Among non-metallic pipes, plastic pipes are the most widely used. There are many types of plastic pipes, divided into two categories: thermoplastic pipes and thermosetting plastic pipes. The thermoplastic pipes include polyvinyl chloride pipes, polyethylene pipes, polypropylene pipes, polyoxymethylene pipes, etc.; the thermosets include phenol plastic pipes. The main advantages of plastic pipes are good corrosion resistance, light weight, convenient molding, and easy processing. The disadvantages are low strength and poor heat resistance.