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??