i did mine according to the specs of "the electric brewery"
I have a nut from Bargain fittings. I used an O-ring on the outside of the kettle and on the inside and it's leaking no matter how hard I tighten it. My specs gave a me a washer with an ID of 1 1/2" and the O ring I have is 1 7/17". I discovered that the O-ring actually fits inside the washer making the washer pointless. I was thinking about ordering a washer with a 1 3/8" ID so it will flatten the O-ring against the kettle.