oring types (again)

[scubaalblake]

I've read lots of post on orings and know all about hardness and type. I know Viton is 'good' for anything with Nitrox/O2.
The question is for non-Nitrox, non-O2, open-water SCUBA apps are 'ordinary' O-rings ok. My local hardware store sells neat little boxes of 160 assorted orings in various sizes for about $3. Can they be used for SCUBA at all?
I guess what I am saying is I know there are high-performance applications that need specific material but outside those applications are these 'ordinary' orings liable to be ok?

 

[pdh]

Although the o rings in your regs are just the normal o rings you would be able to buy, they would be an exact size designed by the manufacturer to fit the grooves in their regs. Tolerances for o ring fit are very exact, especially anything that slides. Although you could buy a bag of o rings for $3 it is unlikely that you would find the exact sizes required, even if they look and appear to fit the same. Also the manufacturer would be using o rings that would need to meet standards of quality that you may not get in a cheap bag in a hardware store. They may well appear to work fine, but as your life depends on nothing in your reg failing, I personally wouldn't risk putting anything in it that wasn't designed to be there.

That said, for non-life preserving kit - torches etc - you can probably get away with whatever fits and I have myself had to change an o ring in my BCD inflator at a remote dive site with one that I had from a reg servicing kit from the different manufacturer. It fitted and didn't leak and I used it until I could replace it rather than blowing the days diving. (Just to avoid the flames, I do class a BCD as life preserving kit but I also wear a dry suit which can lift me in the event of BCD failure and I can inflate orally if needed).

Paul.