Can I swap a second stage between two different 1st stages?

[raviepoo]

I have an Aqualung Cousteau Micra Adj reg with a DIN fitting. It has a crappy octopus which I regret buying. I do not regret buying the reg. The deepest I have had it so far was 153 ft, admittedly, but at that depth it was still a sweet breather.

I need to buy another reg for a tech class that I am taking. Because I like my current reg I am considering buying another one just like it. If I do, can I discard the crappy octo, and use the second stage from the new reg as an octo when I do purely recreational dives? According to what I've read so far, this should be no problem.

Can anyone talk me out of it WITHOUT talking me into an Apeks?

 

[canuckdiver]

I'm not absolutely sure, but I believe that the threads on the LP hoses should be the same, so there would be no problem using your micra as an octo on your new reg setup. Just double check with the LDS that the reg you are buying has standard threads on the LP ports and you shoud be fine

 

[Scubaroo]

You mean two Micra second stages on a single first stage? Sure. I swap my Apeks second stages between first stages - the IP of the first stages is the same, the second stages don't know the difference. But shh! don't tell them.

 

[My-way]

Yes you can swap octo regs between 1st stages.

The only concern is the tuning. As long as the intermediate ("IP") pressure is the same on the 1st stages then it is no problem. Even if it is not you can usually change the IP to suit.

Don't be put off by shops saying it is voodoo black magic you are dealing with.

 

[King_Neptune]

And don't give a Rats @$$ what anyone tells you about "How the Pro's Do it" .. or some other Uber-Macho-Garble! Once you find a good working combo that YOU like and YOU are comfortable with then stick to it!

It's you that has to be comfortable.

=-)

 

[rainreg]

The answer to the question is yes, but. you can use just about any 2nd stage as an octo with the current manufacture original reg, now the but part you should have the main spring which is what interfaces with the lp seat to an octo spring (these springs are generally a little tighter and increase WOB (work of breathing) sight to moderately depending on the manufacturer. The reason why the usual cracking pressure on an octo is slightly higher than a primary 2nd stage IE. (a primary 2nd stage cracking pressure range is @.3 to .9 where as the cracking pressure range on an octo is @1.0 to 1.2) this is so the 2nd stage does not free flow while not in use; and that is pretty much it when doing a change-out.

There is one other consideration that needs to be looked at and that is changing different manufacturers equip IE. A Poseidon 1st and 2nd with a USD octo, it can be made to work but, the Poseidon 1st and 2nd stage regs are high flow high IP, as with the USD oct is low flow, low IP, this mis-match can cause problems because the 1st stage supply pressure can overdrive the USD oct causing free flow as well as additional operational problems. So always try to stay with same manufacturer equip as well as know if your 1st and 2nd stages are High Flow or low flow.

rainreg

 

[raviepoo]

...between being a primary second stage on my secondary regulator for tech diving and being an octo for recreational diving with one tank and one reg. The second stage I want to use has manual adjustments to minimize the risk of freeflow at the surface. Would putting that switch on the minimum setting for use as an octo and opening it up for use as a primary resolve the problem?

rainreg once bubbled...
the usual cracking pressure on an octo is slightly higher than a primary 2nd stage IE. (a primary 2nd stage cracking pressure range is @.3 to .9 where as the cracking pressure range on an octo is @1.0 to 1.2) this is so the 2nd stage does not free flow while not in use; and that is pretty much it when doing a change-out.

rainreg

 

[Scubaroo]

raviepoo once bubbled...
...between being a primary second stage on my secondary regulator for tech diving and being an octo for recreational diving with one tank and one reg. The second stage I want to use has manual adjustments to minimize the risk of freeflow at the surface. Would putting that switch on the minimum setting for use as an octo and opening it up for use as a primary resolve the problem?

That's exactly what you do - it's probably the venturi control - putting it in the minimum position reduces freeflow. The only problem now is, when you donate the octopus to an out-of-air diver, the have a detuned regulator in their mouth - you're not going to remember to flick the switch in the possible mayhem of an OOA situation. Now the stressed OOA diver has a hard(er)-to-breath regulator in their mouth.

The solution to this is to use a long hose, donating the primary second stage from your mouth, so the stressed diver gets a fully functional regulator, not a restricted one, and you, as the donating diver, switch to the bungeed backup under your chin. As the least stressed diver, you can then deal with the reduced flow of the backup by flicking the switch - you've just had a lungful of air yourself, so the reduced flow isn't going to cause you as many problems - the reg may be perectly breathable on that setting, but only if you're calm - hand it to a stressed diver who was out of air who is going to be gulping off if it, and it may cause problems.

There is still no problem using two identical second stages on the same first stage - I do this with my ATX200s. I bought a pair I can use on double tanks, so I have two identical second stages - so I use them both. No problems using the method I described above.