Question about freeflowing when handing off primary reg

[tfsails]

Everybody's advice here seems accurate. Zeagle's repair manual mentions the free flow with the lever in the "+" position and how it should stop about 2/3 the way to "-" .

By definition, ANY regulator you take out of your mouth on a dive has no water in it; think about it--you couldn't breathe off it if it had any water in it. Ergo, when you remove the reg and point it mouthpiece up it's gonna freeflow. It will continue to free flow unless you manage to fill it with water. At that point, it will stop freeflowing. Just turning the reg over should stop it, but the vacuum inside the reg from the flowing air may be sufficient to keep it freeflowing (remember Bernoulli and his principle?). If it continues to freeflow after it's full of water, it's maladjusted.

Ahh, the physics of diving!!

 

[herman]

Everybody is right that turning the mouthpiece down should prevent this. But if the reg isn't freeflowing into your mouth, and you keep the mouthpiece in the same orientation it was in when it was in your mouth, it shouldn't freeflow. So I'm going to talk about the procedure for donating.

You reach up and grip the hose close to where it joins the primary second stage, with your palm facing toward you. You then pull straight away from you and rotate your wrist so that your palm is now facing your buddy. You have to duck your head when you do this, so that the long hose will slide over it. The mouthpiece should remain oriented horizontally during this procedure, so it shouldn't freeflow.

If it's tuned well (or maybe I should say tuned for min breathing resistance) and the venturi assist set to full it will likely freeflow if you do not do something to prevent it, like turning it down. As you move the reg away from your mouth you are causing 2 effects that will make the reg start to flow air. There will be a slight vaccum formed at the mouthpiece by the water passing it (you are moving it toward the OOA diver) and at the same time pressure will be placed on the diaphram, pressing it in. It's not a lot of pressure but the 2 forces add and once the reg starts to flow the venturi assist will continue the process until the reg is in full freeflow or something is done to prevent it. Granted, a lot of regs will not start to freeflow simply because a lot of techs are not willing to tune them to that level, my personal ones will.

 

[tfsails]

Tuning a second stage is always a balancing act between being right on the edge of free-flowing and making the reg so tight it feels like you're sucking a golf ball through a garden hose. I tend to tune on the easy side because I like easy-breathing regs, but I put my customers at some risk of a slight free-flow after a dive or two.

With some brands you're striking a balance between free-flowing, easy breathing, and the ability to purge the reg. Some brands want you to have a rattle when you shake the pressurized second stage from the demand lever hitting the backside of the diaphragm. Other brands specify no rattle.

Tuning second stages is a combination of physics and black art. All of this is what makes servicing regs so much fun and it can be a challenge! Believe it or not, in my experience the easiest second stage to tune is the old Poseidon Cyklon. Piece of cake!