IT IS TIME FOR LEAK FREE WATER SYSTEMS
Steve Grigory, PE
Broken Water Pipes a Ritual of Summer?
According to articles in the Express-News, the San Antonio Water System
(SAWS) tells us that we should expect water main breaks as a summer happening. Similar
breaks have been reported in the paper and on TV for Houston and Ft. Worth. Does
anyone on a water company staff wonder why the gas company does not expect fires and
explosions from similar breaks in gas mains as a seasonal phenomenon? Both utilities use
pipe to transport their product yet one system fails annually from ground movement while
the other rarely leaks unless damaged by contractors digging across the pipeline.
It is painful to see local water companies in the Hill Country
installing PVC pipe with gasket joints (cheap cheap cheap) when it is well known that
these joints will leak. The first thing the water company had to do on our brand new
PVC water mains in our neighborhood was fix the leaks - at least they fixed the big ones
they cold find.. It is a little more expensive up front but there is a better
material for water pipe that saves both money and water in the long run.. This is
important when water utilities lose as much as 30% of the water pumped into the piping
system.
There is a Better Way - Polyethylene
It is possible to have a virtually leak free piping system that will
resist corrosion and ground movement as severe as earthquakes. For over 33 years, gas
companies worldwide have used polyethylene (PE) pipe for new pipelines and are
systematically replacing cast iron and steel pipe with polyethylene. PE pipe is so widely
used in Europe that it is color coded black for sewer pipe, blue for water pipe, and
yellow for gas pipe. (Yellow PE pipe or black PE pipe with yellow stripes is now the color
code of the US gas utility industry while other industries have not accepted color coding
for the safety of construction and maintenance crews). In Japan, PE pipe performed so well
during the last two earthquakes that all steel pipe is being replaced with PE pipe as
rapidly as possible. PE also performed without failure during the last big San Francisco
earthquake. The gas lines that broke and caused the big fires in San Francisco and Japan
were made of metal and fire fighting was hampered by broken metal water mains.
Water Loses are High in Traditional Water Systems
Historically, gas utilities have sought the best materials available to
transport gas because of public safety issues. Water utilities on the other hand have
opted to go low bid with materials with which they are accustom to working,
because water leaks are rarely harmful to the public. As a result water companies
typically lose up to 30% of their product from leaks in the piping system. SAWS admits to
a loss of about 10% from leaks because of an aggressive leak detection program. However,
after recent TV coverage of water main breaks one might question that number.
Also historically, water is thought of as a free commodity. But of
course water is not free. It costs money to pump it out of the ground or treat surface
water to purify it. This economic and ecological loss is passed on
to customers as an operating expense and the lost profit from lost water is never put into
the equation. Today's managers in many companies try to look good by reducing up front
costs without regard to long term consequences because this is what the boss sees as good
performance. It is tragic that making a choice for technically outdated
piping is now wasting water that new pumping restrictions may prevent cities like
San Antonio from having in the future at any cost . Its time we take a serious look
at the future security of the Southwest's water supply by exploring the positive
attributes of polyethylene water piping systems
The city of Bandera, Texas recently confronted replacement
of an aging steel water system that was losing 40% of transported water to leaks. As long
as water companies choose pipe materials that are brittle or that are subject to corrosion
and premature failure, water losses such as those experienced in San Antonio, Houston, Ft.
Worth and Bandera may be expected.
Gas Systems Must Be Leak Tight for Safety
Gas companies periodically inspect 100% of all gas lines for leaks.
City Public Service of San Antonio covers a quarter of their system each year. It is my
understanding that very few leaks are found in neighborhoods with PE gas mains whereas
areas with steel piping keep the repair crews pretty busy. (Keep in mind that the gas
leaks we are taking about are usually so small that they must be detected with
sophisticated instrumentation. Water leaks this small would never be detected much less
repaired. For a more quantitative example of the impact of materials on inspection
frequency consider a large northern utility. The soil freezes and thaws several times each
winter to a depth of several feet. This causes severe soil movement so that in a bad
winter, 100% of the cast iron gas mains are inspected frequently, 100% of the steel
gas mains are inspected several times each winter but most of the PE gas mains are
inspected only once every three years because of their historical infrequency of
leaks.
Polyethylene Pipe is Used In Most Industries That Cannot Tolerate
Leaks
There was a recent article on the color coding of a concrete pipeline
being constructed to carry effluent from the sewage plants in San Antonio to golf courses
for irrigation. Gifford-Hill is adding a lavender color to the cement in the concrete
pipe. Evidently this water is not considered safe for drinking. If there is a need to
distinguish this pipeline from other water lines to prevent a crew from tapping into it
some time in the future, do we not want a leak free line to protect the public and the
Edwards Aquifer? Gifford-Hill is a fine company and they make excellent concrete products.
However, we will let Gifford-Hill tell us why concrete pipe is not used to transport
petroleum products and chemical waste.
 | PE pipe does not corrode.
|
| PE pipe is flexible so that ground movement from swelling and
shrinking soil and even earthquakes will not damage it or cause joints to leak.
|
| (Not much of a problem in the arid Southwest - but a frozen PE water
line will not break)
|
| PE pipe has a smooth interior so that less energy is required to pump
water through it than for concrete or steel.
|
| PE pipe may be heat fused or mechanically joined to make leak tight
joints that will last the life of the pipe.
|
| PE pipe may be squeezed like a water hose to shut off
a leak at the source - this does not damage the pipe in anyway and reduces the number of
valves required in a system.
|
| PE pipe up to 6-inches in diameter is available in
coils of several hundred feet to reduce the number of joints in the pipeline.
|
| PE pipe up to 54-inches in diameter is available in
standard straight lengths.
|
| Several methods are presently being used to replace steel, concrete
and cast iron pipe with PE pipe without digging the trenches that disrupt traffic and make
a mess.
|
| Research that has been conducted at Southwest Research
Institute and Ohio State University indicates that a conservative estimate of the life of
a properly selected, properly installed, PE piping system is at least several hundred
years
|
| Polyethylene is an amazing material
|
Wasting Water Through Leaks Can No Longer Be Tolerated
It is time that water companies in the Hill Country as well as the
large cities in the water precious Southwest considered the installation of a leak free
water distribution system to conserve this precious resource and make other conservation
measures more palatable. How many glasses of water must be refused in restaurants to make
up for the large water main breaks that occur in San Antonio each summer. After
record rains and floods in October of 1998, San Antonio entered another period of drought
and received less than 0.5-inches of rain in the following six months. The Guadalupe
River dried up above Canyon Lake in the Summer of 2000. 
The Plastic Pipe Institute (PPI)
meets twice a year in the spring and fall. The PPI is a technical
trade organization that prepares standards and codes to assure that plastic piping
products and installation methods meet the highest quality standards for the
transportation of all industrial products including gas, water, sewage, petroleum, and
chemicals. PPI and its member companies work with AWWA in the maintenance of AWWA
standards such as C901 and C906.
We would invite engineers and managers from water utility
companies to contact Mr. Rich Gottwald, Executive Director
of PPI and arrange for a seminar on the virtues of PE Pipe. Hopefully they will
learn of the plastic piping alternatives that can provide a long lasting, leak free piping
system to transport a commodity that is becoming increasingly precious to the Hill Country
and all of the Southwest. Visit the PPI
website for more information.
09/25/08
