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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. 

John Houle,
Senior Technical Consultant, PVC Pipe Industry

 
PVC Pipe Bell Direction
Posted on December 8, 2016 by John Houle
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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?

The answer is “No” for hydraulics – bell direction does not affect hydraulic design.

The answer is “Yes” for installation – bell direction is important during pipe installation to facilitate problem-free joint assembly.

For details, click here for my Tech Brief.

PVC Pipe Bell Direction

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PVC Pipe Joints - Trenchless Options
Posted on October 13, 2016 by John Houle
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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.

The four joining systems are:

1.     Internally restrained gasketed joints

2.     Ring-and-pin gasketed joints

3.     Spline-lock gasketed joints

4.     Butt-fused PVC joints

For my Tech Brief on these PVC pipe joints, click here.

These restraint systems are not limited to trenchless installations. They are often used in open-cut situations where restraint is required.
  

PVC Pipe Joints - Trenchless Options

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Safety Considerations for Air-Testing of PVC Sewer Pipes
Posted on September 29, 2016 by John Houle
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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.

The story continues: “I think the pressure was too high” or “I guess the plug wasn’t installed properly.”

The danger arises from the assumption that “low pressure” means “no pressure.”

The truth is that low pressure can equate to high thrust forces on the plugs, especially for large-diameter pipes. For example, pressure of 5 psi in a 48-inch pipe creates about 9,000 pounds of thrust on the end-plug; and 9 psi in a 60-inch pipe generates almost 24,000 pounds of thrust.

There are a few simple precautions to take to protect the safety of jobsite personnel. To find out more click here for my Tech Brief titled “Safety Considerations for Air-Testing of PVC Sewer Pipes.”

Safety Considerations for Air-Testing of PVC Sewer Pipes

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An Engineering Primer on AWWA C900/C905 PVC Pipe
Posted on September 16, 2016 by John Houle
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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.

The Facts About AWWA PVC Pressure Pipe

The list of questions almost always includes the following:

  • Long-term pressure capacity
  • Short-term pressure capacity
  • Cyclic surge pressures
  • Safety factors

For discussion of these topics, click here for my Tech Brief titled “An Engineering Primer on AWWA C900/C905 PVC Pipe.” 

An Engineering Primer on AWWA C900/C905 PVC Pipe

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NEW PVC PRESSURE PIPE TAPPING GUIDE
Posted on June 22, 2016 by John Houle
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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. For those unfamiliar with the term, “tapping” refers to drilling a hole into a main-line pipe to attach a branch line. The process is often done with the main line under full pressure, so specialized techniques have been developed to streamline the installation process.

The new guide contains four major sections:

1.     Introduction

2.     Direct tapping

3.     Saddle tapping

4.     Sleeve tapping

Introduction
The introductory section provides general information that applies to all types of PVC pipe taps. Included are time-saving tips such as:

  • Use a fluted bit to allow the cut material to move away from the cutting surface.
  • Ensure that the bit has sufficient length to penetrate the full thickness of the pipe.
  • Check the removed cylindrical coupon to verify that proper techniques were used.

Also included is a section titled “Safety Considerations.”


Direct Tapping
Direct tapping is for sizes up to 1-inch, where the corp stop is screwed directly into the pipe wall. This section describes the proper equipment and techniques to cut a hole through the pipe, to cut threads into the pipe wall, and to install the corp stop — all while the main line is under pressure.

Saddle Tapping
This section is for sizes up to 2-inch, where a corp stop is screwed into a metal saddle that wraps around the pipe. The tap is accomplished by attaching a tapping machine to the corp stop and inserting the cutting bit through the corp stop to cut the hole into the pipe.

Sleeve Tapping
A tapping sleeve is required for all branch lines greater than 2-inch and up to size-on-size. The branch line is joined to the main by a connection at a metal sleeve that wraps around the pipe. The sleeve includes a flange to which to tapping machine is attached to cut the hole in the pipe.

Doing It Right
As with most construction projects, using the correct tools and employing the right techniques pays dividends. Following the recommendations of this guide will go a long way towards optimizing the installation process and preventing any problems when tapping PVC pipe.

Click here for the guide.

NEW PVC PRESSURE PIPE TAPPING GUIDE

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Thrust Forces – Restraint Length Calculator
Posted on June 16, 2016 by John Houle
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Thrust forces are developed in a pressure pipe whenever there is a change in flow. This means that thrust restraint may be required when the pipeline changes direction (for example, at an elbow), changes size (at a reducer), or encounters a stoppage in flow (for example, at a closed valve).

Complicated Design Simplified by EBAA’s Calculator

Thrust-restraint design can be complicated, with as many as eight variables to consider.

Fortunately, EBAA Iron has developed an on-line design tool that makes the engineer’s job easier. The designer simply inputs the variables requested and the calculator provides the length of pipe that must be restrained to control pipe movement. The program also provides an output page that lists all of the design inputs, as well as the resulting thrust force and required restraint length.

For my Tech Brief on EBAA Iron’s on-line calculator for restraining PVC pipe joints, click here.

Thrust Forces – Restraint Length Calculator

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External Joint-Restraint Devices for PVC Pipe
Posted on June 10, 2016 by John Houle
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Thrust forces are developed in a pressure pipe whenever there is a change in flow. When joint restraint is required to accommodate these forces, the most commonly used method is external joint-restraint devices. These devices have been used successfully on PVC pipe for more than 25 years.

For my Tech Brief on external joint-restraint devices for PVC pipe joints, click here.

