Can you actually see a tube of some sort under there with water draining out of it? The first thing that comes to mind is an overflow tube from the freshwater tank, but it would be very unusual for one to be that far toward the front. If that's what it is, the transfer valve that switches the freshwater input from house plumbing to the freshwater storage tank could be defective, continueing to fill the tank even though switched to house plumbing.
Joe & Annette
Sometimes I sits and thinks, sometimes I just sits.....
2002 Monaco Windsor 40PBT, 2013 Honda CRV AWD