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.

If you are interested in having the response to your question considered for posting, e-mail John at techblog@uni-bell.org

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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.



New C900 Standard for PVC Pipe

In August 2016, AWWA published the latest edition of its C900 standard. C900-16 is more complicated than most standards, primarily because it now includes the large-diameter sizes previously found in the C905 standard.


John Houle

AWWA PVC Pipe Standards Over the Years

AWWA has recently published the sixth edition of its C900 standard for PVC pipe. This Tech Brief looks at milestones in the progression of the C900 and C905 standards, culminating in the combining of the two standards into AWWA C900-16.


John Houle

Today's Thinner-Walled Iron Pipe - More Susceptible to Corrosion

The iron pipe industry likes to brag about pipe that has been in service for a long time – some for more than 100 years. However, it’s important to put this into proper context.


John Houle

Q & A on Max Test Pressure of Installed PVC Pressure Pipe

Question – one question that I hear quite often about testing of installed PVC pressure pipe is: “What is the maximum test pressure I can use?” Answer – since every component of a pressure pipeline has a pressure rating, the simple reply is: Do not exceed the pressure rating of any of the pipeline components.


John Houle

PVC Pipe Cyclic Design - AWWA

AWWA first included cyclic design for PVC pipe in the 2007 edition of the C900 standard. The same method was later incorporated into the C905-2010 and the C900-16 standards.


John Houle

Biased Results in Study on Water Pipe Materials

In July 2016 a study was published titled “A Framework to Evaluate the Life Cycle Costs and Environmental Impacts of Water Pipelines.” The study, funded by the Ductile Iron Pipe Association (DIPRA), “aims to develop a Pipe Material Life Cycle Assessment tool (PMLCA) that is capable of analyzing different pipe material scenarios and suggesting the best option to the various decision makers.”


John Houle

Manning's "n" for PVC Gravity Sewer Pipe

“Conservative” design is taught continually to all engineers during college and throughout their employment. I think we can all agree that this is a good idea – we don’t want engineers to cut corners and cause potential problems.


John Houle

PVC Pipe Bell Direction

Questions sometimes arise about which way the bell should be positioned in a PVC pipeline. Typically there are two concerns: 1. Does bell direction make a difference in pipeline hydraulics? 2. Does it make a difference during installation?


John Houle

PVC Pipe Joints - Trenchless Options

In trenchless installations, pipes are typically pushed or pulled into position. This pushing or pulling causes loads on the pipes that are not encountered during open-cut construction. As a result, the PVC pipe industry has developed four types of restrained-joint systems for trenchless projects.


John Houle

Safety Considerations for Air-Testing of PVC Sewer Pipes

Occasionally I hear a report about safety issues with air-testing of sewer pipes. The story usually starts with “An end-plug let go.” There was a sudden whoosh of air out of the manhole that had potential consequences for nearby personnel.


John Houle

An Engineering Primer on AWWA C900/C905 PVC Pipe

Engineers who are unfamiliar with PVC pressure pipe sometimes have a list of questions about the product. These questions, which often arise from misinformation propagated by competitive materials, usually have logical answers based on engineering principles.


John Houle

New PVC Pressure Pipe Tapping Guide

The PVC Pipe Association has re-issued its “Tapping Guide.” The new guide includes additional diagrams and photos, as well as expanded text — all in a more logical, readable format.


John Houle

Making Sense of Diameter Types for PVC Pipe

There are many different outside diameter (OD) types used for PVC pipe for various pressure and non-pressure applications. Not only are there several OD types, there are also associated abbreviations to add to the mix.


John Houle

Guide for PVC Sewer Fittings and Laterals

Uni-Bell has recently published a new document titled, Design and Installation Guide – PVC Fittings and Laterals for Solid-Wall PVC Sewer Pipe. The guide provides information on appropriate system design and proper installation of PVC fittings products where solid-wall PVC pipe is used in non-pressure applications.


John Houle

DI vs PVC: When “Strength” is a Weakness

The Ductile Iron Pipe Research Association promotes ductile iron as “stronger” than PVC. While it is true that side-by-side laboratory testing would give the nod to DI, laboratory strength does not always transfer to real life.


John Houle

Reasons Why Water Utilities Choose PVC Pipe

Water utilities have the choice of several materials for their pipe systems. For more than 50 years, PVC’s share of the municipal water market has increased steadily at the expense of iron and other pressure-pipe materials.


John Houle

Permeation Explained

In piping systems, “permeation” is the movement of chemicals through a pipe wall or a gasketed joint. For potable water pipe, permeation is important because there may be adverse effects on the fluid inside the pipe.


John Houle

HDPE’s New “High-Strength” Material – What You Need to Know Before You Specify PE4710

The PE industry has developed a new pressure-pipe material that has been described as “high-strength.” Although the words “high-strength” sound reassuring, the reality is that pipe made from PE4710 is anything but.


John Houle

PVC Pipe: “Loss of Strength” with Time? – No!