Typically, a restrained length of pipe is required on both sides of an appurtenance. The length of pipe to be restrained is determined by the design engineer. To restrain that pipe length, pipe-to-fitting restraints (usually MJ) and pipe-to-pipe restraints (bell harness) are usually required.

As usual on pipeline projects, there are methods of installation that provide better results. Tightening of nuts on threaded hardware is a good example. The Tech Brief discusses three types of threaded connection and how to best accomplish them.

External Joint-Restraint Devices for PVC Pipe

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Installation of PVC Pipe into a Mechanical Joint (MJ)
Posted on May 25, 2016 by John Houle
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A “mechanical joint” (MJ) is defined in ASTM Standard D3139 as: “a joint in which a positive seal is achieved when a gasket is compressed by means of a mechanical device.” The MJ connection is very commonly used in North American pressure pipelines and usually is installed without any problems.

Occasionally, however, I hear of projects where there are issues with MJs.

Correct Installation Methods Minimize Problems

As with most construction projects, successful installations occur when tried-and-true methods are used. For any pipeline installation where bolts and nuts are used, it is important to tighten the bolts in the correct order (a “star pattern”) and to tighten the bolts to the correct torque value. In the case of an MJ, failure to follow these simple guidelines can result in leaks or other problems.

For my Tech Brief on PVC pipe and mechanical joints, click here.

Installation of PVC Pipe into a Mechanical Joint (MJ)

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PVC Pipe and Diesel Exhaust
Posted on May 2, 2016 by John Houle
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The presence of diesel exhaust residue on PVC pipe does not mean that the pipe should be rejected. In fact, if the pipe is intended for non-potable usage, the exhaust deposits are not a cause for concern.

For potable water applications, however, the interior of the pipe should be protected from the exhaust. If exhaust residue is present in an installed water pipe, the resulting odor is difficult to remove and can be detected in the drinking water.

Of course, it is much easier to prevent a problem than it is to fix one after it has occurred. For this reason, the exhaust should be directed away from the pipe or the pipe should be protected by smoke tarps. Pipe producers typically require that truckers provide smoke protection for pipe that might be exposed to exhaust.

Even if the interior of a water pipe becomes stained by exhaust, it is not necessary to reject the pipe. Instead, the pipe should be cleaned before installation.

For more information on diesel exhaust, click here.

PVC Pipe and Diesel Exhaust

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PVC Water and Sewer Pipe - Lead Free
Posted on April 18, 2016 by John Houle
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City of Flint, Michigan

News about lead-poisoning from old service-line piping has been widespread in the media recently. It seems that the City of Flint switched to a different drinking-water source in an attempt to provide lower-cost water to its residents. The change caused unintended consequences, as the more-aggressive chemistry of the new water caused lead to leach from some of the city’s service pipes.

The thoughts and prayers of Uni-Bell staff and member-company personnel are with those who have suffered from this situation. We all hope that a timely and equitable solution will be found to remedy the problems in Flint.

PVC Pipe – No Lead

Occasionally I hear questions asking if lead can leach from PVC pipes. With lead-poisoning now a universal topic of interest in the water community, I decided that this would be the right time to write a technical document on the subject.

The truth is that lead does not leach from PVC pipe because there is no lead used in its manufacture – no lead in its raw materials and no lead in its processing.

For my Tech Brief on PVC pipe and lead, click here.

PVC Water and Sewer Pipe - Lead Free

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Making Sense of Diameter Types for PVC Pipe
Posted on April 4, 2016 by John Houle
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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.

The topic can be approached in a logical manner by separating the pipe types for each standards organization and end-use application:

  • AWWA pressure pipe
  • ASTM pressure pipe
  • ASTM solid-wall sewer pipe

For a discussion of different OD regimens and their descriptive acronyms, click here to read my Tech Brief.

Making Sense of Diameter Types for PVC Pipe

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Guide for PVC Sewer Fittings and Laterals
Posted on February 22, 2016 by John Houle
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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.
 
The guide covers fittings that are available for various dimension ratios and outside diameters of PVC pipe through 60-inch. The information on installation practices is intended to help utilities optimize the performance of PVC fittings. Using PVC fittings with PVC pipe enables utilities to construct their sewer-pipe systems from one material – corrosion-proof PVC.
 
Contents include:
  • List of standards applicable for PVC fittings products and installation
  • Suggested specification language
  • Products available: wide assortment of PVC fitting configurations
  • Design guidance: topics such as burial depth, soil compaction, and accommodating pipe movement
  • Installation considerations and recommendation
For a quick overview of what the guide offers, click here to read my Tech Brief.
Guide for PVC Sewer Fittings and Laterals

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DI vs PVC: When “Strength” is a Weakness
Posted on February 3, 2016 by John Houle
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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.

A case in point is surge pressures. Ductile iron has a higher tensile modulus of elasticity than PVC, which means that any surges generated in DI pipe will be higher than in PVC pipe.

This tech brief uses the design example in the AWWA C900 PVC pipe standard to compare surges in DR18 PVC pipe and PC350 ductile iron pipe. As expected, the DI surges are much higher – so high that:

  • Total pressure in the DI pipe exceeds its allowable pressure capacity
  • System appurtenances might be at risk

Conventional wisdom is turned on its head: “strength” is sometimes a disadvantage.

Click here to read the Tech Brief.

DI vs PVC: When “Strength” is a Weakness

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Reasons Why Water Utilities Choose PVC Pipe
Posted on January 14, 2016 by John Houle
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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.

