PEX
Cross-linked polyethylene tubing that bends around corners and runs long distances without joints. Fewer fittings means fewer places to leak and faster installation, which is why it is common in repiping.
- Resists scale and corrosion from aggressive water
- More forgiving if water freezes in the line
- Must be kept out of direct sunlight and away from high heat sources
Copper
Rigid metal pipe joined with soldered or pressed fittings, used in homes for generations. It handles heat well and is not affected by sunlight.
- Long service life in suitable water
- Can develop pinhole leaks in some water conditions
- Higher material and labor cost
What usually decides it
Local code, the water chemistry, how much wall and ceiling access is needed, and budget. In a whole-house repipe, PEX often means less opening of walls. For short repairs, matching the existing pipe is usually simplest.