What is the difference between type L, M, and K copper pipes?

Copper pipes are classified by wall thickness. The three main types used in Quebec are:

Type K: Thickest wall (0.049 in for ¾ in). Used for underground water service and high-pressure applications. Service pressure: up to 1,250 PSI at 70°F. Color: green.

Type L: Medium wall (0.035 in for ¾ in). Most common in residential for potable water (hot/cold supply). Service pressure: up to 1,000 PSI. Color: blue. Cost: approximately $4/ft for ½ in.

Type M: Thin wall (0.025 in for ¾ in). Indoor use for low-pressure hot/cold water. Not allowed for gas or underground water service. Service pressure: up to 850 PSI. Color: red.

CMMTQ practical rule: For residential potable water, use Type L for durability. Type M is acceptable for non-critical indoor lines. Type K is required for buried water services.