Water and Wastewater Engineering
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17-40 WATER AND WASTEWATER ENGINEERING
Research by Haas et al. (2002) has demonstrated that lined and unlined DIP requires larger
chlorine dos es than PVC pipe to achieve a 25 mg/L residual after 24 hours. The demand for
chlorine is larger for smaller diameter pipes than larger ones. F or example: the dose of calcium
hypochlorite to achieve a resid
ual of 25 mg/L after 24 hours is 44.0 mg/L for 100 mm diameter
versus 31.7 mg/L for 300 mm diameter.
17-9 CHAPTER REVIEW
When you have completed studying this chapter, you should be able to do the following without
the aid of your textbook or notes:
1 . Under the two common distribution systems design strategies (i.e., with and without
fire protection), describe the components of demand that must be estimated.
2. Explain why fire sprinkler systems reduce fire demand.
3. Explain why
it is not necessary to calculate the NFF for each building in a distribution
system.
4. State the normal range of pressures for a distribution system and the allowable
minimum pressure in units of kPa.
5. Identify the following abbreviations that are used for describing distribution pipe
material: DIP, PVC, HDPE, RCPP, ACP.
6. Explain the closu
re mechanism for the following valves: globe, gate, plug, butterfly.
7. Select the appropriate valve type for isolating pipe section and for regulating flow.
8. Explain the difference between pumped storage and float-on-the system storage.
9. Explain why very large communities frequently do not have elevated storage tanks.
10. Explain the difference between the riser pipe and overflow pipe in terms of func
tion
and location of its terminal point in the water tower.
11. Explain why mixing of water in a storage tank is desirable.
12. Describe one method for mixing the contents of storage tank.
W ith the aid of this text, you should be able to do the following:
13. Estimate the sprinkler and hose-stream fire flow for a given structure given a
description of the type of occupant and the floor area.
14. Estimate the N
FF for a building given the appropriate ISO tables or citations.
15. Estimate the demand for a distribution network district.
16. Perform a pipe network design and analysis for a small system that does not have any
loops.
Visit the text website at www.mhprofessional.com/wwe for supplementary materials
and a gallery of photos.
STORAGE AND DISTRIBUTION SYSTEMS 17-41
17. On a pipe network, locate the points where valves and hydrants should be placed.
18. Calculate minor losses in terms of headloss using either appropriate equations or equiv-
alent length of pipe.
19. Given a community plan and scenario for growth and fire protection, locate a water
tower.
20. Given a community plan and scenario for growth and fire protection, determine the
volume for a water tower.
21. Cal
culate the required inlet velocity to achieve a mixing time given the riser diameter
and the water temperature.
22. Calculate the required inlet volume (
D
V
) to achieve a mixing time that is less than the
fill time.
23. Calculate the minor losses for a given piping arrangement for a pump.
24. Perform a network analysis using EPANET.
17-10 PROBLEMS
17-1. Estimate the sprinkler and hose-stream fire flow for a warehouse that is used to store
books. The warehouse is one story with dimensions of 10 m 100 m.
17-2. A sprinkler system is to be designed for the Southern Cross Mall. The mall consists
of four corridors that join at the center as shown in Fig
ure P-17-2 . The anchor store at
the end of each corridor occupies 1,000 m
2
. The stores on both sides of the corridor
are of varying frontage, but each is 10 m in length. Determine the size of the sprinkler
districts to form the minimum number of districts and mark them on a copy of the
mall plan. Estimate the sprinkler and hose-stream fire flow for a sprinkler district.
200 m
Anchor
store
(1,000 m
2
)
FIGURE P-17-2
Southern Cross Mall.
17-3. Estimate the NFF for a subdivision of duplex buildings that are centered on lots that
are 30 m 30 m. The duplexes are 26 m 8 m. They are set on the lots so the long
dimension faces the street and the short dimensions face each other.
17-42 WATER AND WASTEWATER ENGINEERING
17-4. A client has requested that your firm examine the implications of building materials
on the motel model in Example 17-2 . Using the following coefficients from the ISO
tables, calculate the NFF and plot the NFF versus the construction class ( F ). Explain
the cost implication
s for capital cost versus the annual insurance cost.
