A type of pipe is an airtrap, which is a seven-letter word. It is a device used to prevent air from entering a system, such as a water supply. PVC is another type of pipe, which is a three-letter word. It is a type of plastic that is commonly used for plumbing and drainage systems. DUCT is a four-letter word and is a type of pipe that is used to transport air, gas, or liquid. Lastly, INFLOW is a six-letter word and is the process of a substance entering a system.