Technical Blog

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John Houle: Senior Technical Consultant, PVC Pipe Industry

John Houle holds a Master’s Degree in Civil Engineering from the University of Missouri and an MBA from the University of Oregon. He has more than 25 years of experience in the plastic pipe industry in applications engineering, market development, forensic analysis, technical writing, and standards development.

Dimension Ratio (DR) Explained

Posted By John Houle on May 23, 2013

The PVC pipe industry sometimes makes use of technical abbreviations that may not be fully understood by utility and consulting engineers. “DR” is a case in point.

Mathematically the idea is simple, but the reasons for its use are not always obvious. Further, the interchangeable use of DR and SDR (Standard Dimension Ratio) can also add a layer of confusion.

The attached technical brief discusses the math, distinguishes between DR and SDR, and provides the rationale for the concept’s use for both PVC pressure and non-pressure pipe.

Click here to read.

A numerical example will illustrate the idea – below are dimensions for three sizes of DR18 PC235 pressure pipe:

Size
(in)

Outside Diameter
(in)
Minimum Wall
(in)
DR
6 6.900 0.383 18
12 13.200 0.733 18
24 25.800 1.433 18


As OD increases, the wall increases proportionally so the dimension ratio of 18 is maintained.