You probably have the 4 Way Anderson Valve in the Universal Docking Center (UDC), which means you should have 2 overflow drains - one on each side of the trailer. There's probably a PEX line running along the outside of the frame, terminating in a 90 degree PEX fitting.
I've attached a picture from a Bighorn showing where the overflow comes out of the water tank and goes through the frame. Yours should be similar. This picture was taken before they attached the PEX line that runs along the frame.