Plastics have a material property that sets them apart from the traditional materials that most engineers studied in school. For traditional materials, there is no distinction between short-term loading and long-term loading – the material responds the same in either case. For plastics, however, there is a significant difference: plastics can handle much higher short-term loads than long-term.


John Houle

PVC Gasketed Pipe Reality: “Leakage” Not Allowed

Rumors have been circulating that AWWA standards allow gasketed pipe to leak. In fact, some websites for fused HDPE pipe include calculators that show huge “allowable” water-loss quantities based on this misperception.


John Houle

PVC vs Polypropylene (PP) Non-Pressure Pipe for Sanitary Sewers

Attached is a two-page material comparison sheet that addresses some important issues in sanitary sewer pipe selection. The document also serves as a quick reference for comparing PVC and PP non-pressure pipe.


John Houle

EPD for PVC Pipe - The Real Deal!

In the sustainability world, many manufacturers claim that their products are “green.” Often the evidence supporting these claims is flimsy at best. The recently published Environmental Product Declaration (EPD) for PVC pipe does not fall into this category.


John Houle

Deflection Mandrels for AWWA C905 Pipe

External loads usually govern the design of non-pressure pipes. For PVC sewer pipelines, one of the acceptance tests to ensure proper installation has occurred involves pulling a deflection mandrel through the pipe. Product standards for PVC gravity sewer pipes typically provide calculation methods and tables for sizing of these mandrels.


John Houle

Transitioning Between Ductile Iron and PVC Pipes

When it is necessary to transition between PVC and DI pipe, there are several considerations to keep in mind.


John Houle

ASTM D2241 Standard for PVC Pressure Pipe – 50 Years of Success

It is estimated that there are more than a million miles of installed PVC water pipe in rural communities across America – enough to go to the moon and back twice. At an average of say $20 per foot installed, that’s more than $100 billion in pipe value!


John Houle

PPI’s PACE Tool: Biased and Misleading

SHARE On its website the Plastics Pipe Institute (PPI) has a design tool called “PACE” (Pipeline Analysis and Calculation Environment), for the design of surge pressures for plastic pipes. The tool includes comparison of PE and PVC pipes.


John Houle

Time to Redefine “Large Diameter” PVC Pressure Pipe

In 1975 AWWA published the C900 standard for PVC pressure pipe and fittings. The standard’s product sizes ranged from 4-inch through 12-inch. In 1988 a second PVC pressure pipe standard was published – this standard, AWWA C905, included sizes from 14- through 24-inch.


John Houle

Time to Update Specifications for ASTM F679 PVC Sewer Pipe

In 1980 ASTM published its F679 standard for solid-wall PVC pipe and fittings. The standard’s design philosophy was to allow two wall thickness options (called “T1” and “T2”) based on two values for the PVC material’s modulus of elasticity.


John Houle

Time to Redefine “Large Diameter” Solid-Wall PVC Gravity Sewer Pipe

In 1980 ASTM published its F679 standard for solid-wall PVC pipe and fittings. The standard’s title, “Polyvinyl Chloride (PVC) Large-Diameter Plastic Gravity Sewer Pipe and Fittings,” was appropriate at the time, because the product sizes ranged from 18-inch to a maximum size of 27-inch.


John Houle

Pipe Stiffness Explained: PVC and Ductile Iron

Some project specs require Ductile Iron (DI) pipe because of its supposed “strength” in resisting external loads. In the past it was true that iron pipe had plenty of pipe stiffness, but that was before the iron industry converted from thicker-walled Class pipe to thinner-walled Pressure Class pipe.


John Houle

Looking Back 20 Years at AWWARF’s 1994 Study on PVC Water Pipe Performance

In 1994 AWWA’s Research Foundation published a report on PVC pipe titled “Evaluation of Polyvinyl Chloride (PVC) Pipe Performance.” We have now reached the 20th anniversary of the study – time for a look back to see if the research findings were accurate.


John Houle

PVC Pipe Materials: Cell-Class Explained

Product standards for PVC water and sewer pipes typically require PVC materials to meet ASTM cell-class requirements. The cell class consists of five cells that designate different aspects of the material.


John Houle

PVC Pipe Print Line – Valuable Information for Pipe Installers and Owners

Each length of PVC pipe is required by its product standard to contain a line of print that describes the pipe.


John Houle

Occasional Surge Pressure for DI and PVC Pipe: Advantage PVC

his document compares two pipe materials for response to “occasional surge,” a term that might not be well understood. AWWA standards define “occasional surge” as: Occasional (emergency or transient) surge pressure: Surge pressures caused by emergency operations, usually the result of malfunction (such as power failure, sudden valve closure, or system component failure).


John Houle

Changing Direction: Axial Join Deflection Explained

This tech brief focuses on the third method, axial deflection. Mathematically the idea is simple. For example, if you want to change direction by 5° and the allowable change in direction at each joint is 1°, then you need to deflect 5 joints.


John Houle

Joint Restraint Options for PVC Pressure Pipe

Internal pressure causes longitudinal thrust forces in pipe systems. These forces are developed at changes in flow direction or pipe size, as well as at dead ends. To keep pipe joints from pulling apart, either joint restraint or concrete thrust blocking is required.


