4 Types of Copper Piping

Four different copper pipe types that can be used in your construction project

Copper Clean
Clean copper after it has been cut. Photo Cedarcityrecycling.com

Copper pipes are used normally in the construction industry for supply of water and as a refrigerant line in HVAC systems. However, there are many different types of copper piping with particular uses depending on how it is classified and where it will be installed. So, how do you know which is the right copper pipe that can be used? There are three major copper pipe types designated as Type K, L and M.

Copper pipes can be manufactured as soft or rigid copper and it is one of the preferred choices when doing residential and commercial construction due to its excellent corrosion resistance characteristics.

The actual outside diameter of a copper type is always 1/8-inch larger than the standard size and each type represents a series of sizes with different wall thicknesses. The actual OD of hard copper is always exactly 1/8" larger than the nominal size, in other words a 1/2" copper of K,L, or M is always exactly 5/8" OD. The type of copper piping suitable for any particular application is determined by the internal or external fluid pressure, by the installation, service conditions, and by local building codes. There is even a fourth type of copper pipe, but it is now used as frequently as the first three, but we will still describe it here. Recently there has been a trend to install PEX piping instead of copper but some contractors are still using the traditional piping.

Copper Pipe: Type K

Type K copper pipes have thicker walls than Type L and Type M for any given diameter. These type of pipes are normally used to water distribution, fire protection, oil, HVAC and many applications in the industry. It has not been approved to use Type K copper pipes in natural gas applications as the gas environment can damage the joints of the pipes.

K Copper pipe can use flared and compression fittings and it is available in hard and soft types. It is recommended when doing underground installation and for main water lines.

Copper Pipe Type L

Type L copper pipes are used on interior plumbing applications, fire protection and HVAC in some instances. Copper tubes of type L can be used with sweat, compression and flare fittings and it is available in hard and soft types. It can be classified as the most common type of copper piping as it can be used in many applications more than even Type K. Soft copper can be used to repair or replace old water lines, although hard tubing is more durable.It is often used outside the home, where it will be directly exposed. The walls of type L copper are thicker than the type M pipe walls.

Why Is Type M Different from L or K?

Copper pipe type M wall is thinner than type K and L walls. This type of copper pipe is used with flare fittings and can also be acquired in soft and hard tubing. It is used for on domestic water service and vacuum systems. Type M tubing is also very popular due to its price and because it is used to distribute water inside the house. Always check your building code on applicability and restrictions on copper pipe type.

DMV Piping

DMV copper pipe is a fourth type of tubing that is less commonly used. Its main use is on drains and it can also be found in old houses. It can be used also to vent plumbing fixtures, and should be used only in above ground applications. It has some yellow marks that help identify it from M type copper. 

K and L are available as hard or soft, but typically K copper is used for underground piping, because its thickness adds an extra bit of rigidity when back filling your pipe. DWV copper has a thin wall similar to M copper, its not designed for pressures over 10-15 psi.