confused!!!

scubaboy10 · Nov 11, 2009

ive been looking into getting my own gear and heard about 2nd stage adjustable regulators. if i understand correctly as you descend you need to adjust it and as you ascend you need to adjust it as well. It sound kind of un needed? also whats the difference between the adjustment knob and the venturi lever? do you need both of them?

thanks

keithdiver · Nov 11, 2009

makes it a lot easier!!!

Mr Carcharodon · Nov 11, 2009

The adjustment knob adjusts the pressure on the second stage piston and typically you adjust it on your first dive and forget about it for a long time. The adjustment consists of turning the knob until the regulator just starts to freeflow and then turning it back a bit. Over the course of months you may need to do tweaks but this is not something you do continuously on a given dive.

I have found the verturis to be fairly useless in the water. As with many things in scuba gear its primary use may be to sell you something in a store.

highdesert · Nov 11, 2009

For me, set it and forget it is closer to the reality of second stage tweakers ... YMMV.

scubadobadoo · Nov 11, 2009

Yep, set it and forget it for the most part. It is nice to be able to do a quick adjustment say on vacation or right before a dive when tuning it back will stop a small free flow and allow you to keep diving. It's one of those things you rarely need to have UNTIL you need it.

snowflake4727 · Nov 11, 2009

The adjustment knob makes it easier or harder to breath from. Sometimes when facing a current or scootering one may need to de-tune (make it harder to breathe from) to keep it from free flowing. Most people set it at the easiest setting and forgetting it.

The venturi adjustment (also called a dive/pre-dive switch) is used to stop it from free flowing before or after a dive but genrally not during a dive. When beginning the dive the diver loosens this up so it is easier to breathe.

Usually the venturi has a very short adjustment range and often times just a switch.
The adjustment knob generally has a longer adjustment range.

scubaboy10 · Nov 12, 2009

what depth do you set the 2nd stage? while your floating?

walke121 · Nov 12, 2009

I don't ever mess with it. I played with it alittle bit when I first started diving but now they are just all opened all the way and thats how I dive them. Only turn them back when current causes them to free flow.

tfsails · Nov 12, 2009

The venturi lever smooths out the air flow inside the second stage and uses Bernoulli's Principle to make the effort of breathing easier. Or harder. A secondary feature is that it will usually stop a runaway free-flow on the surface if you put it in the "-" or "pre-dive" position. It does this by creating turbulence in the air coming into the second stage and not creating an area of low pressure on the inside of the diaphragm. Bernoulli assures us that the area of low pressure will be there when the venturi is in the "dive" or "+" position, and that makes the effort of breathing a lot lower.

BTW, Mr Carcharodon, there is no piston in a second stage, only a poppet and a demand lever. The knob on an adjustable second stage varies the spring pressure against the back of the poppet which keeps it closed when not inhaling. More pressure = harder breathing effort (cracking pressure).

scubaboy10 · Nov 12, 2009

is free flowing a big problem? i thought a regulator is designed for air ON DEMAND? not not on demand! ive heard alot of stories of free flowing regs on the surface but also underwater with a 1st stage malfunction is it likely it will happen?

confused!!!

Please register or login

scubaboy10

Registered

keithdiver

Contributor

Mr Carcharodon

Contributor

highdesert

ScubaBoard Supporter

scubadobadoo

Contributor

snowflake4727

Contributor

scubaboy10

Registered

walke121

Contributor

tfsails

Contributor

scubaboy10

Registered

Similar threads