Copper Pipe

Copper pipe is the most common metal pipe used for residential water supply lines in North America. Introduced as a replacement for galvanized steel in the 1950s and 1960s, copper became the dominant supply pipe material due to its corrosion resistance, long service life, ease of installation, and antimicrobial properties. While PEX has displaced copper in much new construction, tens of millions of homes still rely on copper supply systems.

Copper pipe types (ASTM B88)

• Type K (thickest wall): the heaviest-duty copper — used for underground service lines, high-pressure commercial applications, and outdoor burial. Marked with a green stripe.
• Type L (medium wall): the standard for residential interior supply plumbing. Marked with a blue stripe. Works with all copper joining methods (solder, compression, push-fit, press-fit).
• Type M (thin wall): the lightest residential grade — acceptable by code for most above-grade interior supply applications. Lower cost than Type L. Marked with a red stripe. Less suitable for high-pressure or aggressive water chemistry.
• DWV copper: the thinnest gauge — for drain-waste-vent applications only (no pressure).

Joining methods

Copper can be joined by: soldering (the traditional method — flux + torch + lead-free solder); compression fittings (no tools, no heat); push-fit fittings (SharkBite); or press-fit fittings (a crimping tool compresses a copper ring — fast, no torch, common in commercial work).

Service life and failure modes

Type L copper lasts 50–70+ years under normal conditions. Failure modes: pinhole leaks from aggressive water chemistry (low pH, high chloramine, or certain groundwater); erosion corrosion in high-velocity situations (undersized pipes, sharp elbows at high flow); electrolytic corrosion where copper contacts dissimilar metals without a dielectric union.

Copper vs. PEX

PEX is faster to install, immune to freeze-thaw damage (it's flexible), and costs less in materials. Copper remains the preference for visible supply lines (aesthetics), outdoor above-grade runs (PEX degrades in UV), and in water systems with chemistry that degrades PEX fittings. Both are code-compliant for residential supply.