A Closer Look at the
Role of Corrosive Soils in Water Main Breaks
The
report by Utah State University's (USU) Buried Structures Laboratory on failure
rates of the most commonly used water pipe materials titled, "Water Main Break
Rates In the USA and Canada: A Comprehensive Study," has received a lot of
attention since it was released in March 2018. The report has been reviewed in
more than 155 countries and cites corrosive soils as a leading contributor in
water main breaks.
Click
here for report.
NACE's Materials Performance
Magazine Reviews Utah State Study
An article by Ben DuBose in Materials Performance titled, "Study Examines
Corrosive Soil Conditions Behind Water Main Breaks," has a closer look at USU's
findings. Materials Performance is the world's largest circulation journal
dedicated exclusively to corrosion prevention and control. It is published by
the National Association of Corrosion Engineers (NACE International).

Below are excerpts from the
article:
Direct Correlation Between Soil
Corrosiveness and Break Rates of Metallic Pipes
Of utilities surveyed, 75% reported operating pipes in one or more soil areas
with moderate or highly corrosive conditions. "Utilities with a higher
percentage of iron pipe may experience a higher percentage of corrosion-related
breaks…This would especially apply to pipe installed without an increased
investment in condition assessment, pipe monitoring, and corrosion control
measures. The study found a direct correlation between soil corrosiveness and
the break rates of metallic pipes."
According to lead researcher Dr. Steven Folkman, a cast iron pipe located in
highly corrosive soil is expected to have over 20 times the break rate of a
similar pipe in low corrosive soil. "Traditionally, the thickness of the iron
pipe wall provided the additional corrosion protection," he writes. "[Cast iron]
pipes manufactured after World War II have significantly higher failure rates
due to thinner walls."
Meanwhile, ductile iron (DI) pipe in highly corrosive soil has over 10 times the
break rate compared to DI pipe installed in mildly corrosive soils. "Because the
wall thickness of [ductile iron] pipe has decreased over time, internal and
external corrosion are a bigger concern for this pipe product," Folkman says.
Corrosion Prevention Methods Used by
Utilities Often Ineffective
The survey found that 80% of respondents reported using at least some form of
corrosion protection. In order, the top five most common preventive methods used
by water main operators are polywrap; anodes or cathodic protection; V-bio
polywrap; impressed current; and dielectric coatings.

However, Folkman cautions that many water utilities often do not know the
specific cause of external corrosion observed on their water mains.
Consequently, the chosen preventive measure may not work effectively. "For
example, it is not effective to install an anode on a main that has a
bacteriological corrosion problem," he says. "Similarly, an anode bag installed
to reduce corrosion caused by a stray impressed current would be quickly used up
and would provide only short-term protection. Also, polywrap does not protect a
pipe from all corrosion types and may get damaged during installation.”
Municipalities Urged to Consider
Using More PVC Pipe Which Has Lowest Failure Rate
Dr. Folkman urges
water main operators to consider using PVC pipe, which had the lowest overall
failure rates in both the 2012 and 2018 USU surveys. "PVC is not subject to
corrosion, unlike ferrous and concrete steel cylinder pipes," he explains.
Folkman says water main operators are gradually moving in the direction of PVC,
with 74% of utilities allowing its use in 2018 - up from 60% in 2012. "A lower
failure rate contributes to a lower total cost of ownership," he says, in
addressing cost concerns.
Regards,
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Bruce Hollands
Executive Director | Uni-Bell PVC Pipe
Association
201 E. John Carpenter Freeway, Suite 750 |
Irving, TX 75062
T. 972.243.3902 ext. 1019 | F. 972.243.3907
www.uni-bell.org
 
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