Next time you need to replace pipes in your home, consider an alternative to rigid piping that comes in rolls, can be cut easily to any desired length, and requires no soldering and very few joint fittings. Generically called PEX-AL-PEX, this flexible plastic piping is so easy to install that you can handle most projects quickly on your own.
Although PEX-AL-PEX is relatively new to North America, it’s approved in major plumbing codes, and professional plumbers are increasingly choosing PEX-AL-PEX because of its successful 30-year track record in Europe. It’s a little more expensive than rigid copper piping — but the advantages outweigh the extra cost. Plus, you can save money by doing the job yourself. You can buy it at major hardware stores, where it’s usually sold as water supply piping and infloor radiant-heat lines. When you buy PEX piping at the hardware store, make sure the tubing is stamped with “NSF-61” or “NSF pw” (for potable water), which distinguishes it from the PEX that is used only for infloor radiant heating applications.
PEX-AL-PEX is named for its sandwich-layered construction that uses cross-linked polyethylene plastic as the outside layer (PEX), aluminum as the middle layer (AL) and another layer of cross-linked poly on the inside. To keep it simple in this article, I’ll refer to PEX-AL-PEX as just PEX, though that name also is used for plastic-only water supply lines.
PEX is worth considering for your next plumbing project for three reasons:
Flexibility. PEX can be hand-bent in any direction and will remain in a fixed position. This allows you to work it around and through existing floor joists, walls and frame members. PEX bends tightly up to a 3-inch radius without forming kinks, which significantly reduces the need for most elbow joints.
Easy joint assembly. PEX joints usually are made with either threaded compression fittings or crimp-on-connection rings. These joints are fast and easy to complete, and you don’t have to torch and solder them, except when you connect new PEX lines to existing copper supply pipes. But even connecting copper pipes to PEX is a job that most people can do themselves — all it takes is some basic knowledge of plumbing skills and PEX joints.
Resistance to frost cracking. PEX piping is better than rigid piping at resisting the outward pressure of freezing water. Manufacturers typically test and warrant their aluminum-core PEX lines to withstand five freeze/thaw cycles before cracking may occur. PEX may withstand even more than that, but it isn’t completely immune to frost cracking.
Octopus Manifold & Fittings
To get the most value out of your PEX lines, you need to plan differently for a PEX installation. Instead of following a roadlike network of large pipes that would normally feed smaller ones in straight-line fashion, water flows from the main PEX line to a central location called a manifold, which in turn feeds smaller PEX lines (similar to the arms of an octopus) that supply fixtures directly.
This configuration delivers consistent pressure to all PEX-connected fixtures, because it creates a hub where water is equally directed to various points in the house. The line supplying your manifold should be three-fourths inch in diameter, with half-inch-diameter branch lines sprouting off from the manifold.
To connect separate pieces of PEX to valves, manifolds and joints, you have a choice between compression fittings and crimp-on rings. Compression fittings connect with threaded parts you tighten together. For small jobs involving less than 20 joints, compression fittings are the most cost-effective option for PEX. To attach a compression fitting, just slip a nut onto the PEX, push the cut end of PEX line over the O-ring on the end of the fitting and tighten the nut with a couple of wrenches (see Nine Types of Wrenches and Pliers).
Compression fittings are faster, easier and safer to install than any solder joint, but the drawback is they are relatively expensive. For smaller jobs, you can justifiably spend $5 or more on a threaded elbow, a connector or a T-shaped compression fitting. But for bigger jobs that require many fittings, the cost will add up.
Professional plumbers almost always prefer crimp-on connection rings because they’re less expensive, and they install faster and easier than wrench-tightened compression fittings — but there’s a catch. Crimping tools can cost several hundred dollars each, and you’ll need one tool for half-inch joints and yet another for three-fourth-inch joints. The price of these tools is justifiable only if you are plumbing more than one building. Crimping tools are durable, which makes them good candidates for a shared purchase among several neighbors. Keep them oiled and indoors, and they’ll last forever.
The crimping rings themselves are simple, inexpensive metal bands that work great. Just slip one onto the PEX, assemble the joint, slide the ring over the joint, open the jaws of your crimping tool over the ring, then squeeze the jaws shut. The force of the crimping tool makes the diameter of the ring slightly smaller, resulting in a tight and permanent joint. But before you use the tool, make sure you’ve got the joint positioned where you want it. The only way you can pull the joint apart later is by cutting off the crimped ring with a hacksaw and prying it off the PEX line.
Before you buy PEX and plumbing supplies, create a schematic drawing of your proposed layout. Mark the location and type of any fittings you will need, and note any major obstacles caused by framing details or inconvenient routes. By doing this, you can make a list of all the supplies and tools you will need before making a trip to the hardware store. As you plan your layout, remember that the flexibility of PEX offers potential for designs not possible with rigid piping. For instance, you can run PEX lines through holes drilled in floor joists, keeping your pipes tucked up inside the floor frame, where they will be out of the way.
