THE RISING COST OF COPPER has boosted the appeal of plastic piping alternatives such as cross-linked polyethylene (PEX) among builders. In a field study of copper and PEX water supply systems, the NAHB Research Center and the Partnership for Advancing Technology in Housing (PATH) partnered with builder Fernando Pages to provide a definitive comparison of the installation time, material cost, and performance of each in single-family homes.

Testing began in June 2005 at Liberty Village, an urban infill community developed by Pages' Lincoln, Neb., company, Brighton Construction. Four test homes shared the same architectural plan: 1,500 square feet, with two full baths on the second floor; a kitchen sink, powder room, and two hose bibs on the first floor; and washer hookups in the basement. The plumbing systems were installed by the same general contractor, who had experience in both PEX and copper. In two homes, a traditional trunk-and-branch system was used with ½-inch and ¾-inch copper; in the other two homes, a home-run system with ¾-inch, ½-inch, and 3/8-inch PEX was used.

A time-in-motion study was conducted to assess the time required for various tasks associated with each system. PEX's home-run system of flexible sweeps and limited joints offered significant installation time savings over copper, which required additional man-hours for fittings to be sweated. Since both systems had comparable flow rates, performance results were marked by PEX's faster hot water delivery—an average of 30 percent for the lavatory farthest from the hot water heater. Comparisons of material costs at the time of the study (the first quarter of 2006) showed that copper was somewhat less expensive, primarily because of the added cost of the central manifold for PEX and the limited availability of PEX materials in the local plumbing supply. Overall, installation and material costs for PEX were 28 percent less than for copper, on average, in identical houses.

The final report detailing field results, costs, and all time-in-motion factors is now available. For the full report, visit