Water & Wastewater Asia March/April 2019

38 | FROM THE GROUND
Sooner or later, every water distribution
system will leak — both in remote
rural areas as well as dense urban
cities. The consequences of a pipeline
leaking in a forest, forming a small stream
that appears to be part of the natural
surroundings, may not necessarily justify the
need for leak detection systems in remote
areas. However, permanent leak monitoring in
high density areas can reduce the disastrous
impacts of pipe bursts which can trigger a
tsunami of costs far beyond the expense of
the pipeline repair alone.
The key is being prepared to minimise the
costs and complications related to those
leaks. This starts with mapping the utilities
water distribution system using a solid
Geographic Information System (GIS), and
adding important details such as pipelines,
including material, age and burst frequency.
By using a GIS system, the utility can then
develop a plan for managing its pipelines,
which would include pipe rehabilitation, pipe
replacement, pressure management and leak
detection activities.
PREPARE FOR THE INEVITABLE
There are two basic leak-detection
strategies to take — periodic surveys
(ad hoc or scheduled) and permanently
installed monitoring solutions — but a
combination of the two is what works best. A
periodic survey will reveal active leaks, but it
cannot tell exactly how long a leak has been
active. As a result, there is no accurate way
to quantify the volume and subsequent cost
of the water lost. By contrast, a permanently
installed monitoring system can track the
progression of a leak from the moment it
first appears, allowing a utility to allocate
resources based on priority of leak size and
progression speed.
The extent of a survey programme often
depends on the size and scope of the water
utility. Smaller utilities can assess their entire
systems in a matter of days. A larger utility will
typically conduct condition assessments and
periodic surveys on a rolling basis (Figure 1).
This often means that some pipelines are only
surveyed once every year or two.
Surveys are often prioritised around existing
desktop hydraulic simulation models, based
on the oldest sections of infrastructure
(Figure 2), or on zones with the highest
break rates. But this can still lead to teams
surveying hundreds of kilometres to find
just a handful of leaks. With a permanent
monitoring system installed across broad
swaths of the system, utility can use real time
data to direct survey crews and pinpoint leaks
as they form.
A TENUOUS CONNECTION
To demonstrate both how sensitive and
elusive leak detection can be, Brandon
Jacobs, an Echologics ® field project manager
for Mueller Water Products relates a story
from the West Coast U.S. where the utility
was dealing with a variety of water main
breaks and smaller failures, aggravated by
pockets of corrosive soils.
“We detected a water main leak in an area
where an emergency leak repair had been
performed just a few days prior,” Jacobs
recalled. “When we first got there, we had
a tough time pinpointing the leak, because
a home about 30 metres away had a water
heater leak where the constantly spinning
water meter put out a louder sound than the
water main leak.”
Once the homeowner shut off the water
through the meter, the engineer was able to
locate the actual water main leak, but that
was not the end of the story.
“A couple of days later, a repair crew went
out to fix the water main leak we had
pinpointed,” he related. “They excavated
dry dirt with a backhoe down to the point
where they had cleared enough space to
work. A worker went down into the pit as
soon as wet dirt appeared, so he could hand-
Report
Segment
Distance
(ft)
Pipe
Material
Internal
Diameter
(in)
Client Max.
Acceptable
Break Rate
(brks/mile/yr)
Calculated
Break Rate
(brks/mile/yr)
Remaining
Service Life
(yrs)
▼ ▼ ▼ ▼ ▼ ▼
1 345 Spun Cast 8 2.0 0.293 20 to 29
2 565 Spun Cast 8 2.0 0.454 20 to 29
7 622 Spun Cast 8 2.0 0.289 30 to 39
18 343 Spun Cast 6 2.0 0.102 40 to 49
19 487 Spun Cast 6 2.0 0.008 50+
35 605 Spun Cast 6 2.0 0.069 50+
45 523 Spun Cast 6 2.0 0.425 20 to 29
49 489 Spun Cast 6 2.0 0.336 20 to 29
50 684 Spun Cast 6 2.0 0.028 50+
51 577 Spun Cast 8 2.0 0.807 10 to 19
59 323 Spun Cast 6 2.0 0.102 50+
64 301 Spun Cast 8 2.0 0.688 10 to 19
67 337 Spun Cast 8 2.0 0.062 50+
68 411 Spun Cast 10 2.0 0.008 50+
Figure 1. Detailed pipeline assessment surveys generate statistical input that can be used to generate reasonable estimates of remaining service life,
by pipeline segment, to help utilities prioritise pipe replacement schedules
Water & Wastewater Asia • March / April 2019