The reasons why so many utilities use PVC include:
• Lower initial cost
• Ease of installation
• Compatibility with existing pipe inventories
• Availability of trenchless options
• Design life of 100+ years

For discussion of these and other reasons for PVC’s growth, click here to read my Tech Brief.

Reasons Why Water Utilities Choose PVC Pipe

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Permeation Explained
Posted on December 16, 2015 by John Houle
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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.

Starting in the 1970s, there has been a significant amount of research on permeation. This Tech Brief looks at some of that research, discussing permeation in PVC pipe, in HDPE pipe, and in gasket materials used for PVC pipe joints. Since gasoline is a common contaminant that comes into contact with municipal pressure pipe, there is special emphasis on gasoline permeation.

PVC pipe is well-suited for gasoline-contaminated soils. In contrast, HDPE is not suitable for piping projects where contamination currently exists or may exist in the future.

Click here for my Tech Brief on this subject.

Permeation Explained

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HDPE’s New “High-Strength” Material – What You Need to Know Before You Specify PE4710
Posted on December 11, 2015 by John Houle
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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.

The reason is that the new material has the same Hydrostatic Design Basis (HDB) as the earlier-generation PE3608. For both materials, the HDB = 1600 psi per the appropriate standards and test methods. For comparison, PVC’s HDB is 4000 psi.

The obvious question is: how can a PE material be “higher-strength” if its strength is the same?

The answer is that the material can appear to be higher strength if a lower safety factor is used.

One example should suffice: let’s compare Pressure Class 100 psi (PC 100) pipe made from PE3608 and from PE4710. The AWWA C906 standard requires the minimum burst strength to be 365 psi for the lower-strength PE3608. For the new “higher-strength” PE4710 material, the burst strength is only 290 psi. This means the “higher-strength” PE4710 pipe has burst strength 75 psi lower!

The Tech Brief looks at this and three other items that you should be considering as you investigate PE4710. Click here to read.

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

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PVC Pipe: “Loss of Strength” with Time? – No!
Posted on October 22, 2015 by John Houle
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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.

A quick example: AWWA C900 DR18 pipe has a long-term rating of 235 psi, but its short-term rating jumps up to 376 psi. This is equivalent to hoop stresses of 2000 psi and 3200 psi, respectively. For this example, the short-term rating is 60% higher than the long-term rating.

When a log-log plot is made of PVC pipe stress at failure vs. time of load application, the failure points will lie along a line that slopes downward as time increases. This is logical, given the discussion above.

Proponents of non-plastic materials have chosen to use this downward-sloping line as evidence that PVC pipe “loses strength with time” or “degrades over time.” However, this is not the case – the line’s slope merely proves that PVC pipe can withstand higher short-term stresses than long-term stresses.

To read more, click here for the Tech Brief on this subject.

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

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PVC Gasketed Pipe Reality: “Leakage” Not Allowed
Posted on September 21, 2015 by John Houle
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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.

Nothing could be further from the truth.

The reality is that AWWA standards do not allow pipes to leak. AWWA documents include pressure and leakage tests to verify that newly installed pipelines have proper materials and installation. These documents include what is known as “make-up water” to accommodate variables in testing such as entrapped air, movement of pipeline components, and slight increase in pipe diameter. However, the standards state that leaks discovered during testing must be repaired.

Click here for the Tech Brief on this subject.

PVC Gasketed Pipe Reality: “Leakage” Not Allowed

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PVC VS. POLYPROPYLENE (PP) NON-PRESSURE PIPE FOR SANITARY SEWERS
Posted on June 25, 2015 by John Houle
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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. Click here to read.

The long-standing technique for making a decision is to draw a vertical line down the middle of a piece of paper, listing the positives to the left and the negatives to the right. If you follow this process for PVC pipe, you will find the left side filled with positive attributes. Here are a few:

Longevity
PVC has become the material of choice for sanitary sewers because of long-term reliability coupled with low maintenance requirements.

Joint Integrity
PVC joints are designed to be leak-free when tested at 25 feet of head per ASTM D3212. This is a stringent test method that includes testing joints that are deflected both radially and longitudinally to simulate extreme jobsite conditions.

Stringent Post-Installation Acceptance Tests
Low-pressure air testing and deflection-mandrel testing are routinely performed on installed PVC sanitary sewer lines. Because of PVC pipe’s material properties, these tests have proven to provide a high degree of assurance that the installed lines will perform as designed.

I encourage you to compare and contrast the two materials. The conclusion I reached is that PVC’s positive attributes are reasons to keep any unproven pipe material on the sidelines. In this case, I would kick PP to the curb until it has shown itself to be a viable product for the long term.

PVC VS. POLYPROPYLENE (PP) NON-PRESSURE PIPE FOR SANITARY SEWERS

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EPD FOR PVC PIPE - THE REAL DEAL!
Posted on June 8, 2015 by John Houle
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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. The document was:

  • Developed in compliance with International Standards Organization (ISO) standards.
  • Certified by NSF Sustainability, a division of NSF International.
  • Based on a Life Cycle Assessment (LCA) developed by Sustainable Solutions Inc. that was reviewed by an independent third-party panel of sustainability experts.

The PVC pipe industry did it right. Other pipe materials should do the same.

Click here to read the PVC pipe EPD.

EPD FOR PVC PIPE - THE REAL DEAL!

