Which types of copper can be used within or underneath a building?

The use of copper types K, L, and M within or underneath a building is well-established in plumbing practices. Type K copper tubing is recognized for its durability and thicker walls, making it suitable for underground installations, especially in situations where greater pressure ratings and resistance to environmental factors are necessary. Type L, with moderately thick walls, is versatile and frequently used for both hot and cold water systems inside buildings, as well as for underground plumbing applications. Type M, although thinner than the other two, is still acceptable for residential water supply lines and can be used for various plumbing tasks.

These types of copper tubing are compliant with plumbing codes, which ensure safety and functionality in plumbing systems. In contrast, the other choices consist of materials or types that do not conform to the acceptable standards for use in plumbing installations under or within buildings. Therefore, knowing that K, L, and M are the recognized standards allows plumbers to confidently choose the right materials for their projects.