Material Copper

Image provided by Mueller Industries, Inc.

Copper is a long lasting, corrosion resistant, lightweight and strong material that involves minimal maintenance. When in contact with oxygen, copper forms a protective (patina) coating that renders it resistant to corrosion. Copper is the leading choice for plumbing, heating, cooling and other mechanical systems. Residential, commercial, and industrial buildings all utilize copper as a construction material for water and air conveying systems. All seamless copper tube manufactured in the United States conforms to standards set by the American Society for Testing and Materials (ASTM).

There are six standard types of copper tube:
1. Type K (green), is the heaviest wall and is used in higher pressure applications;
2. Type L (blue), has a medium wall and is used in mid-pressure applications;
3. Type M (red), has a lighter wall that Type L and is used in low-pressure applications;
4. DWV (for Drain Waste Vent, yellow), has the thinnest walled and used in drain, waste, vent applications with little to no pressure involved;
5. ACR (for Air Conditioning/Refrigeration, blue) used primarily in HVAC/R applications;
6. OXY/MED (blue, green) used for medical gas applications.

• Type K, L, M, copper pipe is used for domestic water, fire protection, solar, fuel/fuel oil, HVAC, snow melting, compressed air, natural gas, LP gas, and vacuum systems.
• DWV tube is used primarily in drain, waste, and vent, HVAC, and solar applications.
• ACR tube is used in air conditioning, refrigeration, natural and LP gas, and compressed air systems. 
• OXY/MED tube is used to deliver medical gas, compressed medical air, and vacuum systems.

Copper tube is manufactured in two distinct “tempers” or strength and hardness.  Drawn temper tube is “hard” tube, whereas annealed is “soft” tube. Hard tube is rigid like pipe while soft tube can be bent by hand. 

Soldering and brazing, used in combination with capillary fittings, is the most common method of joining hard copper.  Welding is also used, though it is far less common. 

“Soft” copper can also be joined by soldering or brazing, and is also connected using flare-type or compression fittings.  “Soft” copper can also be expanded (swaged) to fit over the end of another tube and joined in this fashion by brazing or soldering.

Copper tube is available in drawn (hard) lengths of up to 20 ft and annealed (soft) coils up to 100 ft.

Types K, L, M, DWV, and OXY/MED are standardized to have an outside diameter 1/8-inch larger than standard size designation. ACR tube is designated by actual outside diameter.


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