I have a 1996 19 foot Travel trailer problem with the fresh water tank?

When I fill up the fresh water holding tank there is a hose that drains all the time. I can’t find a valve to shut it off. Does anyone know how to stop the water from draining.

Answerer

Odd question, as if we know more about a unnamed travel trailer than the owner does?

But if the water only leaves through the hose, then why not just put a valve on the end of the hose?