# Copper tubing
**Copper tubing** is seamless tube made of nearly pure copper, manufactured to standardized wall-thickness schedules and used to convey water, gas, refrigerant, and medical gases in plumbing, heating, cooling, and related systems. In the United States, water tube is manufactured to [ASTM International](https://www.edgepedia.org/astm-international) specifications, principally ASTM B88, the Standard Specification for Seamless Copper Water Tube, which covers copper UNS No. C12200 suitable for general plumbing and commonly used with solder, flared, or compression-type fittings.[1](https://store.astm.org/b0088-02.html) Plumbing tube and fittings make up the second-largest use of copper, after electrical applications.[2](https://archive.copper.org/publications/newsletters/innovations/2001/08/intro_to_copper.php)
| Key fact | Detail |
|---|---|
| Material | Tube supplied to the ASTM tube standards is a minimum of 99.9 percent pure copper, customarily phosphorus-deoxidized and designated UNS C12200 (DHP copper)[3](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf) |
| Governing standard | ASTM B88, Standard Specification for Seamless Copper Water Tube; fittings for soldered or brazed connections are described in ASME B16.18 and B16.22[1](https://store.astm.org/b0088-02.html) |
| Wall-thickness types | Three basic wall thicknesses for water tube: Type K (thickest), Type L (intermediate), Type M (thinnest); separate DWV drainage tube and ACR air-conditioning tube[4](https://archive.copper.org/applications/plumbing/techref/tpf_stds/tube_pipe_stds.php) • [3](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf) |
| Size convention | Types K, L, M, DWV and Medical Gas tube use ASTM standard sizes in which the actual outside diameter is always 1/8 inch larger than the size designation; ACR tube is designated by actual outside diameter[3](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf) |
| Color coding | Drawn-temper tube carries a color stripe: green for Type K, blue for Type L, red for Type M, with incised markings at intervals not exceeding 1.5 ft[4](https://archive.copper.org/applications/plumbing/techref/tpf_stds/tube_pipe_stds.php) |
| Drinking-water compliance | Manufacturers certify copper tube and fittings to NSF/ANSI 61, the health-effects standard for materials in contact with drinking water[5](https://www.copper.org/applications/plumbing/cth/design-installation/cth_3design_gencon.html) |
| Recyclability | Copper pipe and tubing is 100 percent recyclable, and end-of-life recycling credits materially lower its life-cycle environmental totals[6](https://www.copper.org/publications/newsletters/discover/2007/spring/pdf/dc_spr2007.pdf) • [7](https://www.rehva.eu/rehva-journal/chapter/comparative-lca-of-water-installation-tube-systems-based-on-copper-pex-al-and-pex) |
## Standard types and tempers
Seamless copper water tube is manufactured in nominal sizes from 1/4 inch through 12 inch. Types K and L are produced in drawn temper (hard) straight lengths from 1/4 through 12 inch and in annealed temper (soft) coils from 1/4 through 2 inch, while Type M is produced only in drawn temper from 1/4 through 12 inch.[4](https://archive.copper.org/applications/plumbing/techref/tpf_stds/tube_pipe_stds.php) Temper describes the strength and hardness of the tube: drawn temper is called hard tube and annealed temper soft tube. Hard tube is usually joined by soldering or brazing with capillary fittings or by welding; soft tube can be joined the same ways and is also commonly joined with flare-type and compression fittings.[3](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf) Annealed tube suits flared or compression fittings provided the tube ends are rounded and sized where needed; Types K and L in the drawn temper are suitable for certain types and sizes of compression fittings.[1](https://store.astm.org/b0088-02.html)
All tube must be permanently marked (incised) to show the tube type, the manufacturer's name or trademark, and the country of origin; hard tube additionally carries this information printed in a color that distinguishes its type.[3](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf) Beyond the water-tube types, the principal classes of copper tubular products include Type DWV drainage tube under ASTM B306 and medical gas tube under ASTM B819.[8](https://www.copper.org/applications/plumbing/overview/cu_alloy_tube_pipe.php)
## Selecting a type for the application
The designer selects the tube type for a given application, and plumbing and mechanical codes govern what may be used. The Copper Development Association's minimum recommendations include: Type M hard tube for underground water services joined with fittings and Type L soft tube where coils are more convenient; Type M for water distribution systems above and below ground and for chilled-water mains of all sizes; Type DWV for above- and below-ground waste, soil and vent lines, roof and building drains and sewers; and Type L soft temper for radiant panel and hydronic heating and snow-melting systems where coils are formed in place, with Type M where straight lengths are used.[9](https://archive.copper.org/applications/plumbing/cth/select-tube/cth_2select_recom.php)
Wall thickness affects pressure capacity but, above about 1-1/4 inch size, there is virtually no difference among Types K, L, and M in friction pressure loss, because the differences in cross-sectional area become insignificant as tube size increases.[10](https://archive.copper.org/applications/plumbing/cth/design-installation/cth_3design_size.php) In system design, tube, fitting, and joint ratings must be considered collectively, since the lowest of the ratings governs the maximum installation design pressure.[8](https://www.copper.org/applications/plumbing/overview/cu_alloy_tube_pipe.php)