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DEFLECTION MANDRELS FOR AWWA C905 PIPE
Posted on May 14, 2015 by John Houle
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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.


AWWA standards, on the other hand, are intended for pressure applications – hence there are no mandrel discussions, calculation methods, or tables provided.

The Technical Brief “Sizing of Deflection Mandrels for AWWA C905 Pipe” addresses this issue by explaining the calculation method and providing mandrel sizes for 14- to 48-inch CIOD pipe.

To find out more, click here to read the Tech Brief.

DEFLECTION MANDRELS FOR AWWA C905 PIPE

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Transitioning Between Ductile Iron and PVC Pipes
Posted on December 10, 2014 by John Houle
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When it is necessary to transition between PVC and DI pipe, there are several considerations to keep in mind.

First, although both products are made to the same Cast-Iron outside diameter (CIOD) regimen, ductile iron pipe tolerances are much looser than those for PVC pipe. This has an effect on some joining situations.

Second, the geometry of the two products’ spigot ends is very different. This means that inserting PVC bells into DI spigots is easily accomplished, while inserting DI spigots into PVC bells is more problematic.

To find out more, click here to read the Tech Brief.

Transitioning Between Ductile Iron and PVC Pipes

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ASTM D2241 Standard for PVC Pressure Pipe – 50 Years of Success
Posted on November 18, 2014 by John Houle
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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!

The majority of this pipe was manufactured to ASTM D2241, which is celebrating its 50th anniversary this year.

ASTM D2241 pipe has also been installed in many municipal water and forcemain systems. Prior to the introduction of AWWA C900 in 1975, D2241 pipe was the product of choice for PVC pressure pipe systems, so it is not just a rural product.

ASTM D2241 has played a significant role in U.S. piping infrastructure by providing the requirements for materials, dimensions, and product testing that has ensured users a high-quality pipe product.

To read my Tech Brief on this subject, click here.

Congratulations, D2241, as you enter your second half-century!

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

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PPI’s PACE Tool: Biased and Misleading
Posted on October 21, 2014 by John Houle
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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.

However, it is important to realize that although the word “Plastics” appears in its name, PPI does not speak for PVC. In fact, PPI has misrepresented PVC in favor of PE.

PACE is an example.

While the tool itself is functional, restrictions placed on the input variables force the results to be skewed in favor of PE. I tried to use PACE to verify the design example in the AWWA C900 standard for PVC pipe, but could not because PACE will not allow the use of the standard’s inputs!

To find out more, click here to read the Tech Brief.

The Irony of It All

The PVC pipe industry has procedures for determination of allowable surge pressures based on safety factors, material properties, and cyclic pressure research. This point is clarified by reviewing:

  1. AWWA PVC pipe standard C900-07
  2. Cyclic surge testing research – for example, “PVC Pressure Pipe Endures Over Ten Million Cycles” click here.

By contrast, PE has less rigorous justification for its cyclic-surge design methodology. AWWA Standard C906 for polyethylene pipe contains only design values without any technical explanations.

The Bottom Line

Driven by PPI’s interest to develop design tools that favor PE, PPI has intentionally mandated that only highly unlikely design assumptions and inputs be used for PACE when it comes to PVC pipe. The flawed results produced for PVC pressure pipe are not consistent with its performance in the field over many decades or studies confirming PVC pipe longevity at more than 100 years. 

PPI’s PACE Tool: Biased and Misleading

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Time to Redefine “Large Diameter” PVC Pressure Pipe
Posted on September 30, 2014 by John Houle
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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.

The two standards differed markedly in their product design: C900 used a safety factor of 2.5, while C905 employed an SF of 2.0. Because of this distinctly different design approach, there was an obvious break between small diameter pipe (4- through 12-inch) and large-diameter pipe (14- through 24-inch.)

In the 26 years since C905 was published, however, three major changes have occurred that make the transition point to large diameter less clear:

  1. The design methods in the two standards have been harmonized.
  2. A revision is now under way at AWWA to merge the two standards under the C900 title.
  3. The largest size being produced has more than doubled to 60 inches.

What was considered “large-diameter” in 1988 is now relatively small. Unfortunately, some specifiers still consider 14-inch as a large pressure pipe – with 60-inch as the comparison, I think it is time to revisit the definition of “large-diameter.”

Click here for my Tech Brief on this subject.

PVC’s market share for potable water mains and sewer forcemains in North America has been growing steadily for more than 50 years. The large market share gained by smaller-diameter PVC pipe is a result of the product’s outstanding performance characteristics – the same advantages that are provided by larger-diameter products. 

Time to Redefine “Large Diameter” PVC Pressure Pipe

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Time to Update Specifications for ASTM F679 PVC Sewer Pipe
Posted on September 23, 2014 by John Houle
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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.

In 2006 this design method was changed. Gone are the “T1” and “T2” wall designations.

Instead the new system provides a minimum wall thickness table combined with minimum pipe stiffness values – the pipe manufacturer is now able to provide the targeted pipe stiffness with any combination of wall thickness and modulus of elasticity (as long as material cell class and minimum wall thickness requirements are met).

Click here for my Tech Brief on this subject.

The bottom line: project specifications that call out “T1” or “T2” walls are outdated – these references have been obsolete for about eight years.

Time to Update Specifications for ASTM F679 PVC Sewer Pipe

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Time to Redefine “Large Diameter” Solid-Wall PVC Gravity Sewer Pipe
Posted on September 17, 2014 by John Houle
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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.

