Type K vs Type L vs Type M: Which Copper Pipe Should You Use?

Choosing the right copper pipe type is one of the most important decisions in any plumbing or HVAC project. The three main types — K, L and M — differ primarily in wall thickness, which affects pressure rating, cost and application suitability.

Type K — Heaviest Wall Thickness

Type K has the thickest walls of the three grades and is rated for the highest pressures. It is the standard choice for underground service lines, commercial installations and any application where the pipe will be buried or subject to physical stress. It costs approximately 20–25% more than Type L.

Type L — The Industry Standard

Type L is the most widely used copper pipe grade for above-ground domestic and commercial plumbing, heating systems, and HVAC. It offers an excellent balance of pressure rating, durability and cost. The majority of plumbing supply merchants stock Type L as their primary product.

Type M — Thinnest Wall, Lowest Cost

Type M has the thinnest walls and is the most economical option. It is suitable for low-pressure domestic applications such as hot and cold water supply in residential buildings. It is not recommended for underground use or high-pressure commercial systems.

Always check local building regulations before specifying pipe type. Requirements vary by country and application.