Frame construction: F 1.5
Joisted masonry construction: F 1.0
M a sonry, noncombustible: F 0.8
Fire resistive: F 0.6
17-5. E stimate the demand
for the Village of Sunfield distribution network shown in
Figure P-17-5 . The population estimate is 1,380 people. No fire protection will
be provided. Assume the average daily withdrawal is the same as that for Nevada
(Table 2-6).
FIGURE P-17-5
Village of Sunfield distribution system.
100 mm
200 mm
200 mm 200 mm
Treatment
plant
150 mm
wells
Service area boundry
All pipes excep
t
those marked
are 150 mm
100 m
17-6. Rework Problem 17-5 assuming fire protection will be provided. Assume only resi-
dential housing and a distance of 15 m between houses.
17-7. Estimate the demand for the Village of Webster distribution network shown in
Figure P-17-7 . The population estimate is 1,690 people. No fire protection will be
provided. Assume the average daily withdrawal is the
same as that for Connecticut
(Table 2-6).
STORAGE AND DISTRIBUTION SYSTEMS 17-43
17-8. Rework Problem 17-7 assuming fire protection will be provided. Assume only resi-
dential housing and a distance of 3 m between houses.
17-9. Rework Example 17-4 by adjusting the pipe sizes rather than the elevation of the
storage tank to achieve a pressure of 207 kPa at Point H.
17-10. Perform a hydraulic analysis on the camp in Example 17-4 to find the pressure at
Point F.
17-11. A water distribution system is being designed to supply a valley community as
shown in Figure P-17-11. Assuming that minor losses and friction can be ignored,
does the pressure at the critical points B and C in the system meet specification
norms?
17-12. Determine the losses
(total of friction and minor in meters of head) in the pipe shown
in Problem 17-11 for the following conditions: pipe diameter 200 mm, flow
rate 227 m
3
/h, pipe length 170.7 m; pipe has one ordinary entrance, one gate
valve fully open, two long sweep elbows.
17-13. In order to reduce its insurance rate, a country club has proposed that they build a water
line from the city trunk line as shown in Figure P-17-13. As the city engineer, you must
verify that there is enough press
ure in the trunk line to ensure that the required fire flow
FIGURE P-17-7
Village of Webster distribution system.
100 mm 100 mm
100 mm
100 mm
100 mm100 mm
100 mm
100 mm
100 mm
100 mm
200 mm
200 mm
Well
All pipes except
those marked
are 150 mm
100 m
Service area boundary
17-44 WATER AND WASTEWATER ENGINEERING
FIGURE P-17-11
Valley water distribution system.
6.0 m
A
Elevation = 106.7 m
Elevation = 0.0 m
Elevation 61.0 m
Water main
Water main = 200 mm
Q = 113.5 m
3
/h
Pipe lengths AB = 152.4 m
BC = 152.4 m
Pipe is 1.5 m below ground at all locations
Water main
B
C
FIGURE P-17-13
Water main for fire flow.
1.5 m
1.6 km
600 mm
200 mm
0.40 m/m
Sudden contraction
Standard tee
Hydrant loss = 34.5 kPa
150 mm
of 136 m
3
/h can be delivered at a pressure of 206 kPa after it leaves the hydrant. Calcu-
late the required pressure in the trunk line. Show all work. Include minor losses.
17-14. In anticipation of a commitment to provide fire protection, on a copy of the map of
Sunfield’s distribution system (Problem 17-5), mark the locations where valves and
fire hydrants should be plac
ed.
17-15. In anticipation of a commitment to provide fire protection, on a copy of the map of
Webster’s distribution system in Problem 17-7, mark the locations where valves and
fire hydrants should be placed.
STORAGE AND DISTRIBUTION SYSTEMS 17-45
17-16. On a copy of the map of Sunfield’s distribution system (Problem 17-5), mark the
location where an elevated storage tank should be placed. Assume that the village
anticipates growth to the west that will double the population in 20 years.
17-17. On a copy of the map of Webster’s distribution system (Problem 17-7), mark the
location of an elevated s
torage tank. Assume that the village anticipates no growth in
the foreseeable future.
17-18. Lotta Doubts has estimated that an elevated water storage tank for the Village of
Doom should have a capacity of 4,540 m
3
. Doom has a population of 5,000. Based
on historic records, the average daily demand is 380 Lpcd and the maximum daily
demand is estimated to be two times the average daily demand. Neither the popula-
tion nor the demand is expected to change over the next 2
5 years. The fire demand is
estimated at 570 m
3
/h for a two-hour fire. The village is supplied by two well pumps.
