Small O-ring Red Sea Reefer skimmer

[Frans1992]

Hello,

I disambled my reefer skimmer, but now I have a very small o-ring and don't know where it was placed.

It's the o-ring in the middle. They don't describe it in the manual.
Can someone help me.

 

[blaxsun]

My best guess would be the post in "J" in the manual (this is where I have a tiny O-ring on my Nyos skimmer as well).