Stating Their Case_ PVC Vs

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Stating their Case: PVC vs. HDPE

Sharon M. Bueno Feb 01, 2009

PVC and HDPE pipe are inarguably the two most popular pipes used in underground construction. In a

Trenchless Technology survey published in our August issue in 2008, we polled sewer system

operators and consulting engineers from around the United States about their pipe choices. The

results showed that HDPE and PVC finished either #1 or #2 in most categories. Both types of pipe have

their strengths and weaknesses and appeal to many contractors and project owners due to their

expansive reach in applications. We wanted to know more so we contacted their respective pipe

associations for more information. Interim Uni-Bell PVC Pipe Association executive director Michael

Luckenbill and Plastic Pipe Institute executive director Tony Radoszewski were kind enough to respond

to our questions.

1. Tell us about PPI/Uni-Bell PVC Pipe Association.

Michael Luckenbill: Uni-Bell is the not-for-profit, technical support, t rade

association of major PVC pipe producers and is staffed with engineers whoare knowledgeable in buried pipe applications and design. As a result of the

pipes superior performance and lower maintenance sustainability, the use of

PVC pipes for buried water distribution and wastewater collection systems

has grown steadily, if not remarkably, since their introduction in North America

in the 1950s. Today PVC pipes dominate new installations of both water and

sewer pipes, exceeding the combined total lengths of all alternative pipe

materials combined.

Tony Radoszewski: Founded in 1950, the mission of the Plastics Pipe

Institute is to promote plastics as the material of choice for piping applications.

The primary objective of PPI is to provide a forum for our member companies

to work in a cooperative effort to broaden the market for plastic pipe and

related products.

We are comprised of nearly 140 companies that either make the plastic raw

material or the finished plastic pipe and fittings from those materials. We also have members that makeequipment to process resin into pipe and fittings or help to connect and install plastic pipe. We also have

professional members and related associations as members.

Since our members products serve virtually every underground utility and application where pipe is used, we

have structured our organization into five divisions: Fuel Gas, which focuses on the natural gas distribution

industry; Municipal and Industrial, which focuses on potable water and sanitary sewer (thats the municipal side)

and all other industrial applications which can include mining, landfill, geothermal, oil and gas gathering to name a

few; Cor rugated Pipe, which covers stormwater systems, storm water management including retention and

detention systems, sub-surface drainage and agricultural drainage for maximum crop production; Conduit, which

serves the power and telecommunications industries for underground service lines; Heating and Plumbing, which

covers radiant heating systems and indoor residential plumbing including hot and cold water lines.

Perhaps the most important role the members of PPI play is that of working with industry, government and

educational groups to develop industry standards for pipe and fittings. For nearly five decades, the PPI has and

continues to work with these groups in an effort to engage the standards community in creating open criteria and

test methods that provide the specifier and end user with the most up to date t echnical information possible. We

believe the presence of these industry standards provides assurance that the technologies and processes

developed in the plastics pipe industry are p roven and reliable.

In this effort, we have established long-term relationships with various organizations including the American

Association of State Highway Transportation Officials (AASHTO), the American Society for Testing and Mater ials

(ASTM International), the American Water Works Association (AWWA), American Gas Association (AGA), t he

International Organization for Standardization (ISO), American Society of Mechanical Engineers (AMSE), and the

Canadian Standards Association (CSA). We are also involved with state and federal departments o f

transportation, the Environmental Protection Agency (EPA), the Federal Highway Association (FHwA), various

water c ouncils and we sponsor research w ith multiple state universities across North America.

While many of our member companies have high-density polyethylene (HDPE) interests, our organization also

includes a number of producers of other plastic materials and pipe including polyvinylchloride (PVC), chlorinated

polyvinylchloride (CPVC), polyamide nylon, polypropylene and crosslinked polyethylene. In addition, a growing

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number of our members also have divisions that produce and/or distribute ductile iron, cast iron, steel, copper,

clay, corrugated steel, and concrete pipe.

