RV Sewer Cap: YELLOW MALE FOOTLOOSE Odor proof foot operated self-closing sewer cap with 3.5" internal and external threads. Fits 4" threaded coupling. Enviro Design Products creates durable monitoring well and RV sewer caps. We manufacture sewer products including the Footloose Sewer Cap and Gator hose restrictor, for the purpose of installing, protecting, and operating the RV campground industry. Recommended by State and County regulatory agencies. Watertight Sewer Pipe Cap. Overnight Sewer Hook up. Incredibly durable sewer cover built to withstand the harshest enviromental conditions.