cheapest regs can be made to breath very good by setting them right.

[Navy OnStar]

Originally Posted by Wetnurse28

When I bought my Atomic M1 they guy said not to fiddle with it and leave it in the most open position.

I understand the freeflow concept. Why not just leave the knob all the way open. I personally have not had any issues.

It seems to me that when you want air, you dont want to have to breath harder to get it. I never truely understood the knob.

Am I missing a key point?

I have 2 knobs on my ScubaPro MK25/S600. 1 is a flow adjustment knob and the other is a predive/dive knob. The predive/dive knob turns a little bar, just behind the mouthpiece. This bar is flat and in predive it is blocking some of the opening to prevent freeflow. In Dive it is not blocking the opening and allows for easy breathing. This is the rough adjustment. You should really have this knob in Predive on the surface and Dive whenever you are underwater regardless of depth. The second knob is the fine tune adjustment that actually sets the inhalation effort of the reg around the point that whoever serviced your reg last has set it internally.

For example: (these numbers are for illustration purposes only and have no actual meaning.) Say your tech sets your reg to a breakthrough pressure (ease of inhalation)of 1psi. The knob on the side would have like a +/-.2psi range of adjustment around that 1psi.

If I set my flow to the easiest breathing setting on the surface. It will still freeflow in predive if facing up. I usually have it somewhere in the middle so it won't freeflow on the surface and usally won't touch it unless I go deep. I always put the reg in predive on the surface and dive once it goes in my mouth to descend. At less than 60ft I really can't tell the difference in inhalation effort for the whole range of adjustment. Below 60ft I can start to feel the difference.

[5513]

Originally Posted by Wetnurse28

When I bought my Atomic M1 they guy said not to fiddle with it and leave it in the most open position.

I understand the freeflow concept. Why not just leave the knob all the way open. I personally have not had any issues.

It seems to me that when you want air, you dont want to have to breath harder to get it. I never truely understood the knob.

Am I missing a key point?

I did pretty much the same thing with my new Aeris Pro. But I got head into a current on a drift dive and had some free flow. I ended up with a much shorter dive because of the air loss. When I got home I spent some time with my dealer and he tuned me up on the finer points so I can properly adjust the second stage to avoid in current free flows.