After we filled our water tank and set up at the start our recent two week camping trip, my wife noticed a wet spot on the left side rear floor under the dinette.  We opened the water tank bench seat and saw puddles of water on the floor which we started sopping up and opened the drain cock the water tank figuring the tank was the problem.  The wet spot gradually extended itself to the right side back floor as well.  Opening the converter side bench we saw more water puddles, including the area under the converter which was live.  More sopping up.  Long story short:  the flange on the exterior fill vent which attaches to the tank intake pipe had split off and water went on the floor as well as the tank.  It wasn't easy to see this until unscrewing the water tank bench seat (thankfully not a hard job) and checking the flexible pipe feeding the water tank which easily came loose.  The way our hitch is mounted on truck slightly raises the hitch end of the trailer above the back end, so water had flowed from the water tank side to the converter side along the water/gas pipe path along the back floor into the converter side.   We carry collapsible water containers and a funnel with a plastic tube attached for getting water from hand pumps, so we were able to take off the bench seat, dry out, use the funnel assembly to refill the water tank and enjoy the rest of our trip.  Not sure why the flange had sheared off.   We just bought this used 2011 Scamp 19 this spring so maybe the previous owner had traveled with water in the tank and stressed the flange (??).  Back home I put on a replacement fill vent and replaced the connecting pipe.  We're off again this week for more cold weather camping.