weldless water heating element in keggle

Hello - I am converting to electric (project details to come) and drilled a 1.25" hole in each of my 2 keggles. They are threaded heating elements with the bargainfittings 1" locknut on the inside w/ o-ring. Unfortunately, only 1 of my keggles has a tight seal. One has a slight leak out of it. I think it is due to the black rubber o-ring on the outside. What do most people use on their heating elements? The standard rubber o-ring? What can I do to mend that leak??

Thanks in advance!
Matt

I just monkeyed around with mine, until it stopped. I use a conduit star nut on mine, with no O ring, just the gasket that came on the element.

Wrap the threads in plumbers tape.

Wrap the threads in plumbers tape.

removed rubber gasket. leak stopped
I'm still going to wrap the threads. Thanks for the advice.