How to properly use dive/predive lever and adjustment knob?

[Lorenzoid]

your assumption is incorrect, the knob and the lever have different functions, the knob determines how easy it is to start the air flowing and the lever how easy it is to maintain the air flowing. when set to minimum they minimize freeflowing.

Great explanation. Thanks. I've been reading about regulator design, and I do understand.

 

[BoltSnap]

Here is what I do/don't do:

When getting ready to dive I set both my primary and alternate to venturi lever in the - position and the adjustment knob all way. Once I am in the water and the primary is in my mouth, I turn the adjustment know all the way out (unless it leaks, then I turn it back just to stop the leak. I'll have it serviced later since no leaks should be there with knob all way out) and the venturi in the +. The alternate SS remain in the -/knob all way in throughout the dive. Once I am on surface and the primary isn't in my mouth anymore, all adjustments go back to - and way in.

Once on the boat and done with diving, I put all adjustments in the out/+ position(s) to reduce pressure on internal springs. All adjustments are in the +/way out for storage.

Note:

1. Atomic Regulators (this is what I am using now): you can only adjust the cracking pressure with the knob that goes in for high cracking/more difficult to open and out for less cracking/easier to open. The venturi adjustment is automatic in the Atomic and is actually dependent on the depth and hence no venturi active on the surface. VERY nice way of doing it by Atomic regulators.

2. Aqua Lung: The high end AL regulators have one adjustment knob that actually controls both the venturi and cracking pressure. Neat feature IMO.

 

[beanojones]

OP here. Thanks for the replies so far. Question: It sounds like both the adjustment knob AND the venturi lever are intended to be used to minimize freeflows. Then why the need for BOTH of these features? I mean, why not just have a knob OR just have a lever?

Here's a way to see how they work differently, maybe:

With the reg out of your mouth, and the lever to +, a push on the purge button should result in a free flow that won't stop until their is some back pressure (a single finger 'shushing' the reg should do). That + or - allows a vane inside the reg to either create flow that continues to give until back pressure is applied, or to make the flow stop when suction stops.

The winding knob increases tension on the spring, which make the 'cracking effort' higher or lower. Why would one ever want a reg to be 'harder' to breathe? Well when one is facing into a current there might be times when one wants the cracking pressure to be higher so as to stop the surging that the flow of water can cause. Plus for fine control when spending a good deal of time head down.

 

[Lorenzoid]

Here's a way to see how they work differently, maybe:

With the reg out of your mouth, and the lever to +, a push on the purge button should result in a free flow that won't stop until their is some back pressure (a single finger 'shushing' the reg should do). That + or - allows a vane inside the reg to either create flow that continues to give until back pressure is applied, or to make the flow stop when suction stops.

The winding knob increases tension on the spring, which make the 'cracking effort' higher or lower. Why would one ever want a reg to be 'harder' to breathe? Well when one is facing into a current there might be times when one wants the cracking pressure to be higher so as to stop the surging that the flow of water can cause. Plus for fine control when spending a good deal of time head down.

Just to clarify the latter remarks for someone who needs it spelled out for him, exactly what might I experience when facing into a current? Do you mean I might experience free-flow? And if so, I would turn the knob inwardly, so as to increase cracking pressure?

What about the head-down position you refer to? Are regs more prone to free-flows when I'm in a head-down/feet-up position?

 

[beanojones]

It won't be a full on free-flow, it just might be a little extra flow, in either case. In both case, either because of the current helping push the purge button a bit, or because head down adds a little bit of pressure difference from the slightly greater depth in the water column from where the first stage is, turning the know in counteracts that extra push.

Most people do not have their regs set-up to be so light breathing, prefering to not have to futz with the knob underwater.

But I always setup my personal regs to be this light breathing, so I am used to playing with the knobs.