Why You Should Consider Logic Plumbing with PEX

PEX in the ceiling | Construction Pro Tips

How Logic Plumbing with PEX Beats Home Run and Trunk and Branch

By Kim Bliss

 If you’ve been in the residential plumbing business for the past decade, you’ve most likely heard about PEX pipe. It’s a flexible, durable, plastic piping material that’s now used in more new-home construction than copper and CPVC combined.

However, you may not know there’s a new (and smarter) way to design and install a residential PEX plumbing system that goes in faster, uses less materials, minimizes liability and operates more efficiently.

While trunk-and-branch and home-run systems have been the staple for plumbing designs in the past, the better way to plumb a home is with a Logic layout. 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 both limit the amount of pipe and connections needed while also improving installation efficiencies and system performance.

A Multiport Tee | Construction Pro Tips

What’s a multiport tee?

I’m sure right now you’re wondering, “What’s a multiport tee?” It’s essentially a bunch of tees all molded together to create one long tee with multiple outlets. This innovative product minimizes connections and is the heart and soul of a Logic design.

For example, six regular tees will have 18 connections, but a flow-through multiport tee with six outlets will only have eight connections (six connections for the ports, a main flow-through inlet and a main flow-through outlet). Think about how much faster you could install a system when you’re making half the number of connections.

Plus, multiport tees require less space to install. If you’re installing six regular tees, you’d need about three times more space to install all six tees compared to installing one, compact multiport tee with six outlets.

And get this — while multiport tees may resemble a manifold, mulitport tees have the benefit of being hidden behind walls without the need for an access panel. Yes, you heard that right. No need for an access panel, minimizing costs and labor to help keep your projects on schedule and on budget.

Multiport tees have been used in residential (and even commercial) plumbing systems for more than a decade. 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 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.

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.

A PEX Pipe Layout | Construction Pro Tips

The Logic layout

So what exactly is a Logic plumbing layout? A Logic layout features a main line going to a multiport tee with distribution lines going out from the tee. These individual lines extending from the single multiport tee provide water to all fixtures in a single or adjacent grouping.

This design uses significantly less pipe than a home-run layout, with just a few more connections. And it requires significantly fewer connections compared to 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. That’s more than twice the amount of piping necessary.

Why is this a problem? 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.

Plus, additional pipe can 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.

I will note that 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 above), the amount of pipe savings is significantly more beneficial to the efficiency of the system. And if you’re using a reliable fitting system, such as an expansion fitting system, you can be assured a leak-resistant installation that reduces your liability.

Speaking of connections, if you really want to limit your liability, Logic is the way to go over a trunk-and-branch system. With the two-story home example above, a Logic layout uses a mere 16 fittings and 59 connections compared to a whopping 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!

These added connections greatly limit the performance of the system with increased pressure loss and also significantly increase the potential for leak points. In short, limit your liability and increase the performance of your plumbing systems with a Logic layout.

Hot Water System Diagram from PEX | Construction Pro Tips

Hot-water delivery benefits

One more important point to note. Multiport tees can also offer significant advantages for clustered or consecutive uses of hot water as well. 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.

In a home-run configuration, however, hot water is not necessarily readily available for clustered uses that occur at faucets other than the original (first-use) fixture. 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 only be done 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).

So there you have it! Just a few “logical” reasons why you should consider a smarter approach to plumbing a home that will improve your installation times, limit your liability and offer an all-around better-performing system for the end user.

Kim Bliss is the Content Development Manager for Uponor North America