## Installation and joining
Copper tube is joined by soldering, brazing, welding, and a range of mechanical joints that assemble without the heat source required for soldering and brazing.[3](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf) The assembly of copper plumbing or fire sprinkler systems by soldering is described in ASTM Practice B828; solders for potable water or fire sprinkler systems are covered by Specification B32, and acceptable fluxes by Specification B813.[1](https://store.astm.org/b0088-02.html) Annealed tube in coils permits long runs without intermediate joints, which reduces the number of connections in a system.[5](https://www.copper.org/applications/plumbing/cth/design-installation/cth_3design_gencon.html)
Because thermal expansion must be accounted for in design: a 100-foot run of tube, whatever its diameter, will lengthen by 1.128 inches when warmed 100 °F, going from 70 °F at room temperature up to 170 °F.[5](https://www.copper.org/applications/plumbing/cth/design-installation/cth_3design_gencon.html)
## Corrosion in potable water
The primary source of copper in drinking water is corrosion of copper pipes, which are widely used for interior plumbing in the United States; corrosivity toward copper depends primarily on the pH of the water, with very low pH values associated with the highest levels of copper corrosion by-products.[11](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10152ZA.txt) Under the U.S. Lead and Copper Rule, tap-water concentrations of lead and copper must be below action levels of 15 µg/L and 1,300 µg/L respectively.[5](https://www.copper.org/applications/plumbing/cth/design-installation/cth_3design_gencon.html)
Corrosion takes two broad forms. Uniform corrosion of copper in potable water is usually quite low, based on the long service life of most tubing; from World War II to 1972 over 6 million miles of copper plumbing tube was put into service, with relatively few cases of actual failure.[12](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100CILD.TXT) Localized corrosion includes pitting, impingement, and under-deposit attack. Pitting is not widespread but draws attention because practically new pipe can fail in a short time, and failures occur at random locations even within one distribution system.[12](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100CILD.TXT) A U.S. survey by Cohen and Lyman of the Copper Development Association found pitting almost invariably associated with cold, hard well waters, with a typical aggressive well water containing greater than 5 ppm dissolved carbon dioxide, dissolved oxygen up to 10 to 12 ppm, and chlorides and sulfates; they reported that pitting can be prevented by treating the water to neutralize dissolved carbon dioxide.[12](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100CILD.TXT)
Copper is also more susceptible than most engineering metals to impingement attack, a flow-velocity-dependent localized corrosion aggravated by entrained solids or gas bubbles. Prevention is achieved by limiting flow velocity to 5 feet per second for most municipal waters, and to considerably lower values when entrained solids or air bubbles are present.[12](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100CILD.TXT)
## Copper versus plastic alternatives
[Cross-linked polyethylene](https://www.edgepedia.org/cross-linked-polyethylene) (PEX) pipe has become a viable alternative to copper for residential water plumbing, and several life-cycle assessment (LCA) studies have compared the two. In a case study of a student housing project in [Lancaster, Pennsylvania](https://www.edgepedia.org/lancaster-pennsylvania), Asadi and colleagues found that using PEX instead of copper would reduce the total life-cycle cost of the building by up to 63 percent and carbon dioxide emissions by approximately 42 percent; initial material cost savings were $97,346, about 4.61 times the price of the PEX, and labor installation savings were $12,364.88, with copper piping taking more than twice as long to install.[13](https://www.sciencedirect.com/science/article/pii/S0959652616311313)
A European LCA of drinking-water installation systems for a 100 m² apartment, critically reviewed by an external panel of three independent reviewers under [ISO 14040](https://www.edgepedia.org/iso-14040)/44, reached a different balance. For the production-and-end-of-life modules (A+C), the copper system showed lower global warming potential, 36 kg CO₂ equivalent, than PEX at 44 kg and PEX-Al at 46 kg CO₂ equivalent. Including module D credits from recycling, copper's net total fell to 25 kg CO₂ equivalent against 38 kg CO₂ equivalent for both PEX systems. Materials and their fabrication dominate 85 to 90 percent of the life cycle in all three systems, and copper's closed-loop scrap market makes its recycling credits a state-of-the-art market situation rather than a hypothetical one.[7](https://www.rehva.eu/rehva-journal/chapter/comparative-lca-of-water-installation-tube-systems-based-on-copper-pex-al-and-pex) The two studies differ in scope, geography, and functional unit, so their results are not directly comparable; together they show that copper's environmental standing depends strongly on whether end-of-life recycling credits are counted.
