*3.1. Application Networks*

In this study, to consider various types of network, application networks of various layouts were designed for the same region. Specifically, as shown in Figures 2 and 3, for a region with 25 demand nodes distributed in a grid format, application networks were configured with 17 different layouts, which ranged from the most-looped P-41 layout with all of the 41 pipes arranged to the most-branched P-25 layout with only 25 pipes arranged. All 17 networks supply the 25 demand nodes from a single source with a total head of 45 m.

**Figure 2.** Configuration of application grid network (P-41).

**Figure 3.** Optimally designed application network layout.

Base demand at all nodes was equal at 9.49 m3/h, and 17 networks were designed by applying an hourly peaking factor (HPF) of 2.25 to produce design flow. Here, a multi-objective genetic algorithm (MOGA) was applied with decision variables of pipe layout and diameters, objective functions of design cost (minimization) and reliability indices (maximization), and a constraint of satisfying the minimum required pressure (15 m). Finally, 17 optimally designed networks were selected from the P-41 to P-25 layout considering distribution of reliability-index values. Figure 2 shows the node elevation and pipe length of the P-41 network, and the optimal layouts of the P-40–P-25 networks can be comprehensively viewed in Figure 3.
