SonexBuilders.net

pfhoeycfi wrote:Be sure to check the most recent rev of the Sonex oops fitting installation instructions where it says not to use the outside o ring.

Hmm, I missed that instruction. Though I did turn a nice little O-ring groove on the nut. Seems to have worked fine.

When I installed mine about 9 or 10 years ago, I also machined a groove for the O-ring in the underside of the nut. Without that, turning the nut tends to force the O-ring out to the side. The outer O-ring does nothing to aid sealing. Its elimination also means that less material has to be ground off the mound on the inside of the tank to get the fitting to reach far enough through to properly install the nut. Some folks some years back started using flat fiber washers on the outside in place of the O-ring. The one thing the O-ring accomplishes is making the fitting slightly more tolerant of having the inside surface not exactly parallel to the outside surface of the tank. but that is a problem that can be addressed with a bit more work with smoothing of the inside mound if found necessary, but is a reason to be sure to orient your drill perpendicular to the outside surface of the tank when drilling out old fittings.

David A.