1in easy plumb kit leaking.

[Jamesrg]

I have a Navien boiler that I used a easy plumb kit that I can't get to seal.
Had to take apart everything to move boiler is what caused the problems.
Now trying to put back together having troubles getting it to seal.
See pictures.
The bottom I get there is a o ring that should seal.
The top seems to be metal to metal with a plastic piece on top of the nut.
Just how tight should I be installing these.

 

[Dekzion]

The o ring should be proud of the surface and those two flat surfaces should have a fibre washer between them though you could in theory wrap the thread with some ptfe so that it laps onto the surface to act as a light washer