PEX Piping
Updated February 20, 2026
Cross-linked polyethylene tubing that is flexible, freeze-resistant, and easy to install. The most popular choice for modern residential plumbing.
Overview
PEX (cross-linked polyethylene) has largely replaced copper for new residential water supply installations. Flexible, freeze-resistant, corrosion-proof, and dramatically cheaper than copper. Runs in long continuous lengths from a manifold to each fixture with fewer fittings and no joints inside walls. Three types: PEX-A (most flexible, expands for connections), PEX-B (stiffer, crimp connections), and PEX-C (least common). Red for hot, blue for cold, white for either. Cannot be used outdoors -- UV degrades it.
Pros & Cons
- Flexible
- Freeze resistant
- Easy installation
- Corrosion proof
- Affordable
- Not UV resistant
- Cannot be used outdoors
- Some fittings restrict flow
Key Features
- Flexible -- bends around corners without elbows, reducing fitting count
- Freeze-resistant -- expands up to 3x pipe diameter before bursting
- Corrosion-proof -- no pitting, scaling, or galvanic corrosion
- Runs in continuous lengths (up to 1000 feet per roll) for fewer joints
- Manifold systems allow individual fixture shut-offs from a central location
Sizing & Selection
3/4 inch for main trunk lines, 1/2 inch for branches to individual fixtures, 3/8 inch for short runs to single fixtures. Home-run (manifold) systems use 1/2 inch or 3/8 inch from the manifold to each fixture. Trunk-and-branch systems use 3/4 inch mains with 1/2 inch branches. Home-run uses more pipe but provides better pressure and individual shut-off capability.
Installation
PEX-A: expansion connections (Uponor/Wirsbo style). Expand the pipe end and ring, insert the fitting, the pipe shrinks back for a tight seal. PEX-B: crimp rings with a crimp tool, or cinch clamps with a cinch tool. Push-fit fittings (SharkBite) work on all PEX types. Support with hangers every 32 inches on horizontal runs. PEX cannot be directly connected to a water heater -- use 18 inches of copper or a braided connector at the heater.
Maintenance
- PEX is essentially maintenance-free inside walls. No corrosion, no scaling.
- Protect from UV exposure -- even indirect sunlight degrades PEX over time. Cover any exposed runs.
- Inspect accessible fittings annually for signs of dripping, especially crimp connections.
- PEX fittings slightly reduce the internal diameter at each connection point. Minimize fittings on long runs to maintain flow.
Buying Tips
- PEX-A is best for DIY -- expansion fittings are the most forgiving and the pipe is most flexible.
- PEX-B with crimp rings is the most common professional choice -- lower material cost, proven reliability.
- Buy a PEX manifold system if doing a whole-house install. Individual fixture shut-offs are incredibly convenient.
- Viega, Uponor, and SharkBite are the most trusted PEX brands. Avoid unknown brands -- fitting quality matters.
- Color code your runs (red hot, blue cold) even though white PEX works for both. Future you will thank present you.