PEX Piping Installation Guide
Comprehensive guide for installing PEX plumbing systems. Learn about PEX types, connection methods, manifold systems, and proper installation techniques.
Estimated Time
Varies by project
Tools Required
8 items
Materials Needed
8 items
PEX (cross-linked polyethylene) plumbing has revolutionized residential plumbing with its flexibility, durability, and ease of installation. PEX costs less than copper, installs faster, and resists corrosion and freezing better than traditional rigid piping. The flexible tubing snakes through walls and under floors without joints, reducing leak potential and water hammer noise.
First developed in Europe in the 1960s and approved for use in U.S. plumbing in the 1980s, PEX now accounts for over 60% of new residential water supply installations. Three types exist: PEX-A (most flexible and expensive), PEX-B (most common), and PEX-C (least expensive but stiffest). All meet the same ASTM F876 and F877 standards for performance.
PEX installation is an excellent DIY project because it requires no soldering and uses simple mechanical connections. A whole-house repipe that might take professional plumbers 2-3 days with copper can be completed in one long day with PEX by a skilled DIYer. The specialized tools (PEX cutter and crimping or expansion tool) pay for themselves quickly in saved labor costs.
Safety Precautions
- Always turn off the main water supply before cutting into plumbing
- Wear eye protection when cutting PEX and operating crimping tools
- Keep PEX away from hot surfaces - it can melt at high temperatures
- Don't expose PEX to direct sunlight during storage - UV degrades the material
- Use only approved PEX fittings and connection methods
- Test all connections at full pressure before closing walls
- Follow local plumbing codes - not all areas permit PEX for all applications
- Ensure adequate support - PEX can sag without proper hanging
Tools Required
- PEX cutter
- Crimping tool or expansion tool
- Drill with bits
- Tape measure
- Tubing bender
- Deburring tool
- Marking pen
- Adjustable wrench
Materials Needed
- PEX tubing
- PEX fittings
- Crimp rings or expansion rings
- Manifolds (if applicable)
- Mounting brackets
- Insulation sleeves
- Shut-off valves
- Adapters for transitions
Preparation
Choose Your PEX Type and Connection Method
PEX-A expands and contracts the most, making it most forgiving during installation and freeze conditions. PEX-B offers a good balance of cost and performance. PEX-C is budget-friendly but stiffer. For connections, crimp rings (requires crimp tool) are most common, expansion fittings (requires expansion tool, only works with PEX-A) are fastest and most reliable, and push-to-connect fittings (no tools) are easiest but most expensive.
Plan Your Distribution System
PEX enables two distribution designs. Traditional trunk-and-branch runs a main line (3/4 or 1 inch) with branches to fixtures, similar to copper. Home run systems use a manifold with individual 1/2-inch lines running directly to each fixture. Home run systems use more PEX but provide better pressure, easier shutoffs for individual fixtures, and fewer connections, reducing leak potential. Manifolds cost $50-150 but greatly simplify layouts.
Calculate PEX Quantities
Measure all runs from the water heater and main line to each fixture. Add 15-20% extra for bends, mistakes, and future repairs. PEX typically sells in 100-foot coils (red for hot, blue for cold, white for either). Buying in bulk coils costs less than short pre-cut lengths. Don't forget to count fittings: elbows, tees, reducing unions, and adapters to fixtures.
Installation Steps
Install the Manifold System (if using)
Mount the PEX manifold in an accessible location near your water heater and main shut-off valve. Common locations include basements, utility rooms, or large closets. The manifold should be mounted securely to wall studs at a comfortable working height.
Connect the manifold inlet to your main water supply using a 3/4 or 1-inch line. Install shut-off valves between the main line and manifold for maintenance. Similarly, connect the hot water manifold to the water heater output.
Each manifold port serves one fixture. Label each port clearly as you connect lines: "Kitchen Sink Hot", "Master Bath Shower Cold", etc. This labeling makes future troubleshooting and maintenance infinitely easier.
Install ball valves on each manifold port if they're not already integrated. These allow shutting off individual fixtures without affecting the whole house.
Pro Tips:
- Choose a manifold with more ports than you currently need for future additions
- Install the manifold where it's protected from freezing in cold climates
- Consider a manifold with integrated pressure gauges for troubleshooting
Run PEX Lines to Fixtures
Starting from the manifold or main trunk line, run PEX tubing to each fixture. PEX's flexibility means you can snake it through existing walls via small holes drilled through studs. Drill holes in the center of studs, at least 1.25 inches from edges, to leave room for protective nail plates if required by code.
