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.
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.
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.”
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.
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.
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.
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.
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.
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.
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!
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.
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.
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.
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.
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).
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.
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.
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).
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.
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.”
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.
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.
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.
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.
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.
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.
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.