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(b) How many distribution lines (minimum) should be upgraded
13 L/s
172 L/s
from 8 in. to 10 in. in order to maintain a residual pressure of
D
G
A
at least 20 psi at the hydrants?
A
8 L/s
16 L/s
26 L/s
B
E
H
600 ft
F
I
C
3
s / L
8
s / L
1
s / L
6 24 L/s Chapter 6 Water Distribution Systems: Components, Design, and Operation 600 ft B
4
Figure 6.28 Water network for Problem 6.12. X 3000 ft
The pressure at point A is 230 kPa and C for all pipes is 100.
If the maximum allowable head loss in the system is 2.5‰, find
(a) Diameter of pipe AB.
(b) Diameter of pipe CF.
(c) Diameter of pipe DG.
(d) Diameter of pipe HI. D C
(e) The minimum possible pressure at point I. 3000 ft
6.13 Assuming water is to be delivered to a fire through not more
Figure 6.30 Water network for Problem 6.14.
than 500 ft of hose, find the water available (in gpm) for a fire in
the center of the loop shown in Fig. 6.29. All pipes are located at
6.15 The layout of a loop for a city water distribution system
the same elevation. The pressure in the 12 in. feeder pipes is 40 psi
located on a flat area is shown in Fig. 6.31. All pipes of the network
and the residual hydrant pressure is not to be less than 20 psi. C for
have a Hazen–Williams C of 100. The fire hose lines available are
all pipes is 100.
150 m long. If the residual pressure in the 300 mm mains is 300 kPa,
how much water (Q ) can be withdrawn for firefighting at the center
F
12 in. 12 in. of loop without lowering the residual pressure at the hydrants below
8 in. 6 in. 8 in. 6 in.
12 in. 150 kPa?
400 ft
500 ft
6 in. 3 0 0 m m 3 0 0 m m
150 mm 200 mm 150 mm
300 mm
6 in.
2000 ft X 200 m
200 mm
6 in.
200 m
6 in.
800 m X 150 mm
12 in.
200 mm
2500 ft
Figure 6.29 Water network for Problem 6.13.
300 mm
6.14 A gridiron layout of a distribution system located on a flat 800 m
area is shown in Fig. 6.30. All pipes of the network are made of
ductile iron (C = 100). The grid serves an area that requires a design Figure 6.31 Water network for Problem 6.15.
fire flow of 10,000 gpm. The pressure in the primary feeder mains
ABCDA is 35 psi. All distribution pipes are 8 in. in diameter. The 6.16 Mains of a city water distribution loop (ABCDA) are located
fire hose lines available are 400 ft long. at an elevation of 635 m (Fig. 6.32). All distribution pipes 1, 2, 3,
Supposing there is a fire at the middle of the grid (point x), 4, 5, and 6 have a diameter of 150 mm and a Hazen–Williams C of
(a) Find the residual pressure at the hydrants. 100. The fire hose lines available are 150 m long and the required