Most sewer pipes are generally made of plastic materials such as PvC and polyethylene. They provide for the exiting of wastewater materials from kitchens, baths and laundries to a sanitary sewer or septic tank system. The majority of residential sewer systems have pipes that rely on gravity systems where slight inclines in the piping allow for the flow of sewage to a further distribution point. These pipes consist of joints and fittings that can become damaged and leak. Sewer leaks can lead to unsightly odors and major messes.