For me, this is one of the best features on the trailer.
I agree with the others.
Buy a grey hose to use just for the tank rinse.
A clear elbow on the sewer outlet allows you monitor your progress.
Here's a tip for you.
Do not leave the hose connected to the black tank rinse. Disconnect it after each use.
A friend of ours used to leave theirs connected the entire time they were at the camp site. (They stay at the coast for a month at a time)
Some body came along and turned it on while they were gone.
You can only imagine what happened. Black tank filling with water and valve closed. Only one place for it to go.
It ruined their rig and cause a major mess at the campgrounds.