Fixture Flow Rate Comparison - Cross-Linked Polyethylene (PEX) Piping and Copper Tubing

Published Monday, June 30, 2008

Cross-linked polyethylene (PEX) and copper piping were tested at varying source pressures and two maximum runs; 60 and 100 ft to determine if PEX and copper piping systems will deliver sufficient volumetric flow rates to the plumbing fixtures when using the same nominal size tubing.

This testing used the same PEX trunk and branch system as research conducted in November, 2006 (see Residential PEX Water Supply Plumbing Systems: Design Guide, 2006). A copper pipe system was developed and both went through the same test procedures. One fixture, the primary Test Fixture, was monitored during each flow sequence. This Test Fixture was located the farthest from the source supply, both in distance and elevation. The flow rate and pressure at this fixture provided the basis for analyzing the performance data of each system design and with multiple fixtures operating simultaneously.

This research determined that in a typical single-family residential plumbing system, PEX and copper piping systems will deliver sufficient volumetric flow rates to standard residential plumbing fixtures when using the same nominal size tubing. While PEX tubing has a smaller inside diameter than copper tubing, at a given source pressure, both tubing systems meet the farthest fixture demand. This is the case even with multiple fixtures flowing. 

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