PEX Piping: Everything You Need to Know

Which is better—PEX or copper?

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PEX tubing

PEX is available in long rolls or in short lengths for small projects.

PEX (cross-linked polyethylene) has several advantages over copper:

• PEX is cheaper than copper. Half-inch PEX tubing costs about a third the price of copper. Some of the savings will be offset by the need for a special tool to install the fittings, but if you’re doing a medium to large plumbing job, you’ll usually save by using PEX instead of copper.
• PEX is faster to install than copper. If you use a manifold and “home-run” system (shown below), it’s like running a garden hose to each fixture—super fast and easy. But even if you install PEX in a conventional main line and branch system, the connections are quicker to make than soldering copper.
• PEX won’t corrode like copper. If you live in an area with acidic water, copper can corrode over time. PEX is unaffected by acidic water and is therefore a better choice in these areas.

What about PEX vs. CPVC?

PEX and CPVC cost about the same. But there are a few reasons why PEX may be a better choice. First, PEX doesn’t require glue, which means you don’t have to work in well-ventilated spaces or wear a respirator. PEX is less likely than CPVC to burst if it freezes. Also, since PEX is more flexible and is available in long lengths, it can work better for “fishing” through walls in remodeling situations.

Do I need special tools?

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Connecting PEX

There are several ways to connect PEX; cinch clamps and copper crimp rings are the most practical for DIYers.

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Using a cinch clamp

Cinch clamp tools are simple to use and work for all sizes of pipe.

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PEX scissor cutter

The easiest way to cut PEX is with a special PEX cutter.

No. You can use stab-in or compression fittings to make the connections. But they’re too expensive to be practical on large projects. For most jobs, you’ll want to invest in a special tool to make connections. There are several PEX connection methods, but only two that are affordable enough to be practical for DIYers: crimp rings and cinch clamps, as shown above.

Crimp rings are a band of metal, usually copper, that you slip over the fitting and compress with a crimp ring tool. The main drawback to the crimp ring method is that you’ll need either separate crimping tools for 1/2-in. and 3/4-in. fittings, or a universal tool with a swappable insert (not shown). This adds a little up-front cost to this method. A combo kit with interchangeable crimp jaws starts at about $100.

Cinch clamps work more like the traditional band clamps you’re probably familiar with. You slip the cinch clamp tool (shown) over the protruding tab and squeeze to tighten the cinch clamp. The same tool works for all sizes of cinch clamps. Cinch clamp tools start at about $40. We like the one-handed version shown in the photo because you can hold the ring in place with one hand while tightening it with the other.

The only other special tool you need is a scissors-like cutter for the tubing.

How do I splice PEX into my existing pipe?

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Stab-in tee

Stab-in tees are a fast way to connect PEX to copper.

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PEX adapter

PEX adapters require soldering, but may be a better choice for buried connections.

There are several methods. The easiest is to cut out a section of pipe and slip in a stab-in tee (first photo). SharkBite is one common brand of stab-in fitting. This method doesn’t require soldering, which can be a big time-saver. But check with your plumbing inspector if you’re planning to bury this connection in a wall or ceiling. Some areas don’t allow stab-in fittings to be concealed. Another method is to solder in a tee and a PEX adapter. Then slip the PEX tubing over the adapter and attach it with your chosen connection method (second photo). You can also use a stab-in tee to connect PEX to CPVC. Read the label to find the compatible fitting.

Do I have to use manifolds with PEX?

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PEX manifold

Manifolds look intimidating, but they actually simplify plumbing runs and reduce possible leaks by eliminating the need for tees and other fittings between the main supply line and the fixture.

No. You can install PEX just like you would other pipe, with main lines and branches to each fixture. But you lose a lot of the benefits of PEX with this system since it requires so many fittings. With the home-run system, you install a manifold in the utility room or some area that’s close to the main water line and water heater, and run a separate PEX tube to each fixture as shown above. This system uses more tubing but is fast and only requires two connections: one at the manifold and another at the fixture end. You can also use a hybrid system where you run 3/4-in. hot and cold lines to a set of fixtures—for example, a bathroom—and install a smaller manifold behind an access panel. Then make short runs of 1/2-in. PEX tubing to each fixture.

Does it meet code?

There is no unified national plumbing code. Before starting your plumbing job, check with your local inspector for specific local requirements.

Do I have to use red for hot and blue for cold?

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PEX colors

PEX comes in red and blue colors to help you keep track of the hot and cold lines. You can use white PEX for everything if you prefer.

Is PEX reliable?

PEX has been used for decades in other countries, where there are thousands of homes with 30-year-old, leak-free PEX. Most of the problems with PEX systems (in the United States and elsewhere) have been caused by sloppy installation or faulty fittings rather than the tubing itself.

Can I connect PEX to my water heater?

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Water heater connection

PEX can't be directly connected to a water heater. First extend a pipe 18 in. from your water heater and connect the PEX to the pipe.