Each can pump at 90 m
3
/h. As the senior engineer, you are to check Lotta’s work.
Show by calculation that she is either correct or incorrect. Assume that there is no
other storage tank, no emergency supply, and no nearby water body or fire depart-
ment tanker truck.
17-19. Determine the volume of an elevated water storage tank required for the Village of
Sunfield (Problem 17-5). Assume backup power and a
dditional wells will be con-
structed as the population doubles to 2,760 people. Fire protection is to be provided
and off-peak pumping will be provided for equalization. Select an appropriate tank
from Figure P-17-19. On a copy of the tank drawing, annotate the drawing for miss-
ing appurtenances and/or appurtenance specifications.
17-20. Determine the volume of an elevated water storage tank required
for the Village of
Webster (Problem 17-7). Assume there is backup power and a constant population.
Fire protection is to be provided and off-peak pumping will be provided for equaliza-
tion. Select an appropriate tank from Figure P-17-19. On a copy of the tank drawing,
annotate the drawing for missing appurtenances and/or appurtenance specifications.
17-21. Determine whether or not the fill time for the Village of Sunfield’s s
torage tank
(Problem 17-19) exceeds the mixing time using the following assumptions:
1 . One pump can meet the maximum day demand in 12 hours.
2. The diameter of the inlet is 300 mm.
17-22. Determine whether or not the fill time for the Village of Webster’s storage tank
(Problem 17-20) exceeds the mixing time using the following assum
ptions:
1 . One pump can meet the maximum day demand in 12 hours.
2. The diameter of the inlet is 300 mm.
17-23. Design a water distribution system for the Bastogne Retirement Center (Figure P-17-23).
The specific design requirements of the client are as follows:
a . Fire protection to be provid
ed by the water distribution system.
b . Minimum water pressure at the top of the apartment building is to be 240 kPa.
c. Maximum system pressure is to be 550 kPa.
17-46 WATER AND WASTEWATER ENGINEERING
The following assumptions may be used in the design:
a . Each of the three apartment buildings is occupied by 50 residents. Each apartment
building is four stories high. Each story is 3 m high.
b . Each duplex is occupied by four resi
dents.
c. Average daily demand for the Center is 500 Lpcd.
d. Peaking factor is 6.8 for peak hour demand.
e. Needed fire flow for the duplexes is 230 m
3
/h.
f . Needed fire flow for an apartment building is 500 m
3
/h.
FIGURE P-17-19
T ypical elevated storage tanks.
Standard sizes
Watersphere tanks
Waterspheroid tanks
Rainproof roof
hatches
Rainproof roof
hatches
Top capacity line
Top capacity line
Tank access ladder
Tank access ladder
Roof access ladder
Roof access ladder
A
cc
e
ss
t
ube
Bottom capacity line
Bottom capacity line
Painters rings
Painters rings
Ladder
Ladder
Condensate ceiling
(Optional)
Condensate ceiling
(Optional)
Valve pit
Valve pit
Base bend
Base bend
Grade
Grade
Door
Door
Access tube
Ventilation hatch
Ventilation hatch
Platform
Platform
Painters hatch
Painters hatch
Riser pipe
Riser pipe
Overflow pipe
to gro
und
Overflow pipe
to ground
Expansion joint
Expansion joint
Capacity
Range of
head
Diameter
of sphere
95
114
5.80
6.15
6.74
7.21
8.24
9.02
9.71
10.32
151
189
284
379
473
568
5.02
5.38
6.05
6.60
7.68
8.69
9.33
9.95
m
3
mm
Capacity
Range of
head
757
946
1,135
1,515
1,890
2,840
3,785
4,730
5,680
7,570
12.35
13.31
14.18
15.71
16.93
19.70
22.55
24.04
26.37
28.58
8.76
9.53
9.91
10.68
11.43
12.20
12.20
13.42
14.02
15.85
m
3
m
Diameter
of sphere
m
STORAGE AND DISTRIBUTION SYSTEMS 17-47
g . System pressure is to be provided from the elevated storage tank.
h. Other than static lift, pressure loses in buildings may be ignored.
i. The distribution system will not contain any loops.
