After having Campingworld install our washer/dryer we began experiencing gray water odor while driving. We inspected the installation and found they had not installed a trap in the vent and they gave us a difficult time about it. We insisted they install a trap, but in Arizona, it doesn't take long for evaporation. So before a trip, we run the washer for a few seconds and then cancel the cycle to drain the machine. We also installed a cone thingy for the top of the main gray vent.