PEX Pipe
Flexible cross-linked polyethylene tubing widely used for residential water supply lines because it is easy to install and freeze-resistant.
PEX (cross-linked polyethylene) is a flexible plastic tubing that has largely replaced rigid copper and CPVC for residential water supply lines over the past two decades. Its main advantages are flexibility (it bends around corners without fittings), freeze resistance (it expands rather than splitting when water freezes), ease of installation in tight spaces, and lower material cost than copper.
There are three types: PEX-A (most flexible, expandable fittings), PEX-B (slightly stiffer, crimp or clamp fittings), and PEX-C (stiffest, cinch clamps). Fittings for PEX are made of brass, poly, or stainless steel and connect with crimp rings, clamp rings, or expansion rings depending on the type. PEX cannot be used outdoors because UV light degrades it.
A whole-house re-pipe with PEX typically costs $4,000–$15,000 depending on home size and access. PEX is accepted by all major building codes and is now the default choice for new residential plumbing in most of the United States.
Real-World Example
The plumber re-piped the 1960s ranch house with PEX-A, running individual "home-run" lines from a central manifold to each fixture for easy shutoff without affecting other fixtures.