John Houle

Important Considerations When Comparing PVC and Ductile Iron Pressure Pipe

During 60 years of sustained growth for PVC water pipe, iron pipe’s market share has decreased dramatically. The iron industry has reacted by negative attacks and by spreading misinformation about PVC pipe. I think it is time to provide more balanced information.


John Houle

Occasional Surge Pressure for HDPE and PVC Pipe: Advantage PVC

This document compares two pipe materials for response to “occasional surge,” a term that might not be well understood. So that everyone is on the same page, AWWA standards define “occasional surge” as: Occasional (emergency or transient) surge pressure: Surge pressures caused by emergency operations, usually the result of malfunction (such as power failure, sudden valve closure, or system component failure).


John Houle

Not Time to Abandon Conservative AWWA Tradition for Plastic Pipe Safety Factors

Back in 2007, the AWWA C900 standard for PVC pipe was revised. The most important change was the reduction of the standard’s safety factor from 2.5 to 2.0. A significant factor in the decision was more than 40 years of use of PVC pipe in ASTM pressure pipe applications with a safety factor of 2.0.


John Houle

Design Factor and Safety Factor Explained

There has been confusion recently in the plastic pipe industry regarding the terms “design factor” (DF) and “safety factor” (SF). Mathematically, the relationship is simple: DF is the inverse of SF. At least three AWWA standards state explicitly in the definition for DF that design factor is “the inverse of the safety factor.”


John Houle

Special Backfill Not Required for PVC Pressure Pipe

I sometimes hear the statement that PVC pressure pipe requires “special backfill," while ductile iron does not. This is a mind-set that is not based on engineering principles.


John Houle

Safe Pressure Testing of Installed Pipelines

It is common practice to pressure test installed pipelines to ensure that the pipe materials and installation are satisfactory. In fact, it makes sense that every installed pipeline be pressure tested to ensure a leak-free system.


John Houle

Dimension Ratio (DR) Explained

SHARE 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.


John Houle

PVC PIpe - Ideal for Deep Bury Projects

Some utilities are hesitant to use PVC pipe in deep-burial applications. This reluctance is based more on misconception than on engineering principles, since PVC pipe has been used for many years at depths in excess of 50 feet.


John Houle

Designers of Burried PVC Pipe Need Not Consider Collapse From Fire-Flow Pumping

There has been discussion in the piping industry about the ability of PVC pipe to withstand internal vacuum caused by pumping from fire hydrants. In fact, some designers mistakenly contend that only thicker-walled PVC pipe (DR18 or less) can resist fire-flow requirements.


John Houle

Air Valves: A Cost-Effective Way to Enhance Pressure-Pipe Performance

The presence of air in a pressure pipeline is unavoidable, since dissolved air is present in the fluid being transported. This entrained air comes out of the fluid during certain operating conditions and gathers in pockets at high spots in the pipeline.


John Houle

Correctly Assembled Gasketed PVC Pipe: Part Two

Last week’s blog entry described the importance of correctly installing PVC pipe spigots to the insertion line. This week we will look at what happens inside the pipe when the joint is assembled correctly.


John Houle

Correct Assembly of Gasketed PVC Pipe Maximizes Joint Performance

Many pipe installers think that a PVC pipe spigot is correctly installed if its insertion line has disappeared into the pipe bell. They believe that the purpose of the line is to ensure that the spigot has been installed far enough to allow the gasket to seal properly. This is only partly correct.


John Houle

UV Exposure Has No Practical Effect On PVC Pipe

As with many subjects, there is a germ of truth to the allegation: it is true that UV radiation from sunlight can affect the outermost surface of PVC pipe. However, even after prolonged exposure, there is no practical effect on the pipe’s performance characteristics.


John Houle

Cold Weather Has No Practical Effect O PVC PIpe Installation and Use

PVC pipe has been in service in North America since the 1950s and has proven its ability to function well when exposed to the rigors of cold-temperature installation and operation. PVC is widely used in Canada, Minnesota, and the Dakotas, so cold weather is not a limiting factor for PVC pipe projects.


John Houle

PVC vs Ductile Iron (DI) Pressure Pipe for Water Mains

During 60 years of sustained growth for PVC water pipe, iron pipe’s market share has decreased dramatically. The iron industry has reacted by negative attacks and by spreading misinformation about PVC pipe. We thought it was time to provide a more-balanced view.


John Houle

PVC Pipe Standards Sheets - A Valuable Resource

Each sheet provides an overview of available PVC pipe products. Included are the applicable standards as well as size ranges, material cell classes, and joining-system types.


John Houle

PVC vs PP: Not All Thermoplastics are the Same

Recent introduction of PP into the sanitary sewer market should be cause for concern to wastewater utilities. Unsupported claims about performance, lack of rigorous studies and testing, questions regarding joint integrity, reduced safety factor, limited options for fittings and lateral connections, all point to the need for caution when considering PP alternatives over PVC pipe.


John Houle