Hi how are you doing. I just purchased a 10sd and had the similar problem. Underneath the sink inside of a cabinet they have a plastic water trap kind of like the thing you seen your house. I'm not sure why you would need a water trap in a camper it just seems kind of weird. I purchased a fitting similar to the one from the hose coming from the sink and the one on the end of the hose that goes to the drain outside the bottom of the camper. I joined those two together and bypassed the water trap and it drains like a champ. Hope it works for you good luck