Which type of copper tubing is the thinnest?

Copper tubing is classified into different types based on its wall thickness, which determines its suitability for various applications. Type K copper tubing has the thickest walls and is used primarily for underground water mains and other applications that require high pressure. Type L is thinner than Type K and is often used for water distribution, heating, and cooling systems.

Type M has the thinnest walls among the commonly used types, making it suitable for low-pressure applications such as residential water systems and above-ground installations. It is often favored for its lighter weight and lower cost compared to the thicker types, although it may not be ideal for high-pressure situations.

Type DWV (Drain, Waste, and Vent) is not categorized by the same wall thickness as Types K, L, and M but is used for drainage systems and has a different formulation and purpose.

Thus, Type M copper tubing is the thinnest and is useful in specific residential plumbing contexts where high pressure is not a concern.