You may know how important fresh water is to our diet, but did
you ever think about how much water we consume every day? Americans
and Canadians use more water than any other country, even those
that are as equally developed. In fact, a typical family of four
uses about 350 gallons per day at home for drinking, bathing,
clothes and food washing, garden sprinkling, etc. Fortunately,
Americans and Canadians enjoy some of the cleanest and safest
drinking water in the world.
other parts of the world, microorganisms that cause life-threatening
waterborne diseases such as cholera, typhoid and dysentery often
find their way into water supply systems. Diseases associated
with dirty water kill more than 25,000 people per day -- more
than 9 million each year -- around the world, according to the
World Health Organization. Since 1908, however, when chlorine
was first used in New Jersey to purify water, such epidemic diseases
have been virtually wiped out in the U.S. and Canada.
tap water that meets federal and state standards is generally
safe to drink, there are still threats to water quality and quantity.
In fact, the ability to regularly deliver safe water is a constant
challenge to water suppliers. This publication will detail some
of the myriad problems water distribution officials in the U.S.
and Canada face every day, from corroding drinking water pipelines
to the threat of waterborne diseases -- and how they can fix them.
document will first review the types of water pipelines used throughout
the U.S. and Canada, the types of structural problems some of
these pipes experience and the costs which are incurred due to
these structural problems. Because pipeline structural problems
can lead to contamination, this document will also discuss the
increased threat of waterborne diseases. Finally, because chlorine
chemistry plays a major role in safely delivering water to homes,
businesses and schools -- through both disinfection and piping
material -- this paper will show how pipelines made from chlorine-based
vinyl plastic are part of the solution to these water-transport
Use in Different Countries
Pipe Failures Increase Risks
iron, vinyl and reinforced concrete represent the bulk of pipelines
currently being used in the U.S. and Canada to deliver safe drinking
water. However, cast iron and ductile iron distribution pipes
are the most susceptible to corrosion and breakage. In fact, each
year, thousands of water lines are removed for replacement --
most suffering from severe deterioration caused by corrosion.
iron, usually thought of in terms of rust, may take many forms.
In the case of buried iron pipe for drinking water and sewage,
the corroded material is a hard, graphitic substance which temporarily
maintains the shape of the pipe wall and looks like iron, but
provides virtually no strength. Later, the material can form pits,
which, in some cases, penetrate the wall and cause leaks. This
type of corrosion contributes to water loss, pipe breakage and
potential water contamination.
in soil texture, temperature, moisture, oxygen, chemical make-up,
organic material and bacteria are common factors that can contribute
to corrosion and eventually cause pipe failure. The soil environment
itself is a prime cause of iron pipe failures. Officials from
Florida to Ontario have reported that ground conditions weaken
Drought periods followed by heavy rain can cause ground conditions
to become unstable, causing corrosion-embrittled pipelines to
fracture and break. This can ultimately lead to severe water leakage.
The resulting effects include street cave-ins, sinkholes and potholes
-- not to mention wasted water. A single pipe leaking just one
gallon of water per minute, for example, equals more than 500,000
gallons of water loss each year.
problems are ever-present, costly and health-threatening. According
to a recent survey conducted by the Canadian National Research
Council, cast iron pipes are rupturing at a rate of 35.9 breaks
for every 100 kilometers of pipe in service. And newer ductile
iron pipes are averaging about 9.5 breaks per 100 kilometers.
These numbers are significant because they translate into over
200,000 breaks every year in the U.S. and Canada.
terms of cost, taxpayers in Canada spend an average of $82 million
every year to repair broken water mains -- an estimated $2,500
in repair costs alone for each pipe failure. And the Federation
of Canadian Municipalities estimates that they lose about $650
million worth of water every year. The U.S. Environmental Protection
Agency (EPA), after conducting a national survey among U.S. water
systems, recently found that the U.S. will need to invest about
$138 billion to repair the water transportation infrastructure.
According to EPA, the single largest category of need is the replacement
of existing water distribution pipes - about $77 billion.
of Microbial Growth
threat of excessive microbial growth along the interior walls
of drinking water distribution pipes is another health concern
of water distribution officials. Biofouling -- the development
of an organic bacterial community, also commonly known as biofilm
-- is composed of microorganisms and their secretions. It is present
in almost every water distribution system, and when uncontrolled
may present a threat to public health.
are layers of bacteria that attach to the interior walls of water
distribution pipes and to one another -- most heavily around corroded
surfaces on pipes. The bacterial community traps nutrients, microbes,
worms and waterborne pathogens to form an almost impenetrable
material. Almost immediately after attaching itself to pipeline
walls, the organism begins building upon itself, adding layer
upon layer, forming a plaque-like coating. Such growth, together
with tuberculation (corrosion encrustation), can clog water lines
to the point of insufficient water pressure. This becomes a hazard
for homes, businesses and even firefighters. In 1996, for example,
a home that caught fire in Ontario was completely burned because
the water-supply pipes were blocked with buildup, causing insufficient
water pressure to extinguish the fire. In addition, biofilm contributes
to further pipe corrosion and can deplete the chlorine used to
disinfect drinking water and maintain water quality.
proper maintenance, excessive biofilm buildup, which can at times
only be removed by scraping, can cause all sorts of other problems.
