Which type of tubing is generally not used in a drainage system?

Type L copper tubing is generally not used in drainage systems primarily because it is designed and specified for applications requiring higher pressure and temperature ratings, such as water supply lines and heating systems. Type L tubing has a thicker wall than Type M, making it more suitable for hot and cold water distribution, rather than drainage, which usually handles lower pressure and wastewater.

In contrast, Type K copper tubing, known for its heavy wall, is used for underground and high-pressure applications, while Type M is the thinnest of the copper tubing types and is often used for lower pressure systems, including drainage. Plastic tubing, such as PVC or ABS, is commonly employed in drainage systems because it is lightweight, resistant to corrosion, and easy to install. Hence, while various types of copper tubing serve specific purposes, Type L does not meet the requirements for typical drainage applications.