Work More Productively and Profitably With Polymer Piping Systems

Materials like PEX and PP-RCT — either on their own or in a hybrid system — provide numerous advantages for plumbing and mechanical piping systems

Work More Productively and Profitably With Polymer Piping Systems

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One major way the plumbing industry is advocating for the trades and, in turn, seeing positive results in the areas of job site safety, productivity, efficiency, and profitability is through the design and installation of polymer piping systems, such as PEX and PP-RCT.

PEX, or crosslinked polyethylene, began being used in North America in the mid-1980s. It started with radiant floor heating systems, then moved into plumbing and, eventually, to hydronic hot-water heating and chilled-water applications.

PP-RCT, which is an acronym for polypropylene, random copolymer with crystallinity and temperature resistance, is the newest generation of high-performance polypropylene resins. Introduced in North America in the late 2000s, PP-RCT is manufactured through a special process that modifies the crystalline structure, resulting in a material with greatly improved temperature and pressure resistance that allows it to remain ductile throughout its service life for long-term, superior performance.

Quick Facts

PEX can be manufactured via three different processes. This creates pipe with various crosslinking percentages that allow for different characteristics. PEX-a is the most durable, flexible, and resilient with crosslinking around 85%. PEX-b is a stiffer piping product with crosslinking around 65% to 70%, and PEX-c features crosslinking around 70% to 75%.

PEX-a is the most flexible of all the PEX types. It features a bend radius of six times the pipe’s outside diameter, and it can expand up to three times its size and then contract back down, making it much more resilient in freezing conditions. 

PEX is available in pipe sizes from 1/4-inch to 3-inch for potable systems and 5/16-inch to 4-inch for mechanical systems. It also features a standard dimension ratio (SDR) of 9. For those unfamiliar with SDR, it is the method for rating a pipe’s durability against pressure. Literally, it is the ratio of the pipe’s outside diameter to its wall thickness.

Connection methods for PEX include crimp, clamp, compression, and expansion. However, most professionals use the ASTM F1960 expansion method because it can never be dry fit and allows a larger-internal-diameter fitting for better system flow and performance. Note that ASTM F1960 connections are mainly used with PEX-a pipe since expanding PEX-b or PEX-c pipe can create microcracks in the pipe.

For PP-RCT, the pipe is available in a variety of sizes and SDRs. Depending on the manufacturer, pipe sizes can range from 1/2-inch all the way up to 24-inch with SDRs of 7.4, 9, 11, and 17.6. For pipe sizes 4 inches and smaller, the primary connection method is socket fusion fittings. For sizes 6 inches and larger, there are fabricated butt fusion fittings.

Some manufacturers also offer a mechanical pipe with a co-extruded middle fiber composite layer that helps to reduce linear expansion. This middle fiber layer allows expansion rates similar to metal piping systems. It also enables further spacing with hangers due to the added strength the fiber layer provides.

Key Benefits

PEX and PP-RCT have similar benefits that make them ideal for greater job site safety, productivity, efficiencies, and profitability potential. They’re also an excellent match for use in a hybrid piping system.

Both piping systems are much lighter in weight compared to metals — up to 80% lighter than copper or steel — which can have a significant impact on job site safety, material handling labor, and even hanger types.

They will not corrode, rust, or scale, so they can last for decades. Also, from a design standpoint, there is no need to upsize the system on the front end to account for scale buildup.

For connections, both the PEX ASTM F1960 expansion method and the PP-RCT fusion method can never be dry fit, eliminating any concerns if a fitting was completed. Also, neither system requires open-flame welding or soldering, making job sites safer and eliminating the need for fire watch.

The flexibility of PEX eliminates the need for many connections with each change in direction. This saves installation time, minimizes product and labor costs, and makes it much easier for new tradespeople to learn the job.

Both piping products offer relatively stable pricing and do not experience the daily price fluctuations of commodity metals, making the systems easier to bid.

They can be more environmentally friendly. The long coils of PEX help reduce job site waste, and the durability of the system eliminates the need for re-piping every 10 or 20 years like some metal systems. Additionally, the process of mining metals from the earth causes many problems for the environment and damages ecosystems important to the animal and human life in the area as well as land degradation, deforestation, ground and surface water pollution, and habitat destruction. 

The Ideal Piping Solution

It’s easy to see how PEX and PP-RCT — either on their own or in a hybrid system — provide numerous advantages for plumbing and mechanical piping systems.

With the industry always in need of newer, more innovative solutions for designing and building structures, it’s a smart idea to consider polymer piping systems where they make sense and take advantage of all the benefits they provide.

It can help construction businesses grow and thrive while making job sites safer and more productive and also create buildings that are more sustainable for decades to come.

About the Author

Kim Bliss is the technical and marketing content manager at Uponor. She can be reached at


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