The increase in the use of plastic as a pipe material to transport gas and water has been attributed to factors such as corrosion resistance, strength-to-weight ratio, lightness, flexibility and cost. One joining process for pipes is electrofusion welding. But defects can occur due to poor practices. Polytec, a project from the European Commission and The Welding Institute (TWI), based in Cambridge, UK, has resulted in in-manufacture, online, non-destructive, quality control of polyethylene electrofusion joints using ultrasonic phased arrays.