How the Logic Approach to Plumbing With PEX Can Help Your Business

If you’re using PEX pipe, consider installing it using the Logic method, which offers several benefits over home-run and trunk-and-branch layouts

How the Logic Approach to Plumbing With PEX Can Help Your Business

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Plumbers who have been in the residential building industry for the past decade or more have most likely heard of PEX. And with the launch of larger pipe sizes over the past few years, the commercial industry is also noticing the benefits of PEX as well.

However, just when you think you have this PEX stuff all figured out, a better way to plumb with the pipe material comes along. And you’ll want to take notice because this better way to plumb with PEX will benefit you in a number of ways — even faster installs, fewer materials and less opportunity for leaks than ever before.

Logic plumbing defined

The Logic approach maximizes the flexibility of PEX pipe to reduce connections and potential leak points, while also incorporating multiport tees located near fixture groupings to limit the amount of pipe and number of connections needed and improve installation efficiencies.

This installation method uses considerably less pipe than a home-run layout, with only a few more connections, and it requires significantly fewer connections compared to a trunk-and-branch installation.

At the heart of a Logic design is the multiport tee. It is a long tee with multiple outlets, but it’s not considered a manifold, so you don’t need to worry about access behind a wall. The multiport tee greatly reduces connection points due to its ingenious design. For example, six regular tees require 18 connections, but a flow-through multiport tee with six outlets needs only eight connections: six connections for the ports, a main flow-through inlet, and a main flow-through outlet.

With a multiport tee, you’re still able to have six plumbing lines going out from the main line, but you now have fewer than half the number of connections. Think about how much faster you could complete an installation with half the number of connections.

Additionally, multiport tees require less space to install. With six regular tees, you’d need about three times more space to install all six tees. Compare that to installing one, compact multiport tee with six outlets.

If you’ve never heard of multiport tees, here’s a quick rundown: They are made of engineered polymer (EP), a thermoplastic material that has superior mechanical, chemical and thermal properties that provide dimensional stability in demanding applications, including areas of high stress, heat and moisture.

EP has been successfully used in plumbing applications for more than 20 years, and it’s the same durable, reliable material that’s been used in the medical appliance and aerospace industries for even longer. In fact, strength tests show an EP tee can withstand up to 4,000 pounds of spreading force without failure. There’s no concern about its strength and durability.

And, just like PEX, the EP material in multiport tees resists corrosion, pitting and scaling, so it creates a highly durable system that’s engineered to last. Best of all, multiport tees (as well as all EP fittings) are approved for direct burial in the soil or concrete slab, so they are ideal for in-slab plumbing applications as well.

The Logic layout

How does a Logic layout actually work? The Logic design uses a main line going to a multiport tee, with distribution lines going out from that tee. These individual lines extending from the single multiport tee provide water to all fixtures in a single or adjacent grouping.

Here’s where the Logic design makes more sense than home-run and trunk-and-branch layouts. Take a 2,300-square-foot, two-story home, for example. A Logic design requires only 637 feet of pipe, while a home-run system uses 1,515 feet of pipe. In addition to the added costs required for more product and the time it takes to install that additional product, all the extra pipe can lead to issues isolating hot- and cold-water lines. This increases heat transfer and energy inefficiencies within the plumbing system. Additional pipe can also mean reduced water pressure and longer wait times for hot water to arrive at the fixture. A Logic layout provides faster hot-water delivery and reduced pressure loss for a higher-performing system.

While it’s true a Logic installation uses slightly more connections than a home-run layout (59 vs. 48 in the 2,300-square-foot, two-story home example), the amount of pipe savings is significantly more beneficial. If you’re using a reliable fitting system, such as an ASTM F1960 expansion fitting system, you can have even greater confidence with the only PEX connection method that actually gets stronger over time.

Speaking of connections, if you really want to limit those, Logic is the way to go over a trunk-and-branch system. Again, using the two-story home example, a Logic layout would use a mere 16 fittings and 59 connections compared to 96 fittings and 165 connections for a trunk-and-branch layout. These added connections add significant time to your installs and increase your potential for leaks. Plus, they greatly limit system performance with increased pressure loss. 

To sum it up: Get faster installs, reduce the opportunity for leaks, and increase system performance with a Logic layout.

A final thought

One more important point to note about the benefits of multiport tees: They can offer significant advantages for clustered or consecutive uses of hot water. Once hot water arrives at a multiport tee, it is readily available to all fixtures connected to that tee. Essentially, that multiport tee's fixture grouping is “charged” with hot water.

For home-run systems, hot water is not necessarily readily available for clustered uses that occur at faucets other than the original (first-use) fixture. The hot water is available only at the central manifold. The system must still deliver hot water all the way from the manifold to the faucets where subsequent clustered uses are taking place.

Using multiport tees is also advantageous for hot-water recirculation systems, because it’s easy to install recirculation “loops” that return water to the heater. This is not as easy with a home-run configuration where recirculation can typically be done only between the central manifold and the water heater, but not between the fixtures and the water heater (because it would be necessary to recirculate from each fixture).

From fewer connections to faster installations to greater performance, you can see why it makes sense to install a PEX plumbing system with a Logic design. 

To learn more about Logic plumbing, visit

To learn more about PEX pipe in general, visit or

About the Author

Kim Bliss is the content development manager at Uponor. She can be reached at


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