I would just spin the ring off and raise it up to inspect the seal surface. You won't get it all the way out because of the plastic in the way but you can see the seal surface. I had mine out but I don't recall any issues with tightening it back up. Remember just holding it while..wait..I do remember it was a bitch getting the threads to start again. I had to mark the start of the threads on the tank and the ring and line them up otherwise it would cross thread...anyways..just held the center a little to the left of where I wanted to end until tight, then tapped the ring with a hammer and screwdriver until the ports where they needed to be. As I recall I don't think there is an actual seal there. I seem to remember the ring compresses the plastics together like a compression coupling.