PA Barns - My unit didn't have a gravity feed port too. I just posted a thread on this forum entitled Water Tank Sanitizing and Fill w/o Gravity Feed Port. This modification seems to work very well, and it solves two problems without carrying other equipment and it also avoids the potential mess.
There is one other potential solution that I found after making these mods that could be simpler and that's using the RV Antifreeze port and switching the City Water to Tank Fill in the water bay. Does the same thing back feeding the Water Tank as my thread w/o adding any mods. Wish I had found that thread earlier, but I searched on this site and several others without finding this potential simple and easy fix that apparently has been around for years. I haven't tried this old fix yet, but I've got a feeling that there is a check valve inline with the city water somewhere.
Ron, Cathy & Nuggett
2008 Winnebago Voyage 32H, & 2010 Subaru Forester
Everyone Remembers Nuggett