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.
PVC and fiberglass (FRP) compete in the 24- to 60-inch sewer pipe market. However, FRP is much more sensitive to pipe deflection (ovalization) under earth and traffic loads, but you would never believe it from their literature. For example, the entire flexible pipe industry uses “PS” as an abbreviation for pipe stiffness. Not FRP — they use “SN” to signify stiffness number. Although pipe stiffness is pipe stiffness no matter what abbreviation you stick in front of it, FRP contends that (somehow) the letters “SN” make their stiffness stiffer. Of course, this is quite silly. The PVC Pipe Association has just published a document that goes behind the curtain and exposes FRP as a product that does not respond well to deflection when buried. Not only are the PS and SN numbers proven to be equal, but FRP is shown to crack at small deflections that are very safe for PVC. Engineers and owners should consider controlling the deflection of FRP for their projects. Flexible pipe design demonstrates there is never a need to specify a higher stiffness for PVC than for FRP. In most cases, FRP should be specified in higher stiffnesses than PVC. The technical paper includes a review of failed FRP projects that imposed millions of dollars of repair costs on utilities. The paper is worth a thorough read. Check it out by clicking here.
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