2. What questions do you commonly hear from people who are shopping for new pipe?

What are they looking for? How do address them?

TR: In the past, the most important question asked was How much? But w ith a growing concern relating to

sustainability, two more questions are becoming equal in importance to the economics of the job: Firstly, what is

the environmental impact and performance of the pipe and secondly, does it create green jobs. More and more

the specifiers for pipe systems are embracing an attitude of environmental stewardship that is driven by a

greater apprec iation of the carbon footprint any pipe system leaves and how well does the pipe line protect and

preserve natural resources. HDPE pipe fits this need exceptionally well.

HDPE pipe has a relatively small carbon

footprint when compared to ir on and

concrete pipe. A study conducted in the

late 1990s concluded that plastic pipe used

in the building, construction and

transportation industries required 56,500

trillion fewer BTUs than iron and

concrete/aggregate alternatives.

With its lower weight per foot, HDPE pipe

is also less costly to transport to the job

site than metal or concrete. And with the

ability to nest smaller diameter pipe in

larger pipe, more feet per truckload can be

delivered with out breeching highway

weight limitations.

In HDPE pressure pipe systems, the fused

joint creates a t otally leak free system.

This means precious natural resources are saved and the energy to treat, store and distribute water is reduced.

For municipal storm water systems, improvements in joint design in corrugated HDPE pipe deliver a water tight

joint that equals and exceeds the performance levels of sanitary sewer systems. This means infiltration or

exfiltration that can prematurely end a storm w ater system or cause road damage due to sink holes, is

dramatically decreased.

When it comes to long-term sustainability, HDPE pipe truly shows its key benefits: it doesnt rust, its highly

resistant to mineral tuberculation and its abrasion resistance is significantly greater than metal, concrete and

other plastics. With todays crumbling underground infrastructure experiencing nearly 700 water main breaks per

day (might want to sight a reference for this number), the need to replace old technology becomes evermore

important.

ML: With ever increasing numbers of pipe failures and their associated high costs, replacing them with the same

or similar pipe materials simply does not make sense. Progressive water and sewer utilities want alternatives

that will last longer and perform better with minimal or no maintenance. In excess of 2 million miles of installed

PVC water and wastewater pipes have demonstrated success in meeting those noble objectives throughout

North America and have rewarded those utilities with substantial cost savings.

Reluctance on the part of some utilities to allow PVC pipe is t he result of commercially tainted miss-information

combined with a general lack of formal training in plastics materials. Admittedly, many plastics are too weak or

too soft for buried pipe applications. From the beginning, the PVC pipe industry has had to invest heavily in

performance testing and research in order to dispel the concerns and educate utilities along with their engineers.

Does the pipe material have sufficient long-term tensile strength and stiffness? Is the pipe material resistant to

permeation in contaminated soils/groundwater? Are the joints water tight? How long can the pipe be expected to

last/perform? Will the pipe corrode or otherwise oxidize? Will sunlight damage the pipe? Can the pipe be used

with conventional appurtenances, valves, fittings, and other connections? How can I locate the pipe after burial?

Over the past five decades, the PVC pipe industry and Uni-Bell have amassed technically correct answers to

these questions and more.

3. How important are pipe materials as part of the purchasing decision?

ML: The efficiency and effectiveness of water and wastewater pipe systems

has a significant impact on the environment, public health and local utility

budgets. The direct costs of corrosion for water and wastewater pipe

systems are $36 billion annually in the United States and pipe corrosion

represents a significant loss in value of the infrastructure investment made by

local governments all across our nation. Furthermore, in the United States we

average 700 water main breaks per day and lose 2.2 trillion gals of treated

water every year, largely due to breaks and leaks. Through the thoughtful

selection of pipe materials that are inherently best suited for the anticipated

operating conditions and environment, literally billions of dollars are being

saved.