## Service-line replacement and other uses
Copper water tube manufactured to ASTM B88 is the primary copper-related component in lead service line replacement in the United States, where utilities replacing lead pipes typically install copper or plastic lines.[14](https://downloads.regulations.gov/EPA-HQ-OW-2023-0396-0070/attachment_1.pdf) • [15](https://apnews.com/article/0472f18fef32ef3519dda651f36fb5fc) In marine service, copper and copper alloy tube carry potable water, seawater, and other fluids, with the chief application being alloy tube bundles for condensers and auxiliary heat exchangers.[16](https://copper.com.au/resources/plumbing/) Copper's thermal conductivity also suits it to heat exchangers, piping, and components in cryogenic plants and other low-temperature applications.[9](https://archive.copper.org/applications/plumbing/cth/select-tube/cth_2select_recom.php)
## References
1. [ASTM B88-02, Standard Specification for Seamless Copper Water Tube, ASTM International](https://store.astm.org/b0088-02.html)
2. [Innovations: Introduction to Copper: Applications, Copper Development Association](https://archive.copper.org/publications/newsletters/innovations/2001/08/intro_to_copper.php)
3. [Copper Tube Handbook, CDA Publication A4015-24/23, Copper Development Association](https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf)
4. [Copper & Copper Alloy Tube and Pipe Standards, Copper Development Association](https://archive.copper.org/applications/plumbing/techref/tpf_stds/tube_pipe_stds.php)
5. [Copper Tube Handbook: III. Design Data, Copper Development Association](https://www.copper.org/applications/plumbing/cth/design-installation/cth_3design_gencon.html)
6. [Discover Copper, Spring 2007, Copper Development Association](https://www.copper.org/publications/newsletters/discover/2007/spring/pdf/dc_spr2007.pdf)
7. [Comparative LCA of Water Installation Tube Systems based on Copper, PEX-Al and PEX, REHVA Journal](https://www.rehva.eu/rehva-journal/chapter/comparative-lca-of-water-installation-tube-systems-based-on-copper-pex-al-and-pex)
8. [Plumbing: TechCorner, Copper & Copper Alloy Tube and Pipe, Copper Development Association](https://www.copper.org/applications/plumbing/overview/cu_alloy_tube_pipe.php)
9. [Copper Tube Handbook: II. Minimum Recommendations for Various Applications, Copper Development Association](https://archive.copper.org/applications/plumbing/cth/select-tube/cth_2select_recom.php)
10. [Copper Tube Handbook: III. Pressure System Sizing, Copper Development Association](https://archive.copper.org/applications/plumbing/cth/design-installation/cth_3design_size.php)
11. [Technical Factsheet on Copper, U.S. Environmental Protection Agency](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10152ZA.txt)
12. [Corrosion in Potable Water Systems: Final Report, U.S. Environmental Protection Agency](https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100CILD.TXT)
13. [Asadi, S., Babaizadeh, H., Foster, N., Broun, R. (2016). Environmental and economic life cycle assessment of PEX and copper plumbing systems: A case study. Journal of Cleaner Production 137: 1228–1236](https://www.sciencedirect.com/science/article/pii/S0959652616311313)
14. [Lead Service Line Replacement Components – Copper Tube, Regulations.gov docket attachment](https://downloads.regulations.gov/EPA-HQ-OW-2023-0396-0070/attachment_1.pdf)
15. [The push to remove lead pipes is on, Associated Press](https://apnews.com/article/0472f18fef32ef3519dda651f36fb5fc)
16. [Plumbing, International Copper Association Australia](https://copper.com.au/resources/plumbing/)
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*Topic: Encyclopedia › Technology and the built world › Architecture, buildings, and civil works › Civil and water works › Water supply, sanitation, and flood control › Water supply systems and conveyance › Network components and appurtenances › Pipes, water mains, and service connections*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license