Which is better—PEX or copper?
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PEX is available in long rolls or in short lengths for small projects.
PEX (cross-linked polyethylene)
has several advantages over
- 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
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
- 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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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
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
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
How do I splice PEX into my existing pipe?
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Stab-in tees are a fast way to connect PEX to copper.
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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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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 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.
Which tubing should I use for interior water lines?
For water lines, there are three grades: PEX-A, PEX-B
and PEX-C. They’re manufactured differently, PEX-A
being slightly more flexible. If you’re ordering online, go
ahead and spend a few cents extra for PEX-A. But don’t go
running around town looking for it; the difference isn’t that
big. The plumbers we talked to would be willing to use
any of the three types in their own homes. A good online
source for PEX tubing, fittings, tools and information
is pexsupply.com. PEX is also popular for in-floor
radiant heating systems, for which you need
PEX tubing with an oxygen barrier.
How do I connect PEX to my plumbing fixtures?
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PEX to copper stub-out to shutoff
Copper stub-outs work well for exposed supply-line connections.
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PEX to shutoff
PEX can be connected directly to shutoffs under a sink, but should be held in place with a drop-ear bend support.
There are several methods. 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 (first photo). You can
connect a compression-type shutoff
valve to the 1/2-in. copper stub-out
and then connect your fixture.
In areas that are concealed, like
under a kitchen sink or vanity cabinet,
you can eliminate a joint by
running PEX directly to the shutoff
valve. Use a drop-ear bend support
to hold the tubing in a tight bend
(second photo). There are several
types of shutoff valves that 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 raise the cost
much and is more convenient than
running downstairs to shut off the water when a repair is needed.
What about expansion?
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Don't pull it tight
PEX moves with changes in temperature, so leave it a little loose. For long runs you can add a loop to absorb movement.
PEX expands and contracts more
than copper, so don’t stretch it
tight. Let it droop a little between
fasteners. On long runs, it’s a
good idea to install a loop as
shown to allow for contraction.
Another advantage of the loop
is that if you mess up and need
a little extra tubing, you can
steal it from the loop. Also,
since PEX moves as it expands
and contracts, make sure to drill
oversize holes through studs or
joists so it can slide easily, and
don’t use metal straps to attach it. Use plastic straps instead.
Will PEX break or split if it freezes?
Probably not. Manufacturers are reluctant to say
so, but reports from the field suggest PEX can
withstand freezing. You should still protect the
tubing from freezing, but since it can expand and
contract, it's less likely to break than rigid piping.
What if I goof? Can I take it apart?
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Rotary tools make quick work of a bad clamp. Remove the cut clamp, then recut the tubing.
Sure—there’s a special tool for cutting off crimp rings, and you can use
side cutters to remove cinch clamps. But a rotary tool (Dremel is one
brand) fitted with a cutoff blade works great for cutting either type of
connector (see photo). After you remove the crimp ring or cinch clamp and
pull the PEX from the fitting, cut off the end of the tubing to get a fresh
section for the new connection. If you damage the fitting with the rotary
tool, replace the fitting rather than risk a leak.
Video: How to Glue PVC Pipe