Support PEX every 32 inches horizontally and every 4-6 feet vertically using approved hangers or brackets. Don't use metal hangers that can rub and wear through PEX over time - use plastic hangers or add cushioning.
Keep hot and cold lines at least 6 inches apart when running parallel to prevent temperature transfer. When crossing, insulate hot lines or maintain separation.
Avoid kinking PEX by bending it gradually. PEX-A can handle tighter bends (roughly 6 times the pipe diameter), while PEX-B and PEX-C need gentler curves. Use PEX-specific bending supports for tight turns rather than fittings.
At fixture locations, leave 6-12 inches of extra PEX coiled behind walls for future adjustments or repairs. Stub out the PEX and cap it temporarily while completing other runs.
Pro Tips:
- Color-code your lines: red for hot, blue for cold, white for either
- Take photos of PEX runs before closing walls for future reference
- Mark PEX locations on floor plans or take detailed notes
- Use a stud finder to avoid accidentally drilling into wiring or existing pipes
Warning:
- Never run PEX through cement slabs - use barriers or approved tubing systems
- Keep PEX at least 6 inches from recessed lights and other heat sources
- Some local codes prohibit PEX in certain applications - verify before starting
Make Crimp or Expansion Connections
For Crimp Connections: Cut PEX squarely using a PEX cutter (never use a utility knife). Slide a crimp ring onto the PEX, ensuring it's 1/8 to 1/4 inch from the end. Insert the fitting completely into the PEX - you should see the fitting barbs through the translucent pipe. Position the crimp ring 1/4 inch from the pipe end, centered over the fitting barbs. Place the crimping tool over the ring and squeeze firmly until the tool releases. The ring should be compressed evenly all around. Use a go/no-go gauge to verify the crimp is correct.
For Expansion Connections (PEX-A only): Cut PEX squarely. Insert the expansion tool head into the PEX end and squeeze to expand it. Remove the tool and immediately insert the expansion fitting - work quickly as the PEX contracts within seconds. The PEX will shrink tightly around the fitting, creating a superior connection. No verification tools needed.
For Push-to-Connect Fittings: Cut PEX squarely and deburr the cut end. Mark the insertion depth on the pipe. Push the fitting onto the pipe firmly until it reaches the mark - you should feel it click into place. Test by pulling firmly on the connection. These fittings are more expensive but require zero special tools.
Test each connection by slowly pressurizing the system and checking for leaks before moving to the next connection.
Pro Tips:
- Practice on scrap pieces before making final connections
- Buy extra fittings - mistakes happen and you'll want backups
- Expansion connections are strongest but require PEX-A and a more expensive tool
- Keep connections accessible where possible for future inspection
Connect PEX to Fixtures and Existing Plumbing
At fixture locations, use drop-ear elbows or other approved PEX-to-fixture adapters. These typically have PEX connections on one end and threaded outlets for fixture connections on the other. Secure drop-ear elbows to wood blocking behind walls.
When connecting PEX to existing copper or galvanized plumbing, use brass transition fittings. Never connect PEX directly to threaded connections - always use a threaded PEX adapter. Apply Teflon tape to threaded connections.
At the water heater, connect PEX using brass or copper adapters threaded into the heater. Install shutoff valves between PEX and the heater for future maintenance.
For outdoor hose bibbs, transition back to copper for the last few feet since PEX degrades in sunlight. Use a copper stub-out with a frost-free hose bib.
Warning:
- Never use compression fittings without checking manufacturer compatibility with PEX
- Don't connect PEX directly to water heaters - use 18 inches of copper or brass first to handle heat
Pressure Test and Inspect
Before closing any walls or covering PEX runs, pressure test the entire system. Close all outlets and fill the system with water. Pressurize to 80-100 PSI (or 1.5 times working pressure) using your water supply or a test pump.
Maintain this pressure for at least 2 hours while carefully inspecting every connection for leaks. The pressure should not drop more than 5 PSI over this period in a sound system.
Mark any leaking connections, drain that section, and remake the connection. Retest until all leaks are eliminated.
Many jurisdictions require inspection of PEX installations before covering. Call for inspection before closing walls if required by your permit.
After passing all tests, flush the system thoroughly by opening all fixtures and letting water run for several minutes. This clears any debris from installation.
