Environmental Engineering-I (Water Supply Engg.) - TE (CIVIL) Course material by PROF S S JAHAGIRDAR, NKOCET, SOLAPUR.

6. Environmental Engineering-I
- ByProf S S Jahagirdar

7. 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

8. Causes of leakage in mains
 Corrosion
 Cracks
 Faulty joints
 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

9. Types of leakages

13.  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;

14. —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;

15. —health risks, in low pressure systems or
where the supply is intermittent, by
allowing infiltration of sewage and
other pollutants into the pipe network.

17. Pressure
Soil movement
Pipe condition
Poor quality materials and
workmanship
Soil characteristics
Traffic loading
Leakage control method

19. The water losses can be termed into
two categories.
1. Physical losses (Technical or real
losses)
2. Non-physical losses (Non-technical
losses/Commercial or apparent
losses).

20. Physical Losses
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.

21. Non Physical Losses
- Theft of water through illegal, already
disconnected connections,
- under-billing either deliberately or
through defective meters,
- water wasted by consumer through
open or leaky taps,
- errors in estimating flat rate
consumption,
- public stand posts and hydrants

23. Water Audit
 The objective of water audit is to assess the
following.
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.

24. Fixing bulk meters

25. 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

26. 1.Visual inspection
Walking over the main looking for
signs of presence of stagnant water
over ground.
Stagnant water presence depends
upon soil characteristics.
Many times difficult to find out
exact location of leak,

27. 2. Sounding rod
 The sound made by water leaking from a
pipe is the basis for the majority of leak
locating techniques.
 Under traditional sounding air inspector
uses the simplest instrument for leak
detection a listening rod or the sounding
rod.
 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
fixed.

28. 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.

30.  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.

31. 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
sensitive microphones.

32.  Electronic leak detector consists of a
ground microphone, amplifier and
headphone.
 The electronic leak detector is sensitive
and can pinpoint the position of the
leaks.
 Modern electronic leak detection
devices permit discrete filtering of many
background sounds that compete with
the sound of leak itself.

34. Ground Microphone

36. 4. Beta Radiation in Leak Detection
 Leaks in underground pipelines can be
detected by the injection of a radioactive
isotope.
 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.

37. Use of radioactive isotopes
Sodium 24

38. 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
radiation.

39. 5. By plotting hydraulic gradient
lines
 In this method , the pressures at
various points of suspected pipe line
are measured.
 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

41. Maintainace
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
- Water
- Air
- Swabbing
3. Replacing the damaged pipes before life
span

42. 4. Speedy and quality repairs of
joints, valves and pipes
5.Regular Water quality monitoring.
6. Proper leak detection and
management system
7. Keeping check on unauthorised
connections
8. Carrying out water audit
9. Pressure management in the
system

43. Advantages of Pressurized water
supply
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
pressure.
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

44. v. Infiltration is not possible easily.
vi. saving pumping cost at user ends.

45. Variation in water quality in
distribution system
 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

46. Theory questions
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
distribution systems
3. Maintenance of water distribution system