PEX piping is the biggest revolution since the flush toilet. Learn what it is and everything in between with this install PEX plumbing guide.

What is PEX Piping?

PEX piping or cross-linked polyethylene pipe costs less than half the price of copper and installs much faster. And since it’s flexible, PEX makes remodeling jobs easier. PEX has a strong “memory;” it always wants to spring back to its original shape. So working with a coil of PEX is like wrestling with a giant Slinky.

For most jobs, you’re better off buying 10-ft. “sticks” instead. You may have to pay a few cents more per foot and install a coupler or two, but you’ll avoid frustration and kinks. Even plumbers who run miles of PEX every year often buy sticks than coils.

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How Do I Connect PEX to my Plumbing Fixtures?

If the connection will be visible, like under a wall-hung sink, and you would prefer the look of a copper tube coming out of the wall, use a copper stub-out (left). You can connect a compression-type shutoff valve to the one-half-inch copper stub-out and then connect your fixture.

In concealed areas, like under a kitchen sink or vanity cabinet, you can eliminate a joint by running the PEX supply directly to the shutoff valve. Use a drop-ear bend support to hold the tubing in a tight bend (right). Several types of shutoff valves connect directly to PEX.

If you’re using a manifold system with valves, you may not need to install a shutoff valve at the fixture. Ask your plumbing inspector. We recommend adding one, though. It doesn’t increase the cost much and is more convenient than running downstairs to shut off the water when a repair is needed.

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How to Install PEX Pipe?

To make watertight connections with PEX pipes, you’ll need the right tools and supplies. For each of the following methods of connecting, the fittings and connectors must be an exact match to the size of the PEX pipe.

Hundreds of types of fittings, usually brass, are available for connecting PEX to existing copper or steel pipes and for making connections to fixtures.

Fittings are also available for connecting pipes of different sizes. The following five methods are used for making the connections watertight.

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Compression Fittings

This type of PEX fitting involves slipping a threaded brass nut over the end of the PEX tube, followed by a tapered plastic compression ring (view on SupplyHouse). A hollow brass tube is then inserted into the end of the PEX tube.

The whole thing is inserted into the end of a threaded fitting, and the threaded brass nut is then screwed onto the end of the fitting. As the nut is tightened, it squeezes the plastic compression ring against the end of the brass fitting to create a seal.

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Push-Fit Connections:

The quickest way to connect PEX is with the push-fit method, which involves purchasing special push-fit fittings that “grab” the end of the PEX pipe when inserted over the end. No special tools are required to use push-fit fittings, but a special removal ring is required to remove them from the end of the pipe once you’ve connected it.

As a child, if you ever played with one of those paper tube “traps” that grabbed your finger when inserted into the tube, you get the idea of how push-fit connecting works.

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