During the summer of 1996 in Washington, D.C., and Boston, Mass.,
for instance, water supply officials found E. coli during routine
sampling of the water distribution system, which remained present
for some time after initial corrective measures were taken. D.C.
health officials and EPA representatives cited biofilm as the
primary cause of the contamination, while pledging to systematically
replace or reline aging pipes.
Billions of January '95 Dollars)
the drinking water supply is the method usually used to control
biofilm growth. In most cases, maintaining the normal amount of
chlorine used to disinfect drinking water will control this problem.
However, some water distribution systems, such as those in D.C.
and Boston, have required special cleaning efforts. In both cases,
water officials used remedies such as superchlorination (the process
by which health officials apply increased chlorine levels to eliminate
microbial growth) and/or high-velocity flushing on an intermittent
basis. Depending on the amount of buildup, water suppliers may
increase chlorine levels for a week or so to combat excess levels
inside their water pipes.
cases where the water is nutrient-rich and the biofilm has developed
into a plaque-like coating, officials often have to flush the
system with both increased chlorine levels and large amounts of
water to flush away the biofilm. In extreme situations, officials
implement more costly scouring programs which use mechanical devices,
often referred to as "pigging," to remove biofilm growth.
none of these processes work, some officials suggest replacing
or relining distribution pipes. When it is not necessary to replace
an entire pipeline, contractors may install protective vinyl liners
inside damaged pipes.
Vinyl Pipe Solution
metallic water main materials are prone to rust and scale build-up,
environmental and civil engineers working for municipal water
utilities, sewer utilities and design engineering consulting firms
have made vinyl the most often used pipe material today. On a
linear basis, more vinyl pipe is currently being installed for
buried water pipelines throughout the U.S. and Canada than the
combined total of all alternative pipe materials. This widespread
use is testimony to vinyl pipes' abilities to solve the more serious
problems associated with operating and maintaining buried collection
and distribution pipe networks.
Vinyl pipe, to some degree, is flexible -- a benefit other pipe
materials do not have. This property provides a distinct advantage
when pipes must be laid through unstable, shifting or heaving
soils. Soil fluctuation can wreak havoc on just about anything
in the ground that isn't both flexible and durable (in other words,
immune to corrosion). Vinyl pipes are inherently inert to aggressive
soil conditions and do not need the costly secondary internal
protection found inside metallic pipes. Moreover, studies have
shown that vinyl pipe breakage rates actually decline with age.
In contrast to the much higher failure rates reported for other
pipe materials, the failure rate documented for vinyl water pipes
in Canada was only 0.7 per 100 kilometers of vinyl pipe.
water mains also provide great resistance to biofilm formation.
In fact, vinyl will not deteriorate or break down under attacks
from bacteria or other microorganisms. Vinyl simply will not serve
as a nutrient to bacteria growth the way most alternative pipeline
materials do. And because vinyl pipe surfaces are smoother, water
flows more easily than in metallic or cement-based pipes, enabling
customers to save money on pumping costs.
inherent durability, smoothness and installation ease afforded
by vinyl pipes provide substantial benefits and help explain their
appeal. Immune to both underground external corrosion and internal
pipe corrosion, vinyl pipe can deliver water as clean and pure
as it is received. The expanded use of vinyl pipe and the phasing
out of other materials has the potential to slash annual maintenance
and repair costs by 93 percent or more. And the potential savings
range in the hundreds of millions of dollars per year.
Even with some
of the safest water in the world, much of the water pipe infrastructure
in the US and Canada suffers from serious deterioration. Recent
events -- including waterborne disease outbreaks and extended
"boil-water" notices in major cities -- have focused attention
on the danger associated with contamination of public water supplies.
Water contamination caused by fragile, aging pipelines and biofilm
growth play a major role in water quality, maintenance and service
interruptions, the need for costly infrastructure repairs and
roadway and fire hazards.
vinyl pipes and chlorine are proving to be key solutions to these
expensive, health-threatening problems. Experts agree that chlorine's
introduction early this century into drinking water systems is
one of history's great public health advances. Vinyl -- with chlorine
as a major building block -- is also proving to be an integral
material in safely delivering water. It has increasingly gained
popularity in today's underground water conveyance systems. These
economical, strong, durable and easy to install pipes are giving
water officials confidence that they can safely deliver safe water
to their customers. In short, thanks to chlorine and chlorine-based
vinyl pipes, more and more people are drinking safe water -- delivered
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