Hi,
I have a schematic for a 31 ft rear bath which should be your Excella from a reprinted manual I got from EBAY years ago. This manual has been a lifesaver for my '68 Globetrotter when I repaired my plumbing system. Its marked 1980 but the layout seemed to be the same as mine so if it looks the same go with it. I will try to email a scanned copy for you.
Let me know if it works for you.
Regards,
Randy
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