In the thirty-four years since 1980, however, the maximum size more than doubled to 60 inches. What was considered “large” in 1980 is now relatively small.

Unfortunately, some specifiers still consider 18-inch as a large sewer pipe – with 60-inch as the comparison, I think it is time to revisit the definition of “large-diameter.”

Click here for my Tech Brief on this subject.

PVC sewer pipe has been the product of choice for sanitary sewers in North America for more than 25 years. The large market share gained by smaller-diameter PVC pipe is a result of the product’s outstanding performance characteristics – the same advantages that are provided by larger-diameter products.

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

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Pipe Stiffness Explained: PVC and Ductile Iron
Posted on June 11, 2014 by John Houle
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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.

Conventional Wisdom Is Not Always True

This tech brief discusses how much a pipe can safely deflect – PVC is safer.

Pipe stiffness of two approximately equal pressure class pipes is compared – PVC is stiffer.

The facts:

  • DI pipe fails at a lower deflection than PVC pipe.
     
  • DI has a lower safety factor against failure.

Conventional wisdom is turned on its head: the stronger, safer pipe is PVC!

To find out more, click here for the Tech Brief.

Pipe Stiffness Explained: PVC and Ductile Iron

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Looking Back 20 Years at AWWARF’s 1994 Study on PVC Water Pipe Performance
Posted on May 14, 2014 by John Houle
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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.

I’ve tried to keep you in suspense, but the answer is a resounding “Yes.” The report’s assertions have proven correct and time has reinforced its conclusions. For example:

  • The allegation that PVC “loses strength with time” has been disproved.
     
  • Tapping PVC pipe was not a problem back then and is less so today with improvements in hardware, procedures, and tapping.
     
  • UV exposure and chemical permeation of PVC pipe were shown by AWWARF to be non-issues 20 years ago and the passage of time has borne this out.

Click here for my Tech Brief on this subject.

PVC water pipe was in widespread use in North America 20 years ago, but has now become the product of choice – it is a well-engineered product that provides exceptional service for water transmission and distribution systems.

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

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PVC Pipe Materials: Cell-Class Explained
Posted on April 29, 2014 by John Houle
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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.

This tech brief discusses cell class and what all those numbers mean. It also takes issue with two industry misconceptions:

  • The 12364 cell class is “new” – the truth is that this class has been in ASTM standards for about 35 years – this is not new!
     
  • PVC cell class is 5 numbers plus one letter – this was correct in the past, but ASTM eliminated the letter more than 15 years ago – this is not new either!

To find out more, click here to read the Tech Brief.

PVC Pipe Materials: Cell-Class Explained

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PVC Pipe Print Line – Valuable Information for Pipe Installers and Owners
Posted on April 15, 2014 by John Houle
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Each length of PVC pipe is required by its product standard to contain a line of print that describes the pipe.

Print information should be checked at several locations:

  1. At the manufacturing plant to ensure that the correct pipe is being shipped
  2. At the jobsite or storage yard to confirm that the pipe that was purchased is the pipe that has been received
  3. At the trench to ensure the specified pipe is being installed
  4. Any time the pipe is exposed after installation

The attached technical brief explains the details of print requirements and provides an example print line. Click here.

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

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Occasional Surge Pressure for DI and PVC Pipe: Advantage PVC
Posted on April 1, 2014 by John Houle
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This 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).

The design assumption is that an emergency event would occur at most only a few times in the life of the pipeline. For this reason, occasional surge is analyzed differently from “recurring surge” (also known as “cyclic surge”), which is a design condition for sewer forcemains.

The ductile iron (DI) industry promotes their material as superior to PVC for surge pressures. The attached comparison uses the same set of design conditions to compare PVC and DI for occasional surge pressure. See for yourself – both products are suitable for the static pressure, but the total pressure (including surge) in the DI pipe is 495 psi compared to 282 psi in the PVC pipe.

For ductile iron the total pressure is at 110% of the allowable pressure – redesign would be required. Meanwhile, for PVC the total pressure is only 75% of allowable.

Furthermore, the 495 psi pressure in the DI pipe might damage non-pipe components such as valves, fittings, and service lines.

Click here to read.

Occasional Surge Pressure for DI and PVC Pipe:  Advantage PVC

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Changing Direction: Axial Joint Deflection Explained
Posted on February 14, 2014 by John Houle
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There are three ways to change a gasketed pipeline’s direction:

  1. Fitting (elbow, bend, etc.)
  2. Curvature of the pipe barrel
  3. Axial deflection at pipe joints

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.

The document explains this concept and the geometry involved. Click here to read.

Design Aid

There are two links in the tech brief -- the first is to a design aid. The designer initially inputs two variables:

  1. Total angle to be turned
  2. Allowable angle per joint (from the manufacturer of the pipe to be used)

The first output is the number of joints necessary. After adjusting the number of joints to a whole number, the designer then inputs a third variable: the distance between joints. Outputs are the offset at the end of the deflected pipe and the radius of curvature of the pipeline.

Offset Tables

The second link is to a series of tables that show the linear offsets from the original undeflected pipeline for different allowable angles.

This information should be helpful to a designer in deciding which method to use to curve a pipeline.

Changing Direction: Axial Joint Deflection Explained

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JOINT RESTRAINT OPTIONS FOR PVC PRESSURE PIPE
Posted on January 17, 2014 by John Houle
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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.

In the past, concrete thrust blocks were the most commonly used method to prevent movement. Recently, thrust blocking has largely given way to joint restraint.

There are several methods for restraining PVC pipe joints. In addition to the traditional external joint restraint devices, several integral internal devices have been developed.

The attached technical brief provides background on this topic. Click here to read.

JOINT RESTRAINT OPTIONS FOR PVC PRESSURE PIPE

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Important Considerations When Comparing PVC and Ductile Iron Pressure Pipe
Posted on November 13, 2013 by John Houle
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The Decline of Iron 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.

PVC Pipe – Healthy and Safe

PVC is used in over 40,000 municipalities in North America because it meets health and safety regulations – some 10 million quality tests have been conducted on water carried through PVC pipe since it was introduced. Health and safety are major reasons why most new installations of drinking-water distribution pipe are PVC.

Why the Move from Iron to PVC?

The major cause: corrosion of iron pipe. To make matters worse, thinner-walled ductile iron (DI) corrodes sooner than traditional cast iron pipe products.

Transitioning from Iron to PVC Pipe: A Smooth and Seamless Process

The DI industry has argued that the transition to PVC is so difficult it would be better to stay with underperforming iron. In fact, the typical move to PVC has been very straightforward:

• Same outside diameters – for the municipal water market, PVC pipe and DI pipe are manufactured in the same cast-iron outside diameter regimen.

• Same fittings, valves, and appurtenances – the same slip-on or mechanical joint fittings, valves, and appurtenances used with DI can be used with PVC pipe in the same manner. This ensures that product styles and installation procedures will be familiar to the waterworks professional.

• Same suppliers – all items needed for PVC water systems are available from the same suppliers that provide DI items.

Comparison Sheet

Attached is a comparison sheet that addresses important issues in water pipe selection and serves as a quick reference for comparing PVC and DI pressure pipe. Click here to read.

Important Considerations When Comparing PVC and Ductile Iron Pressure Pipe

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Occasional Surge Pressure for HDPE and PVC Pipe: Advantage PVC
Posted on October 30, 2013 by John Houle
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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).

The thinking is that an emergency event would occur at most only a few times in the life of the pipeline. For this reason, occasional surge is analyzed differently from “recurring surge” (also known as “cyclic surge”).

The polyethylene (HDPE) pipe industry is promoting their material as superior to PVC for surge pressures. The attached comparison uses the same set of design conditions to compare PVC and HDPE for occasional surge pressure. See for yourself – both products are suitable for the application, but the surge generated in the HDPE pipe is 341 psi compared to 282 psi in the PVC pipe. While both pipe materials would fare well, the additional 20% higher surge in the PE pipe might damage non-pipe components such as fittings and valves.

Click here to read.

Occasional Surge Pressure for HDPE and PVC Pipe: Advantage PVC

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Not Time to Abandon Conservative AWWA Tradition for Plastic Pipe Safety Factors
Posted on October 23, 2013 by John Houle
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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.

Fast-forward to 2013 – the HDPE industry is proposing to reduce its safety factor for a new material from 2.0 down to 1.6. This material does not have a long history of usage and therefore has unknown longevity – paradoxically, it would also have the lowest safety factor of any AWWA pipe used for transmission/distribution applications.

The attached technical brief discusses the contrast between the evolution of safety factors for PVC and HDPE. Click here to read.

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

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Design Factor and Safety Factor Explained
Posted on October 16, 2013 by John Houle
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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.”

The attached technical brief discusses the relationship between the two concepts in more detail. To further illustrate the point, the brief includes a table of numerical examples from AWWA product standards for plastic transmission/distribution pipe. In all cases the design factor is 0.50 and the safety factor is 2.0.

Click here to read.

 

Design Factor and Safety Factor Explained

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Special Backfill Not Required for PVC Pressure Pipe
Posted on October 2, 2013 by John Houle
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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.

The attached “Backfill Requirements for PVC Pressure and Gravity Pipes” sets the record straight by investigating the concepts of pipe stiffness and pipe deflection. Examples are included using low-quality uncompacted backfill. Even in these extreme conditions, the result is that PVC DR18 and DR14 pressure pipes (the typical PVC municipal pipes) experience in-ground pipe deflections that are less than one-fifth of the allowable deflections.

It is clear that uncompacted native soil provides enough support to keep pipe deflections very low – insistence on costly imported backfill is a waste of an owner’s money.

AWWA Standards – Same for DI and PVC

AWWA installation standards recognize that PVC and ductile iron do not require different backfill. In fact, the AWWA C600 standard (ductile iron) and the AWWA C605 standard (PVC) each include drawings of five trench types. Close inspection of these trench types shows that the two standards have identical requirements.

PVC Gravity Sewer Pipe – a Different Story

It is likely that the “special backfill” mentality arose because of PVC gravity pipe. Gravity pipe is used in high-load conditions:

  • Extremely shallow burial (as little as 1 foot) with highway loads
  • Very deep burial (in excess of 50 feet) with significant soil loads

These high loads cause backfill material and compaction to become critical components of the engineer’s design.

For details, please see the attached technical brief. Click here to read.

Correction: In my previous blog entry on air testing of installed sewer pipe, I wrote “Gravity pipe is typically tested with low-pressure air (usually 5 psi).” The correct pressure is 4 psi.

 

Special Backfill Not Required for PVC Pressure Pipe

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Safe Pressure Testing of Installed Pipelines
Posted on September 10, 2013 by John Houle
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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.

Gravity Sewer Pipe

Gravity pipe is typically tested with low-pressure air (usually 4 psi). The maximum recommended air pressure is 9 psi, which seems like a safe pressure. However, if an end-plug were to let go in a large-sized pipe, even a low-pressure test could pose a safety threat.

Pressure Pipe

Pressure pipe is tested at much higher pressures, often at the pressure class of the pipe. Because air is a compressible medium, air under high pressure stores a large amount of potential energy. A failure of any component in the system would result in the air’s potential energy turning into kinetic energy, with dangerous consequences. For this reason, the most unbreakable rule in the pipe industry is: DO NOT USE AIR TO TEST PRESSURE PIPE.

Click here to read.

  

Safe Pressure Testing of Installed Pipelines

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Dimension Ratio (DR) Explained
Posted on May 23, 2013 by John Houle
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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.

 

Dimension Ratio (DR) Explained

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PVC Pipe – Ideal for Deep-Bury Projects
Posted on May 15, 2013 by John Houle
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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.

The attached technical brief concentrates on the science of the subject. Click here to read.

PVC Pipe Stands Up to Large Earth loads

Some engineers insist on using iron pipe over a certain depth – while the rest of the sewer main is PVC – because they fear PVC won’t hold up under large dead loads.

The fact is that buried PVC pipe does not act alone – it receives support from the surrounding soil. The combined pipe/soil structural system allows PVC pipe to be buried at depths not possible for “stronger” rigid pipes.

Long Life for Deep Bury

The two example projects in the document show that deep-bury PVC pipe continues to function well over time: one installation is from 1995 (18 years) and the other from 1986 (27 years).

 

PVC Pipe – Ideal for Deep-Bury Projects

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Designers of Buried PVC Pipe Need Not Consider Collapse From Fire-Flow Pumping
Posted on April 17, 2013 by John Houle
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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.

The attached technical brief provides the engineering to dispel this misconception.
Click here to read.

The fact is that buried PVC pipe receives support from the soil that surrounds it. Design examples in the document assume a low value for the soil capacity – despite this very conservative assumption, thin-walled SDR41 pipe would not experience collapse due to fire-flow conditions. An engineer who designs buried PVC pipe does not need to consider collapse from fire-flow pumping.

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

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Air Valves: A Cost-Effective Way to Enhance Pressure-Pipe Performance
Posted on April 10, 2013 by John Houle
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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.

Air Pockets Increase Operating and Maintenance Costs

Research has shown that air pockets in pressure piping systems cause increased operating costs and can result in pipeline damage. Air pockets decrease flow capacity and cause significant energy losses. They can also produce or enhance surge pressures, which can cause severe damage to pipelines.

The solution is air valves, the subject of the attached technical brief. Click here to read.

Correctly designed, installed, and maintained air valves are the most cost-effective tools to control entrained air and air pockets in pressurized piping systems.

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

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Correctly Assembled Gasketed PVC Pipe: Part Two
Posted on April 3, 2013 by John Houle
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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.

Expansion Gaps: Important for PVC Pipe Joint Design

With correct installation, there is a horizontal gap inside the joint between the end of the spigot and the shoulder of the bell. This gap is the subject of the attached technical brief. Click here to read. The gap occurs in both pressure and non-pressure pipe, but is observable only during video inspection of gravity-flow sanitary sewer pipe.

The gap is necessary to provide room for thermal expansion of the pipe and to allow for angular joint deflection that accommodates any ground movement that occurs. The gap is an integral feature of the joint design and does not affect the joint’s water-tightness or its hydraulic characteristics.
 

Correctly Assembled Gasketed PVC Pipe: Part Two

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Correct Assembly of Gasketed PVC Pipe Maximizes Joint Performance
Posted on March 27, 2013 by John Houle
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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.

As the attached technical brief explains (click here), there is more than one purpose for the insertion line:

  1. The first purpose is to ensure that the gasket will properly engage with the spigot to form a leak-free joint. If there is a space between the line and the bell, sealing may be affected.
     
  2. The second reason is to prevent the spigot from being inserted too far into the bell. If the line is not visible, the spigot has been over-inserted.

Thus, the insertion line is barely visible in properly installed PVC pipe.

Over-insertion is not ideal because it defeats some of the benefits of PVC pipe joint design:

  • Less room for the joint to accommodate thermal expansion
  • Reduced ability to axially deflect the joint (to change direction)
  • Possible creation of stress in the bell wall

Sixty years of experience have shown that PVC pipe joints function reliably long-term even when not installed perfectly. However, the recommendations of the technical brief should be followed to maximize joint performance.

 

Correct Assembly of Gasketed PVC Pipe Maximizes Joint Performance

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UV Exposure Has No Practical Effect on PVC Pipe
Posted on March 20, 2013 by John Houle
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The effect of sunlight on PVC pipe has been a misunderstood topic. Negative attacks by our competitors allege that exposure to sunlight causes PVC pipe’s properties to degrade so severely that the pipe becomes unsuitable for use. The attached technical brief rebuts this contention. Click here

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.

Two-Year UV Exposure Study

A two-year study has quantified the effects of UV radiation on the properties of PVC pipe. The research found that exposure to UV radiation results in a change in the pipe’s surface color and a reduction in impact strength. Other properties such as tensile strength (pressure rating) and modulus of elasticity (pipe stiffness) are not adversely affected.

It is important to realize that the average impact strength after two years of exposure still remained above the level required at time of manufacture. There are no restrictions on cutting or tapping of UV-discolored PVC pipe. As well, UV-exposed pipe can still be installed with less care than is necessary for more vulnerable clay, concrete, or mortar-lined/epoxy-coated ductile iron alternatives.

