The start of this thread was a warning about potential contamination of the fresh water tank from the toilet.
On my coach, this issue has been resolved. In the photo, you can see the braided line dedicated to the HeadHunter toilet now includes a check valve to prevent backflow from the toilet into the fresh water tank. There’s also a large ball valve that allows me to shut off the water flow to the toilet if the flush valve fails to close.
If you have a HeadHunter toilet in your coach, you should definitely have at least a check valve for safety. The check valve should use a spring to ensure it seats properly against backflow.