To satisfactorily complete the design, you must provide the following:
a . A design table s
imilar to that used in Example 17-4 showing the pipe diameters
and pressures at critical points (e.g., high and low elevations, and end of pipe).
b . A standard size storage tank from Figure P-17-19, the volume of the storage tank,
the minimum and maximum elevations (above MSL and above grade) of water in
the storage tank.
c. Locate fire hydrant
s and valves on a copy of the water line map (Figure P-17-23).
17-24. Design a water distribution system for the Village of Waffle ( Figure P-17-24 on page
17-49). The specific design requirements of the client are as follows:
a . Fire protection to be provided by the water distribution system.
b . Minimum water pressure at top of apartment building is to be 240 kPa.
c. Maximum system pressure is to be 550 kPa.
The following assumptions may be used in the design:
a . Each of the four apartment buildings is occupied by 50 residents. Each apartment
building is four stories high. Each story is 3 m high.
b . Each house is occupied by three resident
s.
c. Average daily demand for the Village is 500 Lpcd.
d. Peaking factor is 6.2 for peak hour demand.
e. Needed fire flow for the houses is 230 m
3
/h.
f . Needed fire flow for an apartment building is 500 m
3
/h.
g . System pressure is to be provided from the elevated storage tank.
h. Other than static lift, pressure losses in buildings may be ignored.
i. The distribution system will not contain any loops.
To satisfactorily complete the design, you must provide the following:
a . A design table
similar to that used in Example 17-4 showing the pipe diameters
and pressures at critical points (e.g., high and low elevations, and end of pipe).
b . A standard size storage tank from Figure P-17-19, the volume of the storage tank,
the minimum and maximum elevations (above mean sea level (MSL) and above
grade) of water in the storage tank.
c.
Locate fire hydrants and valves on a copy of the water line map (Figure P-17-24).
17-25. Using EPANET, determine the pressure at point G in the skeletonized system shown
in Figure P-17-25 on page 17-50 . The flow rate shown is the fire demand plus the
domestic flow. Is the pressure adequate for fire supply? Assume that the elevations at
all of the junctions are the
same.
17-48 WATER AND WASTEWATER ENGINEERING
F
u
tu
re
Fu
t
u
r
e roa
d
s
ewer
100 yr. flood
400 m
485 m
Future golf course
D1
D2
D4
D6
D9
D5
D7
D8
D10
D12
D14
D11
D13
D15
D3
4
8
0
m
1
0
0
y
r
.
f
l
o
o
d
Water
490 m
495 m
N
480
m
GS
CS
L
Parking
lot
48
5
m
485
m
Grd. El. 490 m
490 m
495 m
500 m
Water
Storage
Grd. El.
Well
Bldg.
1
Bldg.
3
Bl
d
g.
2
Parking
lot
C. H
BH
Pool
Tennis
courts
Sewer
475
m
Siphon inlet
Mos
elle river
Water main
Sewer
Scale :
50 m
FIGURE P-17-23
Bastogne Retirement Center.
STORAGE AND DISTRIBUTION SYSTEMS 17-49
17-26. Using EPANET, determine the pressure at point A in the skeletonized system shown
in Figure P-17-26 . The flow rate shown is the fire demand plus the domestic flow. Is
the pressure adequate for fire supply? Assume that the elevations at all of the junc-
tions are the same.
17-27. Estimate the total minor losses for the pipe and pump system
shown in Figure 17-15
and Table 17-10 . Assume the flow rate is 15.1 m
3
/ min. Use the loss coefficient method
( K ) to make the estimate. Use gate valves in place of the butterfly valves. Assume a
Hazen-Williams C of 140 for the pipe sections.
17-28. Repeat Problem 17-23 using the equivalent length of pipe method.
N
1
3
6
m
128
m
Water tower
Grd El 137 m
120
m
112
m
104
m
112
m
120
m
100 m
120 m
120 m
128 m
State Roa
d
C
o
f
f
e
e
C
r
e
e
k
1
0
0
–
Y
e
a
r
f
l
o
o
d
120
m
E
gg
s
Roa
d
Apartments
Ba
c
on Roa
d
Pan
c
ake Roa
d
128
m
128
m
S
yr
up River
S
y
r
u
p River
FIGURE P-17-24
Village of Waffle.