Pipe fittings and flanges made of polyvinyl chloride, or PVC, attach to pipe to convey potable water, corrosive liquids, and sewage in industrial and commercial applications. A numbered schedule rating is assigned to pressure-rated fittings. The greater the schedule number, the thicker and stronger the wall will be to withstand higher pressures. The walls of Schedule 80 fittings are thicker than those of Schedule 40, but not as thick as those of Schedule 100. PVC is a tough thermoplastic that can withstand UV rays, acids, alkalis, oils, and a variety of corrosive inorganic substances, making it resistant to sewage corrosive effects. PVC is a lightweight material that is nonflammable, has superior electrical insulation, and has smooth inside walls that resist scaling. PVC flanges and fittings are available in a variety of shapes and sizes.