How to Install Pex Tubing for Water Lines

PEX cross-linked polyethylene tubing is economical and easy to handle; consequently, many professional plumbers and DIY home builders have switched to PEX in favor of copper tubing. PEX is easy to install, less prone to freeze damage, and it's water-hammer resistant. PEX is supplied in 100 m spools, so it can be used for long piping runs and turn 90-degree corners. This means that fewer in-line couplings and right-angle elbows are required. In addition, this material can be easily connected to copper and CPVC tubing without using adhesives, solder or corrosive flux.

Economical PEX tubing is a viable alternative to copper pipe for household plumbing.

Things You'll Need

  • PEX tubing

  • Copper crimp rings

  • PEX crimping tool

  • PEX tubing cutter

  • Steel clamp rings

  • Ribbed pipe adapter

  • Copper tube

  • Handheld tubing cutter

  • Felt-tipped pen

  • PEX press-fit couplings

  • PEX compression fittings.

  • Adjustable wrench

  • PEX-a tubing

  • Pro-PEX rings

  • Wirsbo expander tool

  • Pro-PEX fittings

Crimp-Style Adapters

Step 1

Connect PEX to a wide variety of crimp-style adapters with copper crimp rings and a PEX crimping tool. Place a copper crimp ring over the squarely cut end of a length of PEX, insert a brass or plastic crimp-style adapter into the tube and position the jaws of the clamping tool over the copper crimp ring. Press the handles of the clamping tool together.

Step 2

Test the joint with the go/no-go gauge provided; if the ring doesn't fit into the "no-go" slot, but fits into the "go" slot, the joint is watertight to 200 lbs. per square inch of pressure.

Step 3

Clamp PEX tubing to crimp-style adapters with standard stainless steel clamp rings if this is the preferred method. Cut the end of the PEX off at 90 degrees with a PEX tubing cutter resembling a pair of pruning shears.

Step 4

Place a stainless steel clamp ring over the end and insert the ribbed pipe adapter. Position the clamp ring on the middle of the ribbed shaft. Place the jaws of standard ratcheted clamping tool over the lug on the crimp ring and squeeze the handles together several times until they won't move any further.

PEX to Copper Pipe

Step 1

Mark the cut line on the copper tube with a pencil. Place the pipe between the rollers and cutting blade of a handheld tubing cutter. Tighten the knurled cutting wheel knob. Rotate the cutter over the pipe three or four turns until there is no more resistance. Keep on tightening the knurled knob and rotating the tool around the pipe until it is severed.

Step 2

Cut the end of the PEX off square with a PEX tubing cutter. Mark a line 1 inch from the end on each piece of pipe with a felt-tipped pen.

Step 3

Insert the end of the copper tube into a special PEX press-fit coupling. Press the tube into the coupling until the marked line on the side of the tube reaches the lip of the coupling; you will feel the clamping teeth inside the coupling click into place. Repeat with the PEX side of the coupling to complete a watertight joint capable of resisting 200 psi.

Compression Fittings

Step 1

Connect PEX to manifolds, boilers and hot water heaters with PEX compression fittings. These fittings consist of three parts: an R20 or R25 threaded nut, a ferule and a tubing insert. Slide the threaded nut onto the tubing with the threads facing the end, place the ferule over the tubing and push the insert all the way into the tubing.

Step 2

Thread the brass connector nut onto a manifold or other plumbing devices inlet or outlet port, whichever is applicable. Tighten the hex connector nut with an adjustable wrench, but do not overtighten.

Step 3

Check the connection for leaks once water pressure is restored. If you detect a slight leak, tighten the brass hex nut a quarter turn and recheck; this should stop the leak. Repeat with another quarter turn if you still detect a leak, but don't go any further; overtightening will damage the rubber washer inside the compression fitting.

Step 4

Shut off the water supply and remove the leaking coupling. Clean up the mating surface on the appliance with a strip of 400-grit emery paper. Reconnect the coupling and retest,

PEX Expansion Joints

Step 1

Connect 1/2 inch PEX-a tubing to 3/4 inch PEX tubing with an expansion coupling as follows: Place a Pro-PEX ring around the end of your 1/2 inch PEX-a tubing, protruding 1/8 inch over the end.

Step 2

Screw the correct size head onto a Wirsbo expander tool. Insert the tapered head of the expander tool into the 1/2 inch PEX tubing. Bring the handles together to expand the tube. Continue bringing the handles together five to 15 times while rotating the tube.

Step 3

Remove the tool and quickly insert a 1/2 inch to 3/4 inch Pro-PEX fitting into the pipe. The 1/2 inch PEX-a tubing will then shrink back to its original size to complete the watertight connection.


Use PEX-a tubing for expansion fittings; ordinary PEX tubing will not shrink back to its original size.