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6.6 Office Studies of Pipe Networks 205
the best processes can be so systematized as to make their application a matter of simple
arithmetic and pipe-flow tables, diagrams, or slide rules. Useful methods of analysis are:
1. Sectioning
2. Relaxation
3. Pipe equivalence
4. Computer programming and electrical analogy
6.6.1 Sectioning

Sectioning is an approximate and, in a sense, exploratory method, simple in concept and
application and widely useful provided its limitations are clearly understood. Similar in
concept is the circle method, which is usually confined to cutting pipes tributary to a cen-
tral fire hydrant or group of hydrants at the center of a circle.
Use of the section method is illustrated in Fig. 6.10 and Example 6.2. These are the
required steps:
1. Cut the network by a series of lines, not necessarily straight or regularly spaced but
chosen with due regard to the assumed sources and loads and the estimated loca-
tion of the piezometric contours. A first series of lines may well cut the distribution
piping substantially at right angles to the general direction of flow, that is, perpen-
dicular to a line drawn from the supply conduit to the high-value district (Fig. 6.7).
Further series may be oriented in some other critical direction, for example, hori-
zontally and vertically in Fig. 6.7. For more than one supply conduit, the sections
may be curved to intercept the flow from each conduit.
2. Estimate how much water must be supplied to areas beyond each section. Base esti-
mates on a knowledge of the population density and the general characteristics of the
zone: residential, commercial, and industrial. The water requirements comprise (a) the
normal, coincident draft, here called the domestic draft, and (b) the fire demand
(Table 4.13). Domestic use decreases progressively from section to section, as popula-
tion or industry is left behind; fire demand remains the same until the high-value district
has been passed, after which it drops to a figure applicable to the type of outskirt area.
a b

c 24˝
24˝
d
20˝ 20˝ 10˝
e
a
20˝ 20˝ 20˝ 10˝
b
20˝
8˝ 10˝ 10˝
12˝
12˝
12˝ 12˝ 12˝
c 16˝
8˝ 12˝ 12˝
12˝
d
8˝
8˝ 12˝
e
12˝
(a) (b)
Figure 6.10 Plan of Network Analyzed by Method of Sections Example 6.2 (a) Existing System;
(b) Recommended System (unless otherwise indicated, pipe diameters are 6 in. (150 mm). The
high-value district is cross-hatched). Conversion factor: 1 1 in. 25.4 mm