I think "bed" may have it. You don't say which TT you have but our 5th has 2 water connections next to each other. One for the fresh tank and the other for the black rinse.
I couldn't figure out why I wasn't getting any water after connecting the water.
Figured it out when the black tank geysered out the toilet.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks