| Water Pipelines: "..... what is
certain is that cholera was carried by rusty old and leaking water pipes
that run through gutters all over the city.......the entire pipe network dates back to
World War II........... "
from a news article "Cholera surfaces in Bombay" published on www.rediff.com
The above comments are a poignant illustration of serious problems that can occur in
aging, degraded water pipeline systems. There are numerous examples of similar scenarios
in many parts of the world.....and large-scale leaking is by no means limited to
developing countries (link to Facts&Figures).
Click on image to enlarge
Image courtsey of PPT, Pipeline Performance Technologies, South Africa
| Aging water pipelines tend to rupture at a rate
of 35.9 breaks each year for every 100 kilometers. For newer pipelines the rate is more
than three times lower. Corrosion damage (internal and external) is recognized as a major
mechanism contributing to pipeline breaks. Source: Chlorine Chemistry Council
(http://c3.org) |
| Aging water mains have been reported
to leak at rates of 150-300 l/hr/km with newer mains
having lower leak rates of 100-200 l/hr/km. Source:
A.C. Twort, F.M. Law, F.W. Crowley and D.D. Ratnayaka: "Water Supply", Fourth
Edition, Arnold, 1994. |
The graph below illustrates estimated water leak rates from
pipelines as a function of the pipe perforation area ("hole size"), at two
different operating pressures.
Click on graphics to enlarge (metric version on r.h.s.)
This simple estimation model is based on a formula presented in the
following publication: The Texas Water Development Board: "A Guidebook for
Reducing Unaccounted-for Water", Revised August 1999 (TWDB GB-2 91-0504).
Potential negative effects of corroded, leaking
water distribution pipelines include the following:
- Increased risk of contaminating the water supply and resulting disease.
- Impaired water quality (e.g. "red" (rusty) water from internal corrosion).
- Reduced hydraulic capacity (internal corrosion products and surface deposits).
- Increased cost and effort of water treatment.
- Isolation of a leak location for repair operations can lead to increased pressure in
other parts of the systems, with possible additional costly leaks resulting from the
rising pressure, especially in aging systems.
- Loss of water after costs for its procurement, treatment and pressurization have already
been incurred.
- Lost revenue for system operators.
- Higher costs for system users.
- Water "vulnerability" and shortage.
- Property damage (for example, sink holes and flooding have resulted from water leaks).
- Exposure to litigation.
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