Technical Blog

Welcome to John’s Blog. Answers to frequently asked questions are periodically posted here. The objective is to share information about PVC pipe with readers as well as with utilities, design engineers and pipe installers. The blog provides the latest information on PVC pipe design, installation, and application for water and wastewater infrastructure projects.

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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.

Ductile Iron Pipe’s Hazen-Williams Flow Coefficient Declines Over Time

Posted By John Houle on Jan 23, 2018

The Ductile Iron Pipe Research Association (DIPRA) states that ductile iron (DI) pipe does not experience a decline in hydraulic performance over time. However, the very document that makes this statement is full of data that contradicts the claim.

In addition to DIPRA’s own data, there are many other studies that confirm that DI pipe’s Hazen-Williams “C” coefficient decreases as the pipe ages. 

This concept is very important in analyzing pumping costs and greenhouse gas emissions over the life of a DI pipeline. The use of an unrealistically high “C” factor provides a misleading scenario that unfairly favors DI pipe over its competitors.

For the Tech Brief on the decline in DI “C” over time, click here.