[JRTJH]

The black tank flush connection on the outside of your RV runs to the black anti-siphon valve located under your bathroom sink, and from there down to the black tank where it's connected to the black tank spray assembly.

Here's a picture of the anti-siphon valve under the sink: The blue hose comes from the outside connection and the white hose goes to the tank sprayer... There is nothing (except a possible elbow connection) between the hose bib connector and the tank spray head except that pipe and the anti-siphon valve.