We ended up installing a Valterra PVC tube for our sewer hose. The bumper on our Retro would not accommodate the better hose, after the first one leaked the second time we used it. We weren't sure if that was hose quality, or it scraped something in the close quarters of the bumper. The Valterra tube has caps that screw in. We still have the vented caps on the bumper. They aren't foolproof though. We lost one somewhere along the way, probably on, or after being on, an unpaved road.