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How to Connect Pex Pipe

DEAR TIM: I've got a major bathroom remodel I'm jumping into and luckily I'm allowed to do the plumbing work myself where I live as long as it meets code. My inspector says I can use pex pipe and it seems too good to be true. I've never worked with pex piping and have some experience sweating copper tubing. What's involved in working with pex pipe and can you share some tips? How do you transition between copper tubing and pex pipe? I'm worried that the pex piping is harder to work with than it looks. Bob S. Nashua, NH

DEAR BOB: I've been a master plumber for over thirty-five years and for many of those I was licensed. I've always loved plumbing, and I clearly remember when pex pipe was breaking into the marketplace. It was one of those technology breakthroughs that puts your head on a swivel.

There are many advantages to pex over copper. The biggest one, in my opinion, is you usually only have two connection points and they're almost always visible. Since the pex pipe is flexible much like electric cables that are hidden behind your walls, you just drill the needed holes in joists and wall studs and feed the pex tubing as one long piece from your basement mechanical room to the plumbing fixture that needs the water. It's caveman simple to run the pipe.

You're going to love working with pex pipe. Everything about it is faster. You can cut pex pipe with a handy cutting tool in less than two seconds. The tool makes a superb clean cut that's required to get watertight joints. It takes much longer to cut a piece of copper tubing, including reaming the cut end. I can probably cut ten or more pieces of pex in the time it takes me to cut just one piece of copper.

Here are different pieces of pex pipe, fittings and a cool cordless expanding tool that allows you to make connections in seconds. Photo credit: Tim Carter

Here are different pieces of pex pipe, fittings and a cool cordless expanding tool that allows you to make connections in seconds. Photo credit: Tim Carter

Pex connects to fittings, valves and manifolds by simple compression. The plastic used to make pex pipe has a memory. It's much like Spandex fabric. You can stretch and enlarge pex pipe, but it wants to go back to it's original size and does so in just seconds depending on the air temperature. You stretch pex pipe using a special expander hand tool, or you can use a very nice cordless expanding tool that will do all the work for you.

When you get ready to make a connection with pex pipe, all you have to do is slide a compression ring onto the end of the cut pipe. You then insert the expanding tool in the end and give it a squeeze. The tip of the tool starts to open and it stretches the pipe and the compression ring. You'll need to squeeze the tool several times to get the pipe and ring to enlarge enough to fit over the end of the fitting, valve or manifold.

As the pex pipe starts to shrink back to its original size, it grabs tightly onto ridges on the fittings and valves. The pex pipe digs into these ridges making a watertight connection. When you create your first connection, you'll think it's magic. The best part is at normal room temperature of about 70 F, you can create a connection from start to finish in about 15 seconds or less. That's impossible to do if you're trying to solder a copper pipe joint. That takes minutes of preparation and work.

Here are some pex fittings and a faucet shut-off valve. Photo Credit: Tim Carter

Here are some pex fittings and a faucet shut-off valve. Photo Credit: Tim Carter

It's very simple to transition between pex pipe and copper tubing. All of the pex pipe manufacturers make solid brass fittings that allow for the transition. You solder this brass fitting onto the end of a piece of copper tubing as you'd solder any joint. Once the fitting has cooled to room temperature, be sure to clean off the soldered joint to remove any residual flux that can cause future corrosion.

The other end of the brass fitting has the same sharp ridges as you find on the plastic fittings. Simply slide a compression ring on the end of your pex pipe, use the expander tool to enlarge the pipe and ring and then slide it over the end of the brass fitting. Within seconds the pex pipe and ring shrink and you've got a watertight connection.

Temperature affects the pex pipe. The warmer it is, the easier it is to enlarge the pipe and compression rings with the expander tool. If you're working in a cold location, keep the compression rings in your pocket or inside your clothes to keep them warm.

When you use the expander tool, always rotate it slightly with each squeeze. This helps keep the pex and the compression ring in a circular shape instead of an oval. You'll discover if you have to make up lots of joints, the cordless expanding tool will save your hands. But if you only have to do a few joints in a day, then the hand expander tool will be just fine.

I would practice making up just a few joints with small pieces of pex pipe to start. You'll discover very quickly how many squeezes you need to give the tool to expand the pipe and compression ring enough to slide over the fittings and valves. You'll also see how fast the pex shrinks to make the watertight connections.

Be sure any holes you drill in studs and joists meet all code requirements. Don't drill the holes so small that the pex pipe just fits. You want some wiggle room between the pipe and the sides of the holes. Place the holes with thought so nails and screws you'll use for drywall, trim lumber, etc. will not puncture the pipe. Use metal protection plates in places where it's a strong possibility that the pipe and fasteners will be in close proximity.

CLICK HERE to watch a short video on connecting pex pipe.

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