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TR: The choice of pipe material for any application, whether underground or

aboveground, can be the most important decision of the entire project many

times surpassing cost concerns. Based on the service the pipe sees or the

ground conditions in which it is installed, the choice of material will dictate the

service life of the system. What affect will the flow have on the pipe material? Is it highly acidic or alkaline? Is it

abrasive in nature? What about the soil conditions? Hot soils can immediately begin to attack the exterior

surface of the pipe. And what about soil contaminants? In any of these instances, a material that is highly

resistant to these conditions must be employed.

Next, one needs to understand the installation methods planning to be used; trenchless or open cut? With HDPE

pipes fused joint, a monolithic pipe string is created allowing for long pulls and minimal surface (and traffic)

disruption.

And lastly, w hat is the lifetime cost of the system? Will special corrosion protection be needed? Will the pipe

have the same flow c haracteristics in 10, 50 or 75 years? What is the anticipated cost of w ater (or other fluid)

loss through mechanical joints? What will be the affect of soil infiltration on road ways w hose cost to repair far

exceeds the cost of the pipe?

4. With so many choices available, what are the key factors a buyer should consider

when buying pipe?

TR: Sustainability, service life, and lifetime costs this is the triple bottom line that todays design engineer

needs to address. Is it the best choice for the environment in terms of energy costs (carbon footpr int) and

protection for natural resources? Is it going to last for multiple generations and then some? What is the total

economic cost, including manufacturing, delivery, installation, operation, maintenance and performance for the

owner/operator? HDPE pipe, both pressure and gravity flow, has proven itself around the world as the best

material choice for water, sanitary sewer, storm sewer, natural gas distribution, mining, oil & gas gathering,drainage, buried conduit, outfall lines, and now even safety systems for nuclear power plants. Its inherent

resistance to rust and abrasion along with the best joint in both pressure and gravity flow applications has made

HDPE pipe the one plastic material used in all underground utilities.

ML: The first and foremost pipe material selection factor is inherent compatibility. Materials w hose long-life

performance depends upon linings, coatings, wrappings or cathodic protection should only be used where

alternatives are not available. I t is f ar better and more sustainable to use pipes that are inherently well suited for

their operating environments, including exposures to contaminated soils. This has contributed greatly to PVC

pipes rise to become the most-installed product for new water and wastewate r systems. Utilities have acquired

a true appreciation of PVC pipes low-maintenance, corrosion-free performance and resistance to permeation by

hydrocarbons at levels normally encountered.

The next important selection factor is strength. Without sufficient pressure capacity and pipe stiffness, optimal

long-lived sustainability will be compromised. Pipe wall thickness design must be sufficient to handle all internal

and external loadings. This requires proper understanding of a pipe materials long-term tensile strength and

long-term stiffness (modulus of elasticity). In addition, all anticipated loads and stresses must be taken into

account. Prudent pipe designs always incorporate an ample safety factor (typically at least 2.0), because

unanticipated installation and operation stresses can occur over the life of any pipe.

Lastly, installation and installation costs are selection factors. The t ype or method of installation may preclude the

use of some pipe products and/or joint types. This is certainly true for trenchless installations.

5. In a Trenchless Technology survey published in August 2008, PVC and HDPE were the

top choices in pipe selections in various categories. Why are PVC and HDPE popular

choices for trenchless applications?

ML: The popularity of PVC and HDPE stems from the f irst selection factor these materials are inherently well

suited for buried wastewater and water pipe applications. Both are easy to w ork with and install. However, it is

important to recognize that PVC and HDPE are not the same. HDPE is a softer, more bendable plastic, making

HDPE pipe more suitable for lower pressure, tight bending radius situations. On the other hand, PVC is a much

stronger and stiffer material, which is why PVC pipes are more widely used for direct burial and trenchlessinstallations. PVC pipes require longer bending radii, but also considerably less material to achieve or meet

desired strength levels. PVC pipes are stiff enough to permit their direct connection to mechanical valves,

non-plastic fittings and various other water and wastewater appurtenances. HDPE pipes are softer and require

stiffening rings or other adapters in order to make proper connections. A recent AwwaRF-funded study has

confirmed that PVC pipes are resistant to gasoline permeation, as w ell as permeation by other generally known

hydrocarbon contaminants at concentrations normally encountered. All of these factors affect the selection and

popularity of PVC and HDPE pipes.

