While using my black tank flush

Mine have all been completely separate hose connections. I'm having a hard time understanding why a black tank flush system would have any connection to the fresh water system due to the potential for crosss contamination.

I would immediately remove and eliminate your cross connection if you have one vs a cockpit error. Then sanitize all fresh water hoses and tanks with heavy bleach multiple times. Then I'd still be leary of the fresh water safety.