PEX (cross-linked polyethylene) is the modern standard for residential water supply lines, replacing copper for most new construction. Flexible, freeze-resistant, color-coded (red for hot, blue for cold), and connects with simple crimp or expansion fittings. The work is far easier than soldering copper — most homeowners can run PEX successfully.
This guide covers running PEX from a manifold or branch to a fixture, with the most common fitting type: crimp rings.
Before you start
Three things to settle:
1. PEX-A vs PEX-B vs PEX-C. PEX-A: most flexible, most expensive, expansion fittings (Uponor system). PEX-B: less flexible, cheapest, crimp fittings. PEX-C: rare. For DIY, PEX-B with crimp fittings is easiest and most affordable. Match fittings to PEX type.
2. Color-coded for hot and cold. Red PEX: hot water lines. Blue PEX: cold water lines. White or grey: either. Color is functional convention; some installations use white throughout.
3. Code requirements vary. Ontario allows PEX for residential. Some jurisdictions require licensed plumber for major plumbing changes. Check local code. Permit required for major plumbing work.
What you'll need
Tools
- PEX cutter (or sharp utility knife)
- Crimp tool with size dies (typically 1/2 inch)
- Tape measure
- Drill (for through-stud holes)
Materials
- PEX tubing (size as needed; 1/2 inch typical for residential supply)
- PEX fittings (compression-style, crimp-style — match your tool)
- Crimp rings (copper or stainless)
- Manifold or branch connection (depending on installation)
- Plumber's tape (for threaded connections)
Pro tip: support PEX every 32 inches
PEX bends and sags if unsupported. Use clip clamps or fastening straps every 32 inches max.
Code requires support; loose unsupported runs can fail.
Step-by-step instructions
Plan PEX route from source to fixture
Source: manifold (best for organized runs) or branch off existing main.
Route through framing — flexibility makes PEX easy to route around obstructions.
Plan support points every 32 inches.
Pre-drill any through-stud holes.
Shut off main water and drain
Main water shut-off at house entry.
Open lowest fixture in house to drain residual.
Bucket under work area for residual water.
Cut existing line for tap-in (if branch)
Pipe cutter on existing supply line.
Two cuts to remove section for T-fitting.
Or: cut into manifold dedicated branch.
Install T-fitting at branch point
PEX-to-copper transition (if existing is copper) or PEX-to-PEX T-fitting.
Crimp ring on each end of PEX.
Tighten compression on copper side.
Cut PEX tubing to length
PEX cutter (gives clean square cut).
Or sharp utility knife.
Don't crush or angle the cut.
Allow extra length for connections.
Slide crimp ring onto PEX
Copper crimp ring (or stainless) onto PEX end.
Ring should be near end of tubing but not on the very tip.
Position will be visible during fitting insertion.
Insert fitting fully into PEX
Push PEX onto barbed fitting until fitting's stop-collar.
PEX should completely cover the fitting's barbs.
Ring should be over the barbs (1/8-1/4 inch from end of PEX).
Crimp the ring with crimp tool
Crimp tool with proper die size (1/2 inch typical).
Position over the ring, squeeze handle fully.
Tool indicates crimp completion (some have visual indicator).
Verify ring is now compressed all around fitting.
Test gauge confirms proper crimp depth.
Run PEX to fixture and connect
Route PEX through framing, supporting every 32 inches.
Don't kink the tubing.
Connect to fixture's supply (typically threaded shut-off valve or compression fitting).
Apply plumber's tape on threads.
Restore water and test
Open main slowly.
Open shut-off at fixture.
Run water — verify flow.
Inspect each fitting for leaks (compression, crimp, threaded).
24-hour leak check
Paper towels under all connections.
Check next day.
Damp = slow leak; re-crimp or tighten.
Dry = solid install.
Common mistakes that cost you
- Wrong size crimp die. Crimp not full; leaks. Match die to tubing size.
- Kinked PEX. Restricts flow. Smooth bends only.
- Insufficient PEX over barbs. Fitting pulls out under pressure. Push tubing fully onto fitting.
- No support every 32 inches. Code violation. Loose runs sag and fail.
- Skipping crimp tool calibration. Calibration tool verifies crimp. Use it before any major install.
Frequently asked questions
Can I run PEX through floor joists?
Yes. Drill 5/8 inch holes through joist centers.
Don't drill near edges — weakens joist.
Cover holes through fire-rated assemblies (drywall ceilings) per Code.
PEX vs copper?
PEX: cheaper, easier, freeze-resistant, no soldering.
Copper: traditional, longer history, more rigid.
Modern best practice: PEX for new residential supply.
Some prefer copper for the visible main runs and PEX for branches.
Do I need a permit?
Minor changes: usually no permit.
New circuits or major plumbing changes: plumbing permit required.
Check local jurisdiction.
When to call us instead
PEX is part of every renovation we run. Our plumbers handle PEX runs, manifolds, and connections.
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