How to Pipe an Entire Home With PEX

Plumbing, fire sprinkler systems and radiant floor heating are all viable uses for PEX pipe

How to Pipe an Entire Home With PEX

A sprinkler installation using PEX pipe.

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Among the benefits of PEX pipe is its versatility. It can effectively be used in all parts of a home — plumbing, fire sprinkler systems and radiant floor heating.

Here’s a closer look.

Plumbing with PEX

There’s a reason many contractors are installing PEX over copper or CPVC. It’s flexible, allowing for fewer connections and faster installs. Plus, it doesn’t have scrap value or price fluctuations like copper, so it’s easier to bid jobs. Nor do you have to worry about your valuable product walking off the job site.

Making connections with PEX is much easier without the need for flame or messy glues. You can use the professionals’ expansion method that uses an expansion ring and an expansion tool. Or you can use crimp, clamp, push-to-connect or expansion/compression systems. For more information about the different PEX connection methods, check out my previous article "Making a Connection: A Comprehensive Guide to Putting Together PEX Pipe."

There is also now a new, smarter way to install a PEX system that goes in faster, uses fewer materials, requires fewer connections and minimizes your liability: Logic Plumbing.

The Logic approach leverages the flexibility of PEX pipe to minimize connections and reduce potential leak points, while also incorporating multiport tees located near fixture groupings to limit the feet of pipe and the number of connections needed.

A multiport tee is essentially a bunch of tees molded together to create one long tee with multiple outlets. For example, six regular tees have 18 connections, but a flow-through multiport tee with six outlets has only eight connections. Think about how much faster you could install a system when you’re making half the number of connections.

For a Logic layout, a main line connects to a multiport tee, with individual distribution lines going out from the tee. These distribution lines provide water to all fixtures in a single grouping or adjacent groupings.

This Logic design uses significantly less pipe than a home-run layout, with just a few more connections. Plus, it requires considerably fewer connections compared with a trunk-and-branch installation.

For example, a 2,300-square-foot, two-story home using a Logic design requires only 637 feet of pipe while a home-run system uses 1,515 feet of pipe. While it’s true a Logic installation uses slightly more connections than a home-run layout (59 versus 48 in the 2,300-square-foot, two-story home example), the savings in pipe feet is significantly more beneficial in terms of labor as well as material savings.

A Logic layout also installs much faster compared with a trunk-and-branch system, due to the dramatic reduction in connections. With the two-story home example, a Logic layout uses a mere 16 fittings and 59 connections compared with 96 fittings and 165 connections for trunk-and-branch. That’s six times the number of fittings and nearly three times the amount of connections.

The next time you’re planning a job, give Logic Plumbing with PEX a shot. You won’t be disappointed.

PEX multipurpose fire sprinkler systems

First introduced in the mid-1990s, multipurpose PEX plumbing and fire sprinkler systems were a revolutionary idea — combining the cold-water plumbing and the fire sprinklers into a single system. With this new concept, professional plumbers were able to add a new and profitable service to their offerings, while helping homebuilders meet the ever-expanding sprinkler mandates across the country.

Adding fire sprinklers to a home’s cold-water plumbing is remarkably easy. The sprinkler is essentially just another fixture to tie into the plumbing line. This is a slam-dunk for most plumbers, who already install PEX plumbing systems and have the tools, knowledge and — most importantly — relationships with builders.

Depending on the jurisdiction, multipurpose systems typically do not need check valves or backflow preventers. In addition, because they are part of the potable plumbing system, they don’t use antifreeze. In short, all those added costs are eliminated.

As long as you’re a licensed plumber, you can install these multipurpose systems in most jurisdictions. Training typically involves online or classroom work along with a day or two on the job site. Before you know it, you’re offering your builders a solution to meet the fire sprinkler mandate and making more money on every home.

Where do you start? First, you need a quality design. Some PEX manufacturers offer design services, so you can have your system designed by a NICET-certified professional whose work meets the NFPA 13D standard for the installation of residential sprinkler systems. (Send me an email at kim.bliss@uponor.com, and I can hook you up.)

If you want to learn more about residential PEX multipurpose plumbing and fire sprinkler systems, check out information on various fire protection association websites, such as nfpa.org or nfsa.org.

A radiant system install using PEX pipe.
A radiant system install using PEX pipe.

PEX hydronic radiant floor heating

If you are interested in getting into radiant heating, know that there’s a lot to learn. Starting with a proper design is key. If your design is wrong, there’s nothing you can do to fix the system once it’s installed. If you need guidance with a design, once again many PEX manufacturers offer radiant design services to guide you through the process.

Once you have a design that has incorporated the proper heat-loss calculations, flooring R-values, room sizes, etc., you can move on to installation.

When it comes to installing PEX piping for a hydronic radiant system, there are a few basics to learn regarding on-center spacing, pipe sizing and loop lengths.

On-center spacing: When laying out the piping on the floor for a radiant heating system, it’s important to maintain the correct on-center spacing to ensure even heat throughout the space. Typical spacing for interior radiant floor heating applications is 6 inches or 9 inches on center. 

However, it’s not always necessary to have even spacing in a layout. For example, some interior radiant floor heating designs use 6-inch spacing for the first few feet along perimeter walls and then increase to 8-, 9- or even 12-inch spacing in the middle of the room. In general, the tighter the spacing, the lower the water temperature required to supply heat to the floor. Lower water temperatures also reduce the risk of striping across the floor, providing a more even surface temperature.

Pipe sizing: Don’t assume a larger pipe size means more heat. While larger pipe allows for greater flow, the diameter has more impact on the loop length than on the BTU delivery. Selecting the proper heat source and calculating the Delta T in the design will ensure the right amount of heat is entering the conditioned space.

Loop lengths: As noted, pipe diameter dictates the maximum loop length. Smaller pipe produces greater pressure loss than larger pipe, so shorter loop lengths are recommended for smaller pipe sizes. For example, use 1/2-inch pipe for 250- to 300-foot loops, 5/8-inch pipe for 350- to 400-foot loops, and 3/4-inch pipe for 500-foot loops.

One last important note: Be sure to use a PEX pipe with an oxygen barrier. All plastic pipe is vulnerable to oxygen molecules permeating its walls, and oxygen wreaks havoc on the ferrous components in a hydronic radiant heating system, causing them to rust. Ensure the PEX pipe you use features a factory-applied oxygen-barrier coating during the manufacturing process to keep the oxygen out and your system safe.

To learn more about hydronic radiant floor heating systems, visit radiantprofessionalsalliance.orghealthyheating.com or heatinghelp.com.

About the Author

Kim Bliss is the content development manager at Uponor. She can be reached at kim.bliss@uponor.com.



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