Using PEX to Maximize the Benefits of Hybrid Piping Systems

Varying pipe materials within a single system can help you tap into the best characteristics of each type of pipe

Hybrid piping systems are becoming more popular with the need for value engineering to meet budgets and tight production schedules. What was once a one-piping-material project for domestic water or mechanical hydronic systems has turned into a multipipe opportunity.

I say “opportunity” because having multiple piping systems in a project can often maximize the best characteristics of each pipe type. For example, what works best for risers and mains might not work best for in-suite piping. Some pipe materials have greater benefits the larger they get. Others have more benefits in smaller sizes.

We are fortunate these days to have many piping options for plumbing and mechanical systems, including copper, CPVC, steel, black-iron pipe (BIP), polypropylene (PP-R or PP-RCT) and crosslinked polyethylene (PEX). You can take the best benefits of these pipe types and create a high-performing, reliable and — best of all — more profitable system when you have the option to go hybrid.

Why PEX is ideal for hybrids

With its flexibility, durability, long coil lengths and lighter weight, PEX is an easy-to-install piping system for risers, distribution piping and in-suite applications. It even works great in direct-burial applications for underground plumbing. It resists corrosion, pitting and scaling, and features a unique shape memory that allows it to expand and retract back to its original size, making it highly resistant to freeze damage.

PEX is approved in most jurisdictions around the country for installation in both residential and commercial applications. Plus, it can use various connection methods that are all relatively easy to learn and quick to install. These include: crimp, clamp, push-to-connect, expansion, and expansion with compression.

Since PEX is currently available only in sizes up to 3 inches for domestic-water applications and 4 inches for mechanical hydronic applications, it’s a good candidate for hybrid systems that require larger piping sizes. PEX can connect to copper, CPVC, steel, BIP and polypropylene. Some manufacturers offer a comprehensive offering of transitions to make the connection between these piping systems.

Cold-expansion transition adapters

Obviously, you can’t do the job if you don’t have the right parts. Thankfully, there are numerous ASTM F1960 cold-expansion transitions available on the market: 

• Brass transition adapters, in sizes from 1/2 inch to 3 inches for plumbing and mechanical applications, can connect PEX to male thread, female thread, copper tubing sweat, copper fitting sweat and copper fitting press.

• CPVC spigot and socket adapters connect ASTM F1960 transitions.

• Roll-groove fitting adapters offer a direct copper tube size or iron pipe size connection, transitioning from PEX to metal pipe for domestic water, hydronic hot-water heating or chilled-water cooling pre-fabrication opportunities.

Importance of building information modeling

When designing a hybrid PEX piping system, incorporating building information modeling makes a significant difference in the installation’s efficiency. It’s important to set up templates and preferences for PEX that relate to the unique installation characteristics of the pipe.

For example, manufacturer-provided PEX content ensures the system takes advantage of the unique features of PEX, such as the flexibility of the product. This same content also takes into consideration the challenges, such as expansion and contraction of the pipe. Take smaller-dimension PEX. The system knows to create a bend in the pipe with a change in direction, rather than using an elbow.

PEX content can be accessed either from the manufacturer’s website or through third-party websites and add-ons. However, it is best to go with the content directly from the manufacturer since those databases will most likely have the most accurate and reliable content.

A final word

I often end my articles about PEX by stressing the importance of sticking with one brand on a project. That’s because certain PEX pipes and fittings are designed and manufactured to work together for the strongest performance.

Using one brand of pipe and another brand of fitting can potentially compromise the installation and system performance. This may also limit the warranty, potentially leaving the liability on the contractor. Protect your reputation and sleep well at night knowing the system you’re installing is covered by a full warranty and customer support.