"Rob Turk" wrote

That would get me back to the starting situation; What do I use to seal
the bushing, considering nothing seems to stick to polyethylene..

I think part of the problem here, is that everyone does not know exactly
what you are working with, such as:

Is the location of the fitting in the tank built up at all, or is it like
someone just punched a hole in the tank in a random location, and stuck the
fitting in?

Can you give us a part number, or picture on a site, or at least a
description of the type of fitting that is penetrating the tank that you are
presently using, that is not working?
--
Jim in NC