PEX (Cross-Linked Polyethylene)
Affiliate link — we may earn a commissionPEX is a flexible plastic tubing used for residential water supply lines. It bends around corners without fittings, resists freezing better than copper (it expands and contracts), and installs faster because you crimp or clamp connections instead of soldering. PEX comes in three types: PEX-A is the most flexible and can be expanded with a fitting then shrunk back (Uponor/Wirsbo system). PEX-B is slightly stiffer and uses crimp rings. PEX-C uses the same fittings as PEX-B. Colors are standardized: red for hot, blue for cold, white for either. You cut PEX with a ratcheting PEX cutter, not a saw.
Why It Matters
PEX has replaced copper in most new residential construction because it costs less, installs faster, and handles freeze-thaw cycles better. If you're replumbing a house or adding a bathroom, PEX runs in a fraction of the time that copper takes. The one limitation: PEX can't be exposed to UV light. Don't run it outdoors or through unfinished spaces where sunlight hits it.