A Guide To Working With PEX Tubing

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PEX tubing has revolutionized plumbing renovations. PEX tubing can be fished through finished walls and ceilings like electrical wire.

Cross-linked polyethylene, commonly abbreviated PEX or XLPE, tubing has revolutionized doing plumbing renovations. Gone are the days when one had to rip out large sections of a finished wall to run concealed copper water pipe. With PEX and XLPE tubing, the water lines can be fished through finished walls much like electrical wiring. PEX is an installers dream, but it's not approved for use in all areas of the country or certain uses. Check the plumbing codes for using PEX in your area before using it for your next plumbing project.

Cross-linked polyethylene is available in sizes ranging from 1/4-inch to 4-inch. The most commonly used sizes are 1/2-inch, 3/4-inch and 1-inch.

What tools are needed to install PEX tubing?

  • Crimping tool

  • Reaming tool
  • Adjustable wrench
  • Screwdriver

If you are just getting started with PEX you will need to buy individual crimping tools, one for each size tubing. PEX crimping tools aren't inexpensive, and you can expect to pay approximately $125 to $150 for each one that you need. You may want to consider renting the tools you need. A single PEX crimping tool can be rented for less than $2 a day. Expect to leave a hefty security deposit, usually in the neighborhood of $110 per tool.

Materials and supplies needed

  • PEX tubing
  • Compression fittings
  • Crimp rings
  • Any special fittings or accessories that you might need for your specific project.

Types of PEX Fittings

When installing PEX tubing as part of a renovation project, use transition fittings to connect the PEX tubing to other types of pipes. Listed here are some of the most common types of PEX fittings.

Crimp Tee

Compression Tee

Compression Elbow

Composite Compression Tee

Composite Compression Stop Valve

Copper to Composite compression Tee

PEX crimp manifold

PEX crimp manifold with stop valves

Installing the PEX tubing

“New Work”

How you get PEX tubing from point A to point B, depends on where it is installed. Every situation will call for a different approach, so all I’m going to do here is providing you with some general tips.

If you are installing PEX while the walls are still open, you are in luck. All you have to do is drill holes through the wall studs and ceiling joists and pull the tubing though the holes. The rule is to use a spade bit size equal to twice the diameter of the tubing i.e. a 1-inch spade bit for a 1/2-inch tube. Like with nonmetallic sheathed electrical cable, PEX has to be protected against damage by nails and screws. Drill all holes so that near edge of a hole is at least 1 and ¼ inches from the near edge of the stud or joist. Drilling a hole so that the near edge of the hole is 1 and ¼ inches from the near edge of the framing member meets code requirements. I place a 1/16-inch thick steel nailing plate over the front of the stud or joist as an extra precaution.

Like with electrical cable, you can bend PEX tubing and fish it around corners in the wall plates. Make the bends as gradual as possible because sharp bends can cause the tubing to kink. Kinks cannot be removed, and you will need to replace a section of the tubing.

“Old Work”

It's easy to fish PEX tubing up through the space between studs using a wire fish tape. Running PEX tubing horizontally without causing serious damage to the wall finish cane be a real challenge. The easiest way to accomplish this feat and my favorite method is to remove the baseboard and cut a channel in the wall finish. The channel will be concealed when you replace the baseboard. Simply notch the studs, lay the PEX tubing in the notches and cover the notches with a steel nailing plate to protect the tubing from nails.

Using a PEX Manifold

PEX manifolds serve as distribution centers for water much as “Load Centers” do for electricity. If you are renovating a second floor flat and need to run new, hot and cold water lines for the kitchen, laundry room and bathroom, it's easier to install two manifolds and only have to fish two PEX lines all the way to the basement instead of three hot and three cold water lines.

Cut the PEX tubing in place

The easiest way to cut tubing to the correct length is to cut it after it's in place. The tubing can be cut with a knife but it's better to invest in a tubing cutter because they assure you of making the cut square. Square cuts are essential for making leak free compression connections.

Making a crimp connection

  1. Cut the PEX tubing with the tubing cutter to get a square cut.
  2. Carefully remove any burrs from the inside of the tubing using the reamer.
  3. Slip a crimp ring over the tubing and slide the tubing on the fitting.
  4. Grasp the crimp ring with the jaws of the crimping tool and squeeze the grips together until you feel the ring compress around the fitting.
  5. Tug on the connection to make certain it's a solid connection.


Apex Plumbing
Posted on Nov 25, 2013
Jerry Walch
Posted on Nov 16, 2010
Johnny Dod
Posted on Nov 16, 2010