Quote: (Originally Posted by
Outlaw)
... personally iam still not that clear between balanced, unbalanced and fixed ip...
Thanks.
If memory serves, the Mk2 is an unbalanced piston 1st stage. The main purpose of balancing these is to enable a constant performance of the downstream valve (in this case) as the tank pressure decreases.
The performance of a Mk2 would probably be noticed if your using it for OC breathing, but I would venture that it's probably adequate regardless (never used one). For Rebreather purposes I'd expect it to be perfectly fine.
The Apeks is a balanced diaphragm that balances it's upstream valve by placing a balance chamber in the HP side of the orifice, effectively maintaining constant IP performance regardless of the tank pressure.
It's purpose here is, as mentioned above, the ease in which to modify it for constant IP, and hose routing. It's performance is over the top for Rebreather. The only time a difference between the two would be noticeable is on OC use. I also find getting parts for and servicing easy with the Apecs (never tried this yet with the Scubapro).