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226 Chapter 6 Water Distribution Systems: Components, Design, and Operation
(b) What is the minimum possible pressure at point I? Is 12 in. 12 in.
it acceptable? Assume that a pressure of 30 psi is 8 in. 6 in. 8 in. 6 in. 12 in.
available at point A. 400 ft
6.12 The elevations at various points in the water distribution 500 ft 6 in.
system shown in Fig. 6.28 are as follows:

A, B, and D 528.5 m 6 in.
C, E, and G 530.0 m
2,000 ft X
F and H 531.5 m
6 in.
I 532.5 m
6 in.
24 L/s 13 L/s 172 L/s
G D A
12 in.

8 L/s 16 L/s 26 L/s 2,500 ft
Figure 6.29 Water Network for Problem 6.13
B
H E
pipes is 40 psi and the residual hydrant pressure is not to be less
than 20 psi. C for all pipes is 100.
6.14 A gridiron layout of a distribution system located on a flat
I F C area is shown in Fig. 6.30. All pipes of the network are made of
63 L/s 8 L/s 14 L/s ductile iron (C 100). The grid serves an area that requires a
design fire flow of 10,000 gpm. The pressure in the primary
Figure 6.28 Water Network for Problem 6.12
feeder mains ABCDA is 35 psi. All distribution pipes are 8 in.
in diameter. The fire hose lines available are 400 ft long.
The known lengths and diameters of pipes are as shown
below: Supposing there is a fire at the middle of the grid (point x):
(a) Find the residual pressure at the hydrants.
Pipe d (mm) L (m)
(b) How many distribution lines (minimum) should be
AB d AB 200 upgraded from 8 in. to 10 in. in order to maintain a
BC 250 200 residual pressure of at least 20 psi at the hydrants?
DE 200 200
EF 150 200 A B
GH 300 200
HI d HI 200 600 ft
AD 400 500
BE 200 500 600 ft
CF d CF 500
DG d DG 600
EH 150 600
FI 200 600
X 3,000 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.
(e) The minimum possible pressure at point I.
6.13 Assuming water is to be delivered to a fire through not D C
more than 500 ft of hose, find the water available (in gpm) for a 3,000 ft
fire in the center of the loop shown in Fig. 6.29. All pipes are
located at the same elevation. The pressure in the 12-in. feeder Figure 6.30 Water Network for Problem 6.14