- ByProf S S Jahagirdar
How much is Acceptable?
If Water loss is
1. 5 to 7 % then it is acceptable
2. 10 to 20 % then it is unsatisfactory :action is advisable
3. Beyond 20% :- remedial measure
must be immediately taken
Causes of leakage in mains
Fixtures in consumers premises – faulty
washers, valves and taps, not closing the
taps knowingly or unknowingly
Usually, wastages from reservoirs
cannot be accounted for metering
Leakage can lead to:
—consumer inconvenience , by
reducing pressure at taps, appliances
and showers, etc.;
—damage to infrastructure , by creating
voids which can lead to collapse of
highways and buildings;
—increased loading on sewers due to
infiltration, leading to the need to
over-design sewer capacity;
—excessive costs, not only from
compensation payments and from
repairs to damaged structures, but also
production costs (if leakage is 50% of
production, energy and treatment costs
have been doubled);
—introduction of air into the
distribution network if the water
supply is intermittent, causing damage
to meters, and leading to overmeasurement of the true consumption
and errors in water bills;
—health risks, in low pressure systems or
where the supply is intermittent, by
allowing infiltration of sewage and
other pollutants into the pipe network.
Poor quality materials and
Leakage control method
The water losses can be termed into
1. Physical losses (Technical or real
2. Non-physical losses (Non-technical
losses/Commercial or apparent
This is mainly due to leakage of
water in the net work and
comprises of physical losses
from pipes, joints & fittings,
reservoirs & overflows of
reservoirs & sumps.
Non Physical Losses
- Theft of water through illegal, already
- under-billing either deliberately or
through defective meters,
- water wasted by consumer through
open or leaky taps,
- errors in estimating flat rate
- public stand posts and hydrants
The objective of water audit is to assess the
i) Water produced,
ii) Water used,
iii) Losses both physical and non-physical,
iv) To identify and priorities areas which
need immediate attention for control.
Leakage detection methods
1. By visual inspection
2. By using sounding rods or
3. electronic leak detectors or
4. using radioactive isotopes etc
5. By plotting Hydraulic Gradient Lines
Walking over the main looking for
signs of presence of stagnant water
Stagnant water presence depends
upon soil characteristics.
Many times difficult to find out
exact location of leak,
2. Sounding rod
The sound made by water leaking from a
pipe is the basis for the majority of leak
Under traditional sounding air inspector
uses the simplest instrument for leak
detection a listening rod or the sounding
This is prepared from a 12 mm light
steel rod of 1.2 to 1.5 m long. At the top
of the rod a brass bowl of 25 mm is
To locate the exact leaky point the rod
is moved on the ground surface along
the center line of the alignment of the
buried pipeline, by keeping the ear on
the top of the rod.
The vibration due to the leak is picked
by the sounding rod and converted into
sound and is heard by human ear.
The sound emitted by a leak is a ‘low
drumming noise’ or ‘continuous
buzzing sound’ and tends to be
continuous without any change of
audibility or quality.
It stops abruptly when and if, the water can
be turned off. Thus locating the possible
leak is identified.
Sounding should be done at night when
the background noise is low. It is
absolutely necessary that the persons be
trained properly in using this technique.
3. The theory of Water Leak Detection
using acoustics: using ground microphone
When a pressurized water pipe develops
a leak the water flows out into the
surrounding ground at high speed,
which causes the pipe and soil to vibrate
at the exit point.
This sound, or vibration, is transmitted
by the pipe, (structure borne) and
surrounding material (ground borne)
where it can be heard with the highly
Electronic leak detector consists of a
ground microphone, amplifier and
The electronic leak detector is sensitive
and can pinpoint the position of the
Modern electronic leak detection
devices permit discrete filtering of many
background sounds that compete with
the sound of leak itself.
4. Beta Radiation in Leak Detection
Leaks in underground pipelines can be
detected by the injection of a radioactive
This is achieved by adding a small amount
of a radioisotope which is a source of beta
radiation to the fluid.
The area above ground where a high
intensity of beta radiation is detected will
pin point the leak source in the pipeline.
This saves time as the correct area is dug up.
It is important to use a radioisotope
with a half life of a few hours or days.
This is so it remains long enough for
the leak to be detected but not too long
that it may pose a safety or health risk.
Sodium 24 is an example of a
radioisotope used in leak detection. It
has a half life of about 15 hours and
emits beta radiation along with gamma
5. By plotting hydraulic gradient
In this method , the pressures at
various points of suspected pipe line
Hydraulic gradient line is plotted.
The appearance of any change in slope
of hydraulic gradient line indicates the
location of leak in the pipe line
Maintainace should include
1. Periodical inspection of source, intake,
treatment plant units, storage reservoirs,
pipes, valves, meters, connections etc.
2. Flushing (Cleaning) of pipes by
3. Replacing the damaged pipes before life
4. Speedy and quality repairs of
joints, valves and pipes
5.Regular Water quality monitoring.
6. Proper leak detection and
7. Keeping check on unauthorised
8. Carrying out water audit
9. Pressure management in the
Advantages of Pressurized water
i. Sufficient head will be available
even during peak demands.
ii. In case of fire break out water will be
available in sufficient quantity and
iii.Less possibility of wastewater entry
and contamination as flow is full
and under pressure.
iv. No possibility of accumulation of
solids within the pipe network
v. Infiltration is not possible easily.
vi. saving pumping cost at user ends.
Variation in water quality in
Improper design and operation may result
in water of diminished quality in terms of
increased water age, reduced
disinfectant residual, increased growth
of disinfectant by-products and
bacterial levels, and may impact the
level of compliance with current and
impending water-quality regulations
Q1. Enlist various leak detection methods
and explain any two in detail
Q2. Write short note on
1. Sounding rod for leak detection
2. Advantages of Pressurized water
3. Maintenance of water distribution system