Which o-rings to use in Scubapro MK V first stage?

[The Danish Diver]

Hello out there all you fellow divers:cool2:

I could use some help on this issue: Which o-rings are to be used, of the different ones i just bought from Bigfoot Daisy on E-bay.
As seen on the picture of all the spares in the repair kit for the MK V regulator, there are different colors of o-rings. I take it that the materials of the o-rings are different hence the various colors!
Same question with the HP seats that comes in both a red and white versions?

Any help are graetly valued

Scubapro Mark 5 Piston Kit All Parts New Also Fits MK 1 MK 6 MK 7 MK 8 | eBay

The Danish Diver

 

[redacted]

The Mk5 schematic at this site is old enough to refer to those o-ring colors. While there may be some material differences, the colors are mostly to make the different o-rings more easily identified. Those colored o-rings are pretty old (20+ year) but most will still work fine. Next time buy new o-rings. The only one I would hesitate to use are the amber ones which can get a little crunchy with age. (The red one that goes on the metal orifice may have a similar problem.) Give them a squeeze and if they are still flexible, they should be OK. If the seat works, use it. Again you are looking at pretty old stock but they should last a long time. The few red seats I have seen, I have retired. I still have a number of the white seats (flat on both side so you can flit them to extend life) in service and working fine.

Oops, I had not looked at your link. Any of the seats should be OK. Just monitor IP often to detect any changes before they become a problem. I have seen those seat (original cave cone in red and white) in older regs that had started to deteriorate sending IP pretty high. Hopefully, that deterioration is influenced more by usage than age but I guess we will find out. It looks like there are two sets of piston head and piston shaft o-rings with the amber ones being urethane and the blue are probably buna. The piston shaft o-ring is subject to pretty high pressure and may have extrusion problems. The amber o-rings will resist the extrusion better as long as they are still supple. If you can instal it without damaging it, it should be fine.

This thread will give you more information on Scubapro o-rings: http://www.scubaboard.com/forums/repairing-your-own-gear/322518-scubapro-o-ring-sizes.html