The Bottom Line

On a practical basis, exposure to UV radiation has no performance-based effect on PVC pipe.

 

UV Exposure Has No Practical Effect on PVC Pipe

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Cold Weather Has No Practical Effect on PVC Pipe Installation and Use
Posted on March 13, 2013 by John Houle
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Negative attacks made by our competitors allege that PVC pipe is not suitable for cold-weather projects. The attached technical brief refutes this claim. Click here.

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.

In fact, installation of PVC pipe is even more advantageous as temperatures decrease and workers become hampered by inclement weather conditions. PVC is ideal in these situations because it is easy to cut, easy to handle, and easy to assemble.

This technical brief discusses three aspects of PVC pipe in cold temperatures:

  1. Design
     - Effects on PVC’s material properties
     - Accommodating thermal expansion
     - How to prevent freezing
     
  2. Handling and Installation
     - Effects on PVC’s material properties
     - Accommodating thermal expansion
     - How to prevent freezing
     
  3. Operations – no change from typical operations

There are three key messages:

  1. In cold conditions, installation practices are important for all piping – abusive handling practices should not be used with any pipe material.
     
  2. Worker safety should always be paramount – prolonged exposure to cold temperatures may affect workers’ productivity and performance.
     
  3. PVC pipe is a logical choice for cold-weather projects.

Stay tuned for my next blog entry when I will address misconceptions about the effects of UV exposure on PVC pipe.

Cold Weather Has No Practical Effect on PVC Pipe Installation and Use

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PVC vs. Ductile Iron (DI) Pressure Pipe for Water Mains
Posted on March 6, 2013 by John Houle
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Attached is a two-page comparison sheet that addresses some important issues in water pipe selection and serves as a quick reference for comparing PVC and DI pressure pipe. Click here.

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.

Health and Safety

PVC is used in over 40,000 municipalities in North America because it meets all health and safety regulations – some 10 million quality tests have been conducted on water carried through PVC pipe since it was introduced. Health and safety are major reasons why most new installations of drinking-water distribution pipe are PVC.

Why the Move from Iron to PVC?

A combination of two factors is driving the move from iron to PVC:

Transitioning from Iron to PVC Pipe: A Smooth and Seamless Process

The DI industry has argued that the transition to PVC is so difficult it would be better to stay with underperforming iron. In fact, the typical move to PVC has been smooth and seamless. Here are the facts:

  • Same outside diameters – for the municipal water market, PVC pipe and DI pipe are manufactured in the same cast-iron outside diameter regimen.
  • Same fittings, valves, and appurtenances – the same slip-on or mechanical joint fittings, valves, and appurtenances used with DI can be used with PVC pipe in the same manner. This ensures that product styles and installation procedures will be familiar to the waterworks professional.

We encourage you to contrast and compare and to include PVC pipe in your upcoming water project bids. Join the growing number of North American water utilities that are providing greater value for taxpayer dollars by using PVC pipe – installing better-performing pipe while simultaneously reducing capital and O&M costs.

 

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

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PVC Pipe Standards Sheets - A Valuable Resource
Posted on February 21, 2013 by John Houle
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I would like to direct your attention to our standards sheets, one of the Association’s key resources:

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. The pressure-pipe sheets also provide outside-diameter regimens and pressure classes/ratings, while the gravity-sewer sheet includes pipe stiffness values for both solid-wall and profile-wall pipes.

Some might not realize the extent of the size ranges available. For PVC pressure pipe, the maximum size is 48-inch. For PVC gravity pipe, the largest solid-wall pipe is also 48-inch, with profile-wall pipe up to 60-inch.

PVC Pipe Standards Sheets - A Valuable Resource

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PVC vs. PP: Not All Thermoplastics Are The Same
Posted on June 10, 2011 by Steve Cooper
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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.

Thermoplastic materials have different engineering properties and standards, and it's important for engineers, contractors and sewer departments to recognize them. Otherwise they risk compromising long-term performance.

Uni-Bell's PVC vs. PP comparison sheet (click here) summarizes these differences, ranging from why bell stiffeners are required for PP, to allowable deflection limits and the corresponding safety factor – confirming PVC pipe's superior performance.  

Supported by over 40 years of standards and testing, PVC pipe offers exceptional joint integrity, low maintenance and a high safety factor, backed by stringent mandrel and low-pressure air tests. With a broad assortment of fittings for connections, which help avoid compromising system integrity through use of cut-in fittings, PVC pipe is available in a wide array of options suitable for the most difficult applications.

With more than one million miles in service,  and manufactured in sizes ranging for 4-60 inches, PVC is the most widely used material for gravity sewer pipe with an estimated market share in excess of 80%.

The quality and performance of PVC have been validated by countless universities, government agencies, engineers, installers and utilities.  As well,  it was ranked highest in a 2010 buried pipe market survey by Trenchless Technology  Magazine  and rated as the most commonly specified, easiest to maintain and longest-lasting pipe material.  See pages 8-11 of the study by clicking on the following link:

http://www.trenchlessonline.com/pdfs/2010_Pipe_Materials_Guide.pdf

When compared to PVC, PP just doesn't measure up. For proven performance, sustainability and cost effectiveness, PVC is the material of choice for water and wastewater systems.

If you have any questions about the comparison sheet, please feel free to contact us.

  

PVC vs. PP: Not All Thermoplastics Are The Same

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