Introduction
This article explains the three types of copper tubing, covering its composition, key properties, grades, standards and typical applications. Copper tube is produced in a range of grades, tempers and sizes that are selected by the service: water distribution, air conditioning and refrigeration, heat exchange, fuel lines and medical gas systems. This article explains how copper tube types are defined and how to choose the right specification.
Copper Tube Types by Application
The common families are water tube, ACR tube and general engineering tube. Water tube is covered by ASTM B88 in types K, L and M with different wall thicknesses, ACR tube by ASTM B280 in drawn tempers with a dry internal atmosphere, and general tube by ASTM B75. In Europe the corresponding standard is EN 1057, and in China GB/T 18033 covers water tube and GB/T 1527 drawn tube.
Type K, L and M Explained
The letter type denotes wall thickness at a given outside diameter. Type K has the thickest wall and the highest pressure rating, Type L is the general-purpose plumbing wall, and Type M is a thinner economical wall for low-pressure systems. The same outside diameter is used for all three so that fittings are interchangeable, and the wall selection is driven by the working pressure of the system.
| Type | Wall | Typical Use | Standard |
|---|---|---|---|
| K | Thickest | High pressure, underground | ASTM B88 |
| L | Medium | General plumbing | ASTM B88 |
| M | Thin | Low-pressure systems | ASTM B88 |
| ACR | Drawn | Refrigeration lines | ASTM B280 |
Tempers and Forms
Tube is supplied in drawn tempers for ACR service, which gives the strength to hold shape and resist vibration, and in annealed coils for plumbing, which bends easily and can be snaked through framing. Straight lengths, coils and pancake coils are available, and internally grooved tube is used for enhanced heat transfer in evaporators and condensers.
Joining and Standards
Copper tube is joined by brazing, soldering, flaring and mechanical press fittings. The tube grade must be compatible with the joining method, and phosphorus-deoxidized grades such as C12000 and C12200 are preferred for brazed systems because they are immune to hydrogen embrittlement.
Selection Checklist
Determine the working pressure and temperature, select the type and temper, confirm the grade and standard, and check the surface condition and internal cleanliness before installation.