After you’ve planned your layout, bending and positioning your PEX is easy. But before the job is done, you’ll also need to cut, ream and install joints in PEX; drill holes in wood and drywall; and connect hoses to fixtures.
Boring holes. To drill holes through walls, joists or drywall, use a 1-inch-diameter self-feeding auger for half-inch water lines, and a 1 1/4-inch auger for three-fourths-inch lines. Ample clearance reduces installation friction when you pull the PEX lines through the holes. Putting in PEX lines this way is much like pulling heavy electrical cable, so recruit someone to help you. Have your helper unroll 10 or 12 feet of PEX from the coil, then pull it into place before unrolling more.
When installing PEX in floor joists, the only difficulty you’ll likely encounter is boring all those holes in tight quarters. To drill these holes, your best option is a cordless right-angle drill with a short self-feeding auger bit. To align your cuts, follow the joint lines of the plywood subfloor, or snap a chalk line along the bottom edges of the joists. The more uniform the hole location from joist to joist, the easier it will be to pull the PEX lines into place.
Cutting. You can cut PEX with specially designed, inexpensive shears that have a single metal blade. The trick to cutting PEX with this tool is making a two-step slice: With the first stroke, cut most of the way through the tube, rotate the shears a quarter-turn, and then finish with another squeeze. Whatever you do, don’t struggle using a hacksaw or copper pipe cutter — neither cuts PEX very well.
Reaming. The pressure required to cut PEX doesn’t flatten the pipe completely, but it does create an oval profile that you need to correct. That’s why the next step in completing a joint involves widening the opening of the PEX line with a simple tool. The reaming tool does two things: It imparts a perfectly round shape to the inside of the pipe, while also chamfering (beveling) the inside edges of the opening to prevent damage to the O-rings that seal the fittings after assembly. Cutting and reaming each joint takes just seconds, but be sure you ream carefully and evenly. The inside edge of the PEX line end must be a smooth, beveled surface. If you leave behind a sharp edge or a stray piece of plastic, the all-important O-rings in the joint can become damaged and cause a leak.
Installing valves. When you install any new plumbing, you should test the system for leaks before hiding the pipes behind drywall or paneling. That’s why it’s a good idea as you work to install shut-off valves at the end of each run of PEX. Later, you’ll need the valves to shut off the water during fixture maintenance, but the valves also serve a useful and immediate purpose. You can turn on the main water supply valve and then bleed off air using each individual shut-off valve. This lets you look for water leaks that probably wouldn’t be visible if small amounts of air were leaking out of the pipe. Even if you forget to tighten or crimp a joint connection, the O-rings alone will often prevent leakage in PEX installations, at least temporarily. You should double-check that each joint is tight, even if the connection appears leak-free after you bleed off the trapped air.
If you’re plumbing a seasonal home and you plan to drain the system each fall, then install your PEX water lines on a slight slope toward a drain valve in a convenient location that will allow the water to run out. This way, you can easily drain water when you expect freezing conditions. Don’t guesstimate the slope, either. Measure, snap a chalk line and then bore holes to make an evenly tilted line through building frame members. Dips in the slope will result in PEX with left-behind pockets of water, which could result in cracking after numerous winter freezes.
Connecting to fixtures. Eventually, all your lines of PEX will connect to fixtures, faucets and water bowls that supply your house, barn and outbuildings. These fixtures are not made to accept PEX lines directly, so you’ll need to add transitions. The best way is to install a shut-off valve with a threaded end that’s designed to accept a flexible, reinforced supply line. Supply lines range in length from 8 to 24 inches and are made from neoprene, reinforced with a mesh of braided stainless steel that’s wrapped around the outside to increase the resistance to water pressure inside the line. Place the ends of each PEX line 8 to 12 inches away from where you think the connection point for your fixtures should be located. The braided flex line will get you the rest of the way without hassles.
The do-it-yourself advantages of PEX piping are a clear indication that wisely chosen newer building materials can be a big help for people with a heart for self-reliance. All that’s required is a bit of knowledge about the materials and methods of building, faith in ourselves and initiative to get the job done.
You will need a special fitting when connecting PEX lines to existing copper supply pipes. One end of this fitting is soldered into either half- or three-fourths-inch copper, and the other end includes O-rings and a profile that accepts a PEX line.
The O-rings must be removed before you solder the fitting. To remove the soft O-rings, squeeze them with two fingers to create a bulge in the rubber that you can grab with your other hand. (The O-rings can become damaged if you try to grip them with pliers or a screwdriver.) After the O-rings have been removed, clean the copper joint with sandpaper, brush on a coat of soldering flux, heat it up and then apply solder. Only when the metal is completely cool can you safely reinstall the O-rings and complete the joint.
Contributing Editor Steve Maxwell has been helping people renovate, build and maintain their homes for more than two decades. “Canada’s Handiest Man” is an award-winning home improvement authority and woodworking expert. Contact him by visiting his website and the blog, Maxwell’s House. You also can follow him on Twitter, like him on Facebook and find him on Google+.