Short definition
Flexible copper tubing — also called soft or annealed copper — is copper sold in coils (typically 25, 50, 60, or 100 feet) that bends by hand or with a coil-spring tubing bender. It’s the standard for buried water-service lines (Type K, heavy wall), interior gas-line runs in difficult-to-fish locations, refrigeration, and short DIY supply work to icemakers and coffee machines.
What it is
Manufacturing-wise, flexible copper is identical alloy to rigid copper but annealed (heat-softened) to make it bendable. You can route it through tight cabinet spaces, around joists, and through wall cavities without fittings at every direction change — a major advantage in remodel work where pipe access is limited.
Flexible copper is sold in Type K (heavy wall, buried use) and Type L (medium wall, indoor and gas). Type M is too thin to be reliably annealed and is sold rigid only.
Why it matters to a homeowner
The most common DIY use is icemaker lines — a 25-foot coil of 1/4-inch soft copper, fed through cabinet bottoms with a saddle valve or compression tee at the cold supply. Beyond that, you’ll see flexible copper in:
- Buried water service replacement — Type K soft copper coiled into the trench, no joints between meter and house.
- Refrigeration and AC line sets — sold as ACR copper (same tube, dehydrated and capped for refrigerant service).
- Hydronic radiant supply runs — bent through joist bays without fittings.
The big installation rule: don’t kink it. A kink becomes a permanent flow restriction even after you straighten the tube. Use a coil-spring bender on anything 1/2-inch or larger and on any tight radius.
Common variants and what flexible copper is not
- Flexible (soft) vs. rigid (hard) copper. Soft is annealed for bendability and sold in coils; rigid is drawn-and-tempered straight lengths in 10- and 20-foot sticks.
- Type K, L, M. K is heavy wall (buried), L is medium (indoor and gas), M is thinnest (residential indoor only — sold rigid only).
- ACR copper. Same tube, sold dehydrated and capped for refrigerant service.
Common failure modes
- Kink at a tight bend — permanent flow restriction.
- External corrosion in damp underground installations without proper bedding.
- Pinhole leaks in old soft copper exposed to historically aggressive Cedar/Tolt water — Type K buried service lines have shown the failure pattern in some pre-1990 Seattle installations.
- Chafing where the tube passes through a stud or joist without a protection plate.