Hose and fitting changes to 2nd stage

[ScubaSteveT]

I recently changed out the Atomic comfort swivel hose on my B2 to a 40” DGX braided hose and 70 degree Dive Rite “high flow” fitting with the jam nut. Trying this setup for the first time this past weekend, I certainly enjoyed the comfort and less bulk of the loop. I also noticed that any time I would purge above water the 2nd stage will free flow and I can stop it by snuffing the mouthpiece. I did not try purging underwater. This was not how the regulator performed prior to the hose and fitting changes. I assume it’s just tuned right on the edge and this setup flows a little more to keep the Venturi effect stuck? It works fine and I’m planning to keep using it, I was just interested in how this changes.

 

[lexvil]

Turn the adjustment knob in 1/4 turn and try it, repeat until it doesn’t freeflow.

 

[ScubaSteveT]

I did try turning the adjustment knob all the way in and I would say that it wasn’t as quick to free flow but still did. I’m just surprised a hose and fitting would make this much of a change.

 

[James79]

Many modern second stages can be tuned light enough that a strong purge will cross over into freeflow. As long as covering the mouthpiece stops it, that's perfectly fine. If I recall correctly, some manufacturers actually expect that behavior and check for it during maintenance.
Respectfully,

James

 

[lexvil]

I did try turning the adjustment knob all the way in and I would say that it wasn’t as quick to free flow but still did. I’m just surprised a hose and fitting would make this much of a change.

How does it breath compared to before the hose change?

if turning the knob all the way in has that small of an effect it may need a retune, have you checked the IP?

 

[ScubaSteveT]

I thought it was breathing normal, it’s always been great and still was. I don’t have an IP gage, but the only thing I changed was the hose and fitting.

It seems like there might be slightly higher flow increasing the Venturi effect? This reg has the AFC feature, so there is no easy way to dial the Venturi back.

 

[Nemrod]

If a second stage with the Venturi in dive mode will not free flow then something is wrong. That in fact is a check for the Scubapro regs in the manuals, if the regulator will NOT free flow it needs additional adjustment.

An Atomic, since it has the automatic Venturi control, probably should not free flow generally, but I have never set up an Atomic second stage. Maybe enquire of some of the Atomic experts down in the Regulator Forum.

I doubt the hose would be the difference, stranger things have happened though, but I doublt it.

 

[lexvil]

As above I doubt the hose is responsible but…
my guess is something else got moved with the nut installation but without having it in hand it hard to say. You should get an IP gauge to keep track of the first stage health and to rule out IP creep as a cause.

 

[lowwall]

It's theoretically possibly your new hose and hardware setup might be slightly less constricting resulting in a slightly higher IP at the second stage.

You wouldn't be able to check this with an IP gauge because it gets attached to the low pressure inflator hose. Even if you rigged one up to the hose that your second stage is on, the gauge isn't precise enough to make such a difference discernible. Well maybe the $150+ pro ones are, but not the $15 gauges that most of us use.

But an IP gauge is still worth having because it's a cheap and easy way to check the general health of your first stage. See step 10 of the late and great Couv's Regulator Inspection and Checklist post:

Regulator Inspection and Checklist (Rev-8)

Discussion of this thread can be found here: http://www.scubaboard.com/forums/regulators/260452-regulator-checklist-inspection.html First off, I would like to acknowledge my friends who have done more than their share in developing this checklist. Due to my laziness and resistance to answering...

scubaboard.com

 

[ScubaSteveT]

Very helpful, thanks!