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Complete DIY Guide to Installing PEX Plumbing in a New House

Author: The Excellent LaborerTime: 2024-01-06 16:25:00

Table of Contents

Introduction to PEX Plumbing Installation

PEX, or cross-linked polyethylene, has become an increasingly popular option for residential plumbing in recent years. Offering flexibility, durability, and ease of installation, PEX allows DIYers to efficiently run water supply lines throughout a home. Before beginning a PEX installation, it is important to understand what materials are needed and how the system functions.

PEX is made by linking polyethylene polymer chains together to improve strength and flexibility. There are a few types of PEX piping, classified by the method used to cross-link the molecules. PEX-a uses peroxide, PEX-b uses silane, and PEX-c uses electron beams. The type focused on here will be PEX-b, which utilizes brass fittings that don't require any special expanding tools.

PEX Plumbing Overview

PEX tubing is available in both red and blue colors, with red typically signaling hot water lines and blue for cold. However, either color can be used interchangeably if desired. The flexible tubing allows for easier installation around corners and through studs compared to rigid piping. Supply lines are run from a central manifold or trunk line throughout the house to deliver water to fixtures and appliances. There are many advantages to using a PEX system over traditional copper plumbing. PEX is more freeze resistant due to its flexibility that allows the tubing to expand and contract without bursting. Installation is also much faster with fewer connections to solder or glue. And in the event a section needs replacement, repairs are simple by cutting out small sections rather than entire runs.

Tools & Materials Needed for PEX Installation

To install a complete PEX plumbing system, there are several key components needed:

  • PEX tubing - available in 100 ft rolls from big box stores like Lowe's and Home Depot. You can also sometimes buy 20 ft individual sticks.
  • PEX fittings - brass or plastic. Brass is generally better quality but costs more. You'll need elbows, tees, adapters, couplings, plugs, etc.
  • Copper crimp rings - to securely join tubing to fittings. Use 3/4" rings for 3/4" tubing or 1/2" rings for 1/2" tubing.
  • Crimp tool - essential to crush rings tightly onto fittings using pressure.
  • Tubing cutter - clean, straight cuts are critical. A simple ratcheting cutter works well.
  • Go/no-go gauge - confirms fittings are properly secured. Should come with your crimp tool kit.
  • Half-clamps - to anchor tubing to framing like floor joists while running lines.
  • Drill with 5/8" & 7/8" bits - for holes where tubing penetrates studs or plates.
  • Pressure gauge kit - attaches to PEX ends for testing completed system. Having all required tools and materials ready ahead of time ensures the PEX installation process goes smoothly from start to finish.

Installing PEX Water Lines Throughout the House

With the preliminary planning and prep work completed, it’s time to start running PEX lines throughout the house. Most systems utilize a central supply or manifold that functions as the main water trunk line. From there, separate hot and cold branches split off like strands of a spider web to supply water to all needed fixtures and locations.

Start by drilling any necessary holes where the main trunk line will penetrate walls and floors to access different areas of the house. Carefully feed the 100 ft PEX rolls through these openings as you go. Secure the tubing with clamps anchored to floor joists or wall studs approximately every 32”. Position lines to align with the pre-planned fixture supply points when possible.

Connecting PEX Pipes to Plumbing Fixtures

Once the main system lines are installed, separate branch lines can be run to connect specific fixtures like sinks, showers, appliances, exterior hose bibs, etc. When cutting any PEX tubing, ensure the ends are square for proper fittings.

Attach crimp rings and fittings to extend lines as needed. An example would be adapting from 3/4” tubing to 1/2” line with a reducing tee that then connects to valve supplies under a sink. Cold lines are stubbed out on the right side and hot lines on the left by convention. Make all connections in accessible areas instead of inside walls whenever possible.

Performing Pressure Tests on New PEX Plumbing

Before finishing walls or attaching fixtures, the newly installed PEX system needs to be pressure tested. This critical step identifies any leaks or issues that should be addressed immediately to prevent problems down the road once access becomes limited.

First, plug any open ends of tubing with plastic fittings made specifically for testing purposes. Connect a pressure gauge kit that enables pumping the system up to the required test pressure, typically around 100-120 PSI. Observe closely while under pressure for a period of time, usually 20-30 minutes minimum. If pressure drops indicate a leak, methodically check every connection and joint until located and fixed.

Successfully holding pressure without leaks demonstrates the PEX system was installed properly. Only after passing this test can you then move on to the final steps of finishing the installation.

Finishing Touches for a Complete PEX Installation

The last details must be buttoned up before the new PEX plumbing system is complete. Go back to any stubbed out lines at fixtures and trim them down to the correct height needed for mounting hardware or final connections.

It is also now safe to enclose lines running through walls by installing nail plates over them. This protects from accidental punctures by screws or nails later on. In a basement or crawlspace, any exposed main lines or drain piping can be insulated as desired to prevent freezing.

Finally, attach any special plumbing fixtures, backflow preventers, or accessories that were set aside earlier. Opening up the main water supply slowly to pressurize the system while checking for leaks one last time completes the process. Consult local permit agencies if an inspection is required before covering work.

Conclusion & Next Steps After Installing PEX

From beginning to end, PEX allows DIYers to tackle the entire plumbing system in their home as an achievable project. Understanding what tools are necessary, proper installation techniques, pressure testing, and finishing the system are the essential steps outlined above.

PEX plumbing provides many advantages over traditional materials that continue well beyond the initial work. The flexible lines hold up better against ground shifts, freezing temperatures, corrosion, scale buildup and more. And should any future leaks or repairs ever arise, PEX makes identification and replacement much simpler with minimal demolition.


Q: What are the benefits of using PEX over copper pipes?
A: PEX is more flexible, cheaper, and easier to install than copper pipes. It's also more freeze-resistant and durable.

Q: How do I cut and join PEX pipes?
A: Use PEX tubing cutters to cut the pipe cleanly. Join pipes using brass crimp fittings and copper crimp rings secured with a PEX crimping tool.

Q: What tools do I need for installing PEX?
A: You'll need a PEX crimper, tubing cutter, drill, crimp rings, fittings, clamps, a pressure gauge and adapter, plus basic tools like tape measure and marker.

Q: How do I pressure test new PEX plumbing?
A: Cap all pipes, connect hot and cold lines, attach a pressure gauge, pump system to 60 PSI, check for leaks over 15 minutes before releasing pressure.

Q: Should I use red and blue PEX tubing?
A: Red and blue PEX allows easy visual identification of hot and cold water lines, but using all one color tubing is also fine.

Q: Can I install PEX plumbing in concrete slab houses?
A: Yes, you can run PEX piping through concrete walls instead of stubbing pipes up through the floor.

Q: How do I secure PEX piping?
A: Use half-clamps nailed to joists or blocking to securely fasten PEX pipes in position against movement and vibration.

Q: Where do I install shutoff valves with PEX?
A: Install shutoff valves inline at fixtures and also on the main water line entering the house for emergency water supply shutoff.

Q: How long should supply lines be for sinks?
A: Leave 21 inches of exposed PEX supply lines above the floor to allow connecting the sink drain and faucet later.

Q: Can I run PEX tubing through exterior walls?
A: Yes. PEX is more freeze resistant than metal pipes, making it suitable for exterior garage wall installations.