Dumb question but I bought this http://www.homebrewhq.com/ProductDetails.aspx?productID=2059 and not sure where the o-ring should be. Right now I have it on the outside because it looks like it had a spot that is not threaded and I hear they seal better not being on threads. It's not leaking at the moment, but I had to really tighten it to get it to stop. I just wanted to be sure that it goes on the outside of the cooler. Did I do this wrong? I'm brewing in a few hours and don't want to leak out my mash.