Pro Tips:
- Take photos of all connections during the test for your records
- Test sections as you complete them rather than waiting to test the entire system
- Use soapy water on connections to reveal tiny leaks that don't drip
Common Mistakes to Avoid
- Kinking PEX around sharp corners instead of using fittings or gentler bends
- Not supporting PEX adequately - it sags over time without proper hangers
- Using copper crimp rings instead of stainless steel - copper corrodes and fails
- Over-crimping or under-crimping connections - both cause leaks
- Not using a go/no-go gauge to verify crimps - faulty crimps fail later
- Exposing PEX to sunlight during storage or installation - UV degrades it quickly
- Mixing incompatible connection methods on the same line
- Not leaving enough slack for future repairs and thermal expansion
- Connecting PEX directly to water heaters without transitioning to metal first
Tips and Tricks
- Buy a quality PEX cutter - clean square cuts are essential for good connections
- Rent expensive tools like expansion systems if doing a one-time whole-house repipe
- Use manifold systems for new construction - they're much easier to install
- Label everything extensively - you'll thank yourself later
- Keep detailed photos and drawings of PEX routes before closing walls
- Buy PEX in bulk 100-foot coils for significant cost savings
- Consider insulating hot water PEX lines to reduce heat loss and save energy
- Use PEX expansion tools if budget allows - they make the strongest connections
When to Call a Professional
Consider hiring a professional plumber if:
- Your local code prohibits homeowner plumbing work or requires licensed plumbers
- You're uncomfortable cutting into existing plumbing or shutting off water mains
- The project requires extensive demolition or reconstruction you can't handle
- You discover problems like corroded pipes or damaged framing during the project
- You need to connect to complex systems like radiant floor heating
- Time constraints prevent completing the project quickly (exposed plumbing is a problem)
- You're working in difficult spaces like crawl spaces or tight attics
- The installation requires coordinating with other trades like electricians or carpenters
Code Considerations
PEX plumbing installations must comply with plumbing codes:
- Approval: Verify PEX is approved in your jurisdiction - some areas still restrict its use
- Standards: Use only PEX meeting ASTM F876 and F877 standards
- Connection Methods: Only use approved connection methods (crimp, expansion, compression, or push-fit)
- Support Requirements: PEX must be supported every 32 inches horizontally and 4-6 feet vertically
- Nail Plates: Required where PEX passes through holes closer than 1.25 inches to stud edges
- Hot Water: Some codes limit PEX use near water heaters - maintain specified distances or use metal piping
- Outdoor Use: PEX cannot be exposed to sunlight - transition to approved materials for exterior applications
- Inspection: Many areas require inspection of PEX installations before covering
- Permits: Plumbing permits typically required for PEX installation projects
Maintenance Tips
PEX is Remarkably Low Maintenance
- PEX doesn't corrode, so it requires virtually no maintenance once properly installed
- Insulate PEX in unconditioned spaces to prevent freezing (PEX can freeze and thaw several times without bursting, but repeated freeze cycles can eventually damage it)
- Check connections annually in accessible areas for any signs of weeping or moisture
- If you notice pressure drops, check for crimps that may have loosened over time
- Protect PEX from rodents in crawl spaces - they occasionally chew through plastic pipes
Expected Lifespan
PEX is rated for 50+ years of service when properly installed. It outlasts copper in corrosive water conditions and doesn't develop pinhole leaks like copper can. The connections are typically the weakest point - properly made crimp and expansion connections should last the life of the system.
Cost Estimate
DIY Material Costs
- PEX tubing (1/2-inch, per 100-foot coil): $40-70
- PEX tubing (3/4-inch, per 100-foot coil): $70-120
- PEX manifold (8-12 ports): $50-150
- Crimp rings (per 25): $8-15
- PEX fittings: $1-5 each depending on size and type
- Transition fittings to copper/fixtures: $3-12 each
- PEX hangers and supports: $0.25-0.75 each
Tool Costs (One-Time Investment)
- PEX cutter: $15-40
- Crimp tool: $40-150 (ratcheting models are better)
- Go/no-go gauge: $5-15
- Expansion tool: $150-400 (consider renting)
- Hole saw set: $30-60
Typical Whole-House Repipe
- DIY material costs: $1,500-3,000 for average 3-bedroom home
- DIY total with tools: $1,800-3,500
- Professional installation: $4,000-8,000
Potential Savings: DIY PEX installation saves $2,500-5,000 compared to professional copper or PEX installation. The tools pay for themselves on a whole-house project, and PEX costs 25-50% less than copper materials alone.
Related Installation Guides
Water Heater Installation Guide
Complete guide for installing electric and gas water heaters, including tankless models. Learn proper sizing, venting, and safety requirements.
Whole House Water Filtration System Installation
Install a whole-house water filtration system for clean water throughout your home. Covers sediment filters, carbon filters, system sizing, and maintenance.