RV Camper RV Parts Waterless Trap, 1-1/2" BV1B/UB 1 1/2 No siphonage, no noise, no smells! Dry sealing valve prevents the escape of odors from your waste system into your RV and eliminates the need for check vents. Reduces pipe length, allows multiple branch connections and increases flexibility in location of fixtures. Includes waterless trap, valve and adapter kit. 1 per pkg.