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How to Install a PEX Plumbing System

Ed the Plumber explains the process of plumbing with PEX piping with these easy-to-follow instructions.

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Step 1: Drill Through the Stud and Sill Plate

Place the bit up to the stud and slowly start the drill, allowing it to build up speed.

Drill through the sill plate and sub-floor for each water line. When drilling through a stud, be sure that each hole is at the same level so the pipe runs parallel to the floor.

drill through sud and sill plate

Step 2: Run the Water Lines

Once the holes are drilled, start running the water lines. In most cases, the lines will come through the floor. In some cases, the lines will have to be run across the wall studs. When running the pipes through the studs, first be sure to drill the holes in the center so that when it's time to hang the wall board, the screws or nails don't reach the pipes and damage the pipes.

Note: Take this extra precaution -- Ed recommends using a nail plate. The nail plate has tacks on both ends of a flat piece of steel. Line them up to cover screws or nails so they don't penetrate the steel to damage pipes.

use nail plate as added precaution

Step 3: Pull and Secure the Lines

Pull the lines up through the holes drilled in the sub-floor (Image 1), and then run the other end to the area where the water will be coming into the home. Be sure to leave extra pipe on both ends of the run.

Secure the line to the joists using clamps (Image 2). Do your best to separate the hot and cold lines to minimize heat transfer.

Leave a little slack in the line to allow for expansion and contraction. Don't forget to label both ends of the line.

Step 4: Do the Rough Stub Outs

It's now time to do the rough stub outs for the sinks. A rough stub out is installing a special copper fitting that will adapt to the PEX. Notice at the end, there is a cap called a rough fitting, which allows you to charge up the system with air or water to test to see if there are any leaks. After the walls are up, you can cut off the cap and install the finish valves.

Tip: When roughing in the lines, use a right-angle drill with an auger bit or paddle bit.

Step 5: Apply Crimps

The crimps are the most crucial part of the project. If they aren't done right, the system could leak and cause problems down the line. There are two kinds of crimping tools. They both work pretty much the same, except one is more heavy-duty. If you're doing a lot of crimps -- use it.

For the perfect crimp, start by cutting the PEX and make sure it's straight. Slip a crimp ring onto the pipe, and then slide the pipe into the fitting. There's a little shoulder on all the fittings -- that's where you slide the PEX to. Use a pair of slip-joint pliers or your fingers to slide the crimp ring up. You'll know it's in position when it's between an 1/8" and 1/4" or closer to the end of the pipe. This step is crucial to ensure leak-free crimps. The crimp can't be further than a 1/4" or closer than 1/8" to the end. Position the crimping tool so it completely covers the crimp ring. Close the jaws as tight as possible.

crimps are most crucial part of project

Step 6: Rough in the Lines

Now it's time to rough in the lines to a fixture. Since you can't solder around the PEX piping, use a fitting called a PEX 90 that sweats right into place on a mixing valve. Once it cools from soldering, it can be safely connected it to the PEX water line.

It's crucial to take a mixing valve apart before soldering it. Remove any parts that might be affected by the heat from the torch. Use your standard soldering techniques when preparing the valve and fittings.

Step 7: Position the Fittings and Solder

Once prepared, position the fittings so that they both will face down when the valve is hung in place. Solder them into position. Be sure to let the valve cool completely before putting it into place.

position fittings and solder in place

Step 8: Connect the Water Lines

The water lines can now be brought up from the crawlspace and connected to the manifold. Position the manifold about eye level, and then screw the top mounting bracket to the studs. Make sure that it's level and secure. Attach the manifold to the bracket using the manufacturer's supplied screws. Install the bottom bracket to the manifold. Check to see that it's plumb before mounting the bracket to the studs.

connect water lines to manifold

Step 9: Mark and Drill the Holes

Align the template to the manifold on the studs and either mark each hole with a nail or drill directly into it. Continue down the line until all the holes are drilled.

Be careful not to damage the manifold with the drill. You may need to take the manifold down when drilling.

Step 10: Position the Ball Valves

With all of the holes drilled and the manifold mounted, attach the PEX ball valves to the manifold. Reach up, find the port and screw it into place. Get one of the lines and bring it up to the valve. This ensures that each fixture gets its own shut off valve.

When the ball valves are in place, pull the PEX lines up from the crawl space, being careful not to kink them.

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