This document summarizes a lecture on water supply and waste water management. It discusses factors that affect water consumption such as climate, population characteristics, metering and conservation programs. It also outlines average daily water consumption for different purposes including domestic, commercial, industrial and public use. Fire demand is calculated using formulas from the Insurance Services Office and National Board of Fire Underwriters. Numerical problems demonstrate calculating water demand for buildings and residential areas including fire demand.

1. CT-207 water supply and waste water Management
Lecture# 03
(4th semester civil)
By: Engr. Hayat Hussain
Lecturer Saidu polytechnic institute saidu sharif Swat

2. Content
❖Water consumption
❖Factors affecting water consumption
❖Water demands for different purposes
❖Average daily consumption
❖Fire demand
❖Numerical problems

3. ❖Water consumption for different purposes
The various types of demands are:
a) Domestic: water uses are for drinking, cooking, meeting of sanitary
needs, irrigating lawns. Residential water use rate fluctuates regularly.
Average winter consumption is less than the annual daily average, where's
in summer consumption average are greater. Similarly peak hourly
demand is higher than max.no universally applied rule for prediction.
b) Commercial & industrial: it includes factories, offices and commercial
places demand. It is based on either having separate or combined water
supply system. Demands of water based on unit production, numbers of
person working and floor area.
c) Public use: schools, hospitals, fire fighting etc.
d) Losses and wastes: unauthorized connections leakage in distribution
system, hydrant flushing, major line breakage and cleaning streets and
irrigating lawns.
Total consumption= a+b+c+d

4. ❖Factors affecting water consumption
1. Size of city
2. Industry and commerce
3. Characteristics of population
4. Metering of water
5. Climate
6. Quality
7. Pressure
8. Maintenance system
9. Conservation programmes

5. 1. Size of city
Size of city has indirect effect in that small communities tends to have
most limited use for water. On other hand, the presence of an important
water using industry may result in high per capita use. Small
communities are more likely to contain areas which are inadequate
served by both water and sewerage system.

6. 2. Industry and commerce
Industries have a pronounced effect upon the total consumption. Since
industrial use have no direct relation to population, great care must be
taken in estimating present or future water use in restricted population
of city.

7. 3. Characteristics of population
Characteristics of population partially economic level, can produce
substantial variation for average use of 300 lpcd in high value districts
of city sub-urban communities with aa similar population per capita use
will be high. Watering lawn will increase this figure more. Lower use is
found in low value districts where sewerage is not provided and water
supply are inadequate.

8. 4. Metering of water
Metering of water supplies to individual user has been shown to reduced
consumption by 50%. In absence of meters user have no incentive to
conserve water and waste is much more common. Metering is also
desirable in that it permits analysis of use patterns of different classes of
users, thereby providing data which is useful in planning expansion of
facilities and in assessing the magnitude of loss due to leaks in
distribution system.

9. 5.Climate
During hot dry weather water consumption will increases as a result of
lawn watering and more bathing, during cold weather the consumption
of water tends to decrease.

10. 6. Quality
Water which of poor quality ( colored. Odor, and other objectionable)
will be use less than improvements in qualities of public supply are
likely to result in increase in consumption

11. 7. Pressure
High pressure in system also result in greater use in addition. It
increases losses from leaks, reducing water pressure can reduce per
capita use by 6%.

12. 8.Maintenance system
A well designed program of maintenance will reduce losses and wastes
in system.

13. 9. Conservation programs
Conservation programs may be either short term ( during drought) or
permanent. Such programs may limit or prohibit lawn watering,
encourage the use of drought resistant yard plantings. Encourage the use
of flow restricting showers, water saving toilets and similar devices and
apply rate of schedules in which the unit cost to consumer increases
with total use.

14. ❖Water demands for different purposes
❖Average daily demand: the total quantity of water supplied for a period of one year
divided by no of days in year. If this demand is based on a single person then it is average
per capita
Q=q/365xp
Here Q= discharge rate ( LPCD) ; q= total quantity of water in liters
p= population
❖Average daily demand (ADD):
ADD= Q/365xP
➢Maximum daily demand (MDD)= ADDx1.8
➢Maximum weekly demand (MWD)= ADDx1.48
➢Maximum hourly demand (MHD)= ADDx1.50
➢Maximum monthly demand(MMD) = ADDx1.28
➢Minimum rate of demand (MRD)=(0.25-0.50)X ADD
➢Peak hourly demand (PHD)= ADDx2.70

15. ❖Average daily consumption
• A rough estimate is
Use Percentage
Domestic 44%
Industrial 24%
Commercial 15%
Public 09%
Losses and wastes 8%

16. ❖Fire demand
Water required for fire fighting is called fire demand. Fire demand of water is
often the determining factor in the design of mains. Although the actual use
of water is less, the rate of use is high. Hydrant pressure should be more
than 140 Kpa where motor pump is used & more than 690 Kpa if pump is not
used. The insurance services office (ISO) use formula.
F = 320𝑋 𝐶√𝐴 (for M.K.S)
F = 18𝑋 𝐶√𝐴 (for F.P.S)
F= required flow in M3/day , gal/day
A= total floor area excluding basement
C=coefficient related to construction material

17. Value of C
Material of construction Value of c
Wood frame 1.5
Ordinary construction 1
Heavy timber type building 0.90
Non combustible construction 0.80
Fire resistive structure 0.60

18. Problem#01: A 5 story building of ordinary construction of 7700ft2 of ground
area communicating 3-story building of 9500ft2 ground area compute water
demand for fire.
Solution:
Data: n1=5 a1=7700 ft2
n2=3 a2=9500 ft2
C=1
Required: F=?
A= n1a1 + n2a2
A=(5x7700)+(3x9500)
A=38,500+28500
A=67000 ft2
F = 18𝑋 𝐶√𝐴
F= 18x1x√67000
F=4659 gal/mint ANS.

19. Problem#02: A 4 story building of heavy timber type of 715m2 of
ground floor area. Calculate water required for fire use ISO formula.
Solution:
Data: n=4 a=715m2
C=0.90
Required: F=?
A= n x a= 4x715= 2860m2
F = 320𝑋 𝐶√𝐴
F= 320x0.90x√2860
F=15401m3/day Ans.

20. National Board of fire Formula (NBF)
Q fire =3.86√p (1-0.01√p) SI units
Q fire =1020√p (1-0.01√p) FPS units
P= population in thousands
Q= discharge m3 /mint or gal/mint

21. Problem#03 assuming high value residential area of 100 ha has a housing density of
10 houses /ha with 4 persons per house hold the average daily demand is 340 l p c d.
Determine the water demand including fire demand
Solution:
Population = 100x10x4 = 4000 persons
Estimated daily flow = 4000x340
= 1360,000 lit/day
Maximum daily flow= 1.8 x ADD= 1.8x1360,000 l/day
= 24,48000 l/day /1000 = 2448 m3 /day.
Q fire =3.86√p (1-0.01√p)
= 3.86√4(1-0.01√4)
=7.56m3/mints x 60x24
Q fire =10894 m3 /day
Total demand= 2448+10894
Total demand = 13342 m3 /day

22. QUESTIONS & ANSWERS

23. THANKS