TR: Because of its flexibility and durability, HDPE pipe has been the material of choice for trenchless installation

practices almost since the technology first appeared in the mid- to late-1960s. Furthermore, since a fused joint

produces a monolithic pipe string, the ability to pull long lengths and use all trenchless installation practices

including HDD, sliplining and pipe bursting favors the use of HDPE pipe. Since HDPE pipe has enjoyed such a

long acceptance in trenchless applications, there has been significant research and studies to provide the design

engineer and contractor confidence in application and installation. As an example, there are several documents


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available for the design and installation of polyethylene pipe by directional drilling. The first document is an ASCE

Manual of Practice (108). Another is ASTM standard F1962, which gives detailed design formulas (including

acknowledgement of the fused joint) for a directional drill with polyethylene pipe. The Plastics Pipe Institutes

Handbook of PE Pipe also contains multiple chapters on directional drilling and sliplining and the second edition of

the PPI handbook, which will be published in February, will include a full chapter on pipe bursting.

Another fundamental reason why HDPE pipe is so widely prefe rred for trenchless applications is that it has the

strength to handle this demanding installation practice. Since HDPE pipe is extremely tough it can withstand the

rigorous trenchless installation process and is not affected by scratches and gouges (10 percent of the pipe wall)

that are certain to occur. Other materials are more sensitive to this type of damage which will cause premature

failure of the piping system. HDPE pipes have the physical properties to handle large pulls.

6. Briefly discuss the background and evolution of plastic pipe.

TR: With the invention of HDPE in the 1950s, many industries looked to this revolutionary material to see if it

could improve the performance and economics of currently used materials. The pipe industry was no different.

Although one of its first uses as a pipe material was in oil and gas gathering systems in the oil patch, its first

use in underground utilities occurred in the natural gas distribution market.

Gas utilities were facing an ever-growing number of failures due to corroding steel pipelines. Recognizing the

safety threat of leaking gas lines, the gas utilities looked for a material that wouldnt rust and wouldnt leak at the

joints. Flexible, non-rusting HDPE pipe, with its fused joint filled the void perfectly. Today, 95 percent of gas

distribution systems in North America use HDPE pipe accounting for more than 100 million miles of pipe.

In the mid-1960s, corrugated HDPE pipe was introduced in the agricultural drainage market to replace clay

drainage tiles. Within 10 years, HDPE pipe became the material of choice. In the late 1980s w ith the

introduction of a smooth interior liner, corrugated HDPE pipe became a formidable competitor to corrugated steel

and reinforced concrete pipe in storm water applications.

Today, solid wall HDPE pipe is available in diameters ranging

from to 63 in.; corrugated HDPE pipe is available in

diameters ranging from 1 in. t o 60 inch. HDPE pipe, because

of its inherent physical properties, is used in virtually all

underground utilities.

ML: Industrial PVC pipe production dates back t o the 1930s

in the Bitterfeld-Wolfen chemical industry area of Germany.

Many of those earliest potable water pipes remain in

service. A series of tests on some of those early PVC pipes

has been carried out, and the results compared quite well

against the current norms. This confirmation of long-term performance provides important documentation

regarding PVC pipes sustainability.

PVC pipe technology was brought to North America following World War II, and started to take off af ter the

National Sanitation Foundation (NSF) began studying plastic pipe products for water supplies in 1952. NSFcertification began in 1965. ASTM began publishing standards for PVC water and wastewater pipes in the

1960s.

In 1975, the American Water Works Association (AWWA) approved its very first plastic pipe standard AWWA

C900, Standard for Polyvinyl Chloride (PVC) Pressure Pipe, 4 inch through 12 inch, for Water. PVC has grow n

to be the largest volume plastic pipe material in North America with annual sales in excess of 7.0 billion lbs. PVC

pipe diameters range from 0.5to 48 in.

7. How have buying patterns changed over the years?

TR: Its not so much that buying patterns have changed; rather the mindset in the design community has

changed. Designers and owners recognize they cant continue to operate in the same old way. Although they are

still looking for the best product for the application, newer materials and installation practices are giving them

greater choices than ever before. With more and more information becoming available and continuous

improvement in plastic pipes, older, tr aditional materials such as iron and concrete are giving way to newer

construction materials. Designers are also becoming more focused on the environment and taking particular

interest in preserving natural resources for a growing country. Sustainability and a desire to conserve energy in

every quarter also lend a favorable light to HDPE pipe.

ML: Ever mounting numbers of satisf ied water and wastewate r customers have kept those as the two primary

end-use markets for buried PVC pipes. PVC pipes now also dominate the budding market for reclaimed water

pipe. The acceptance and availability of larger PVC pipe diameters has resulted in a t rend toward t he increased

use of larger pipes.

8. What innovations or changes have occurred with your products recently? What future

changes are in store?

ML: Technological advances in manufacturing process controls and monitoring, together with equipment

enhancements, have enabled PVC pipe product performance and consistency to improve. This progress has


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been steady and evolutionary, not revolutionary.

The development of several innovative joint designs has enabled PVC pipe producers to offer a variety of PVC

pipe options that are very w ell suited for tr enchless pipe situations. The same properties that have made PVC

the market leader among pipe materials for water and sewer applications in North America make PVC a

preferred material choice in trenchless applications. There are four trenchless technology methods for w hich PVC

pipes are extremely well suited. These are Horizontal Directional Drilling (HDD), Sliplining, Tight Fit Structural

Liner and Pipebursting.

TR: One hallmark of the HDPE industry overall, and the HDPE pipe industry in particular is the constant effort to

improve base resins and pipe design. From a materials standpoint, the most recent innovation has been the

introduction and recognition of high-performance HDPE resins fo r pressure pipe allocations, specifically PE 4710.

These resins are not the same old materials with a new name. These are new technology HDPE materials - third

or even fourth generation with performance capabilities surpassing previous grades. Even though the previous

grades of PE materials have an excellent performance history in gas and water service, the HDPE industry

continues to challenge itself the same is not readily noticeable with other base materials and pipes. These new

resins take performance to another level allowing them to be used with higher design stresses without sacrificing

safety or design life.

HDPE resin and pipe have superior resistance to failure and rapid crack propagation (RCP). These are essential

properties for HDD applications where scratching and gouging of the pipe are a fact of life. HDPE pipe can be

gouged up to 10 percent (studies have shown even 20 percent) of t he wall thickness with no detrimental effects

to the long-term performance of the pipe. Resistance to RCP means that the monolithic piping system of heat

fused HDPE pipe will not be susceptible to rapid cracking that can run for hundreds or even thousands of feet

with catastrophic results.

Continued improvements in pipe design, specifically in the corrugated

drainage pipe industry (storm water management) has allowed for greaterburial depths and improved joint performance. Todays HDPE corrugated pipe

is significantly better than the original product first introduced in the

mid-1960s. State and federal Departments of Transportations, municipalities

and private enterprises are the beneficiaries of these efforts.

As technologies in the petrochemical market continue to develop, the

underground utilities industry can expect continuing improvement. This of

course begs the question: What has the metal and concrete industries done

to improve their products?

9. What are some of the common misconceptions regarding

your pipe material? How do you dispel this?

ML: The utilities that are not yet using PVC pipe usually cite insufficient

strength and/or stiffness. The facts are t hat PVC pipes come in a full range of pressure ratings/classes and

stiffnesses. While the minimum pipe stiffness of 46 lbs/in./in. for standard strength PVC gravity sewer pipes has

proven to be good for burial depths in excess of 40 ft, PVC pipes are available with pipe stiffness values up to

1,019 lbs/in./in. The embedment requirements for PVC water pipe are no different than those for ductile iron

pipe. Likewise, while most pressurized water systems operate within a 60- to 120-psi range, PVC pipe pressure

ratings/classes go up to 305 psi; w ith short-term burst pressure minimums as high as 985 psi. Clearly PVC pipes

afford more than sufficient strength to handle the full range of sewer and water sys tem operating conditions.

Some utilities are concerned about soil contaminants permeating through plastic water pipes and associated

human health risks. The fact is that PVC pipes provide a barr ier to permeation and are not penetrated at

contamination concentrations normally found. This PVC pipe benefit/protection was recently confirmed in a

research published by AwwaRF. The AWWA Research Foundation study (published in early 2008) determined

that PVC has superior hydrocarbon permeation resistance to gasoline and BTEXs in both laboratory and field

study conditions.

TR: That HDPE pipe is not as strong or durable as pipe made from steel or concrete is a common

misconception. Of course this is not the case. HDPE pipe is a truly engineered product designed for specific

purposes and long service life. In fact, it has been our experience that when traditional materials cannot handle a

specific application either due to aggressive flows, soils or other unique conditions or installation practices

demand trenchless techniques, HDPE pipe gets the nod. Our biggest f rustration is that we get the most

challenging applications but not the bread-and-butter uses such as potable water, sanitary sewer and storm

water management applications.

We recognize HDPE pipe, although it has been used for nearly 50 years in the gas industry and more than 40

years in storm water management systems, is a new kid on the block, and we have to continually educate and

promote our products to the design and specification community. As a result, our f irst step is to create a greater

awareness to the features and benefits of HDPE pipe. We c ontinue to conduct research, give educational

seminars and promote case studies that verify the broad applications HDPE pipe enjoys. Secondly, we have to

work on gaining approval by the design and specifying firms and agencies to allow engineers to employ our

products. Lastly, the end user or owner will accept the product only when they are confident it is the best product

for their specific application or need.


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10. What is your pipe materials strongest characteristic?

TR: HDPE pipe, in our opinion, is the best product for developing a truly sustainable infrastructure. From its low

energy cost to produce, ship and install, to its superior joint performance in all applications, to it s resistance to

rust and abrasion and finally its short and long term economic advantages, we believe there is no other material

that approaches the performance and versatility of HDPE pipe.

ML: PVC pipe combines the ageless durability that comes with a corrosion-free material w ith the overall strength

and stiffness required to handle both water and sewer system demands at a cost t hat is comparable or less than

the alternatives. PVC is arguably the most sustainable and cost-effective of all pipe mater ials.

11. How does increasing the awareness and importance of pipe materials help theconsumer?

ML: Consumers need to know that there are options when it

comes to pipe materials and products. Moreover, within a

given material such as PVC, a broad range of product

strengths exists that allow f or cost-efficient design for

almost any situation. Single product or material

specifications should be the rare exception and not the rule

given these options. As the No. 1 water and wastewater

pipe material, most utilities across the country have come to

appreciate the installation and operation benefits that PVC

pipes and fittings provide.

TR: Nobody gets fired for buying IBM, is an old saying that basically translates to: Dont take a risk. Design

engineers take on an awesome responsibility, much like the Hippocratic Oath of doctors to First, do no harm.

Recognizing this, we are obligated to provide the highest level of information to ensure engineers, specifiers, city

officials and end users all know the performance levels of our products. As good as HDPE pipe is, it can not do

everything. With the American people becoming keenly aware of everyones responsibility to be good s tewards

of the planet and that our underground infrastructure is in need of hundreds of billions of dollars in repairs to

ensure we have safe, clean water and gas coming to our homes, plastics can and will be leading the charge.

HDPE pipe offers low lifecycle costs, high sustainability and the best perfo rmance attributes. It makes no sense

to keep doing the same thing that was done 100 years ago and education is the key to make this change.

Sharon M. Buenois managing editor of Trenchless Technology.

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