You pretty much have the idea. It goes from the bib at the exterior wall to an anti siphon valve and then to the black tank.
It's not uncommon for the anti siphon valve to stick and when you turn on the water it's like a sprinkler head.
Cheap part and in my opinion that's the biggest problem with those. I've lost count of how many I have replaced on NEW